Remove ZK 3.9.1

26 files changed, 16 insertions, 8177 deletions

diff --git a/zookeeper-server/pom.xml b/zookeeper-server/pom.xml
index 4b7f4be7a7f..e0838a9eefa 100644
--- a/zookeeper-server/pom.xml
+++ b/zookeeper-server/pom.xml
@@ -14,7 +14,6 @@
   <modules>
     <module>zookeeper-server-common</module>
     <module>zookeeper-server</module>
-    <module>zookeeper-server-3.9.2</module>
   </modules>
   <dependencies>
     <dependency>
diff --git a/zookeeper-server/zookeeper-server-3.9.2/CMakeLists.txt b/zookeeper-server/zookeeper-server-3.9.2/CMakeLists.txt
deleted file mode 100644
index de5780610d9..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/CMakeLists.txt
+++ /dev/null
@@ -1,2 +0,0 @@
-# Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-install_jar(zookeeper-server-3.9.2-jar-with-dependencies.jar)
diff --git a/zookeeper-server/zookeeper-server-3.9.2/pom.xml b/zookeeper-server/zookeeper-server-3.9.2/pom.xml
deleted file mode 100644
index 791c026234a..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/pom.xml
+++ /dev/null
@@ -1,99 +0,0 @@
-<?xml version="1.0"?>
-<!-- Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root. -->
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
-  <modelVersion>4.0.0</modelVersion>
-  <parent>
-    <groupId>com.yahoo.vespa</groupId>
-    <artifactId>zookeeper-server-parent</artifactId>
-    <version>8-SNAPSHOT</version>
-    <relativePath>../pom.xml</relativePath>
-  </parent>
-  <artifactId>zookeeper-server-3.9.2</artifactId>
-  <packaging>container-plugin</packaging>
-  <version>8-SNAPSHOT</version>
-  <properties>
-    <zookeeper.version>3.9.2</zookeeper.version>
-  </properties>
-  <dependencies>
-    <dependency>
-      <groupId>com.yahoo.vespa</groupId>
-      <artifactId>zookeeper-server-common</artifactId>
-      <version>${project.version}</version>
-    </dependency>
-    <dependency>
-      <groupId>com.yahoo.vespa</groupId>
-      <artifactId>zookeeper-client-common</artifactId>
-      <version>${project.version}</version>
-      <exclusions>
-        <exclusion>
-          <!-- Don't use ZK version from zookeeper-client-common -->
-          <groupId>org.apache.zookeeper</groupId>
-          <artifactId>zookeeper</artifactId>
-        </exclusion>
-      </exclusions>
-    </dependency>
-    <dependency>
-      <groupId>org.apache.zookeeper</groupId>
-      <artifactId>zookeeper</artifactId>
-      <version>${zookeeper.version}</version>
-      <exclusions>
-        <!--
-          Container provides wiring for all common log libraries
-          Duplicate embedding results in various warnings being printed to stderr
-         -->
-        <exclusion>
-          <groupId>org.slf4j</groupId>
-          <artifactId>slf4j-api</artifactId>
-        </exclusion>
-      </exclusions>
-    </dependency>
-    <!-- snappy-java and metrics-core are included here
-         to be able to work with ZooKeeper 3.7.0 due to
-         class loading issues -->
-    <dependency>
-      <groupId>io.dropwizard.metrics</groupId>
-      <artifactId>metrics-core</artifactId>
-      <scope>compile</scope>
-      <exclusions>
-        <exclusion>
-          <groupId>org.slf4j</groupId>
-          <artifactId>slf4j-api</artifactId>
-        </exclusion>
-      </exclusions>
-    </dependency>
-    <dependency>
-      <groupId>org.xerial.snappy</groupId>
-      <artifactId>snappy-java</artifactId>
-      <scope>compile</scope>
-    </dependency>
-  </dependencies>
-  <build>
-    <plugins>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-compiler-plugin</artifactId>
-        <configuration>
-          <compilerArgs>
-            <!-- Turn off classfile warnings where spotbugs is pulled in transitively. -->
-            <arg>-Xlint:all</arg>
-            <arg>-Xlint:-classfile</arg>
-            <arg>-Werror</arg>
-          </compilerArgs>
-        </configuration>
-      </plugin>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-install-plugin</artifactId>
-      </plugin>
-      <plugin>
-        <groupId>com.yahoo.vespa</groupId>
-        <artifactId>bundle-plugin</artifactId>
-        <extensions>true</extensions>
-        <configuration>
-          <importPackage>com.sun.management</importPackage>
-          <bundleSymbolicName>zookeeper-server</bundleSymbolicName>
-        </configuration>
-      </plugin>
-    </plugins>
-  </build>
-</project>
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/ConfigServerZooKeeperServer.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/ConfigServerZooKeeperServer.java
deleted file mode 100644
index a7cd14c415f..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/ConfigServerZooKeeperServer.java
+++ /dev/null
@@ -1,45 +0,0 @@
-// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-package com.yahoo.vespa.zookeeper;
-
-import com.yahoo.cloud.config.ZookeeperServerConfig;
-import com.yahoo.component.AbstractComponent;
-import com.yahoo.component.annotation.Inject;
-import com.yahoo.vespa.zookeeper.server.VespaZooKeeperServer;
-
-import java.nio.file.Path;
-
-/**
- *
- * Server used for starting config server, needed to be able to have different behavior for hosted and
- * self-hosted Vespa (controlled by zookeeperServerConfig.dynamicReconfiguration).
- *
- * @author Harald Musum
- */
-public class ConfigServerZooKeeperServer extends AbstractComponent implements VespaZooKeeperServer {
-
-    private final VespaZooKeeperServer zooKeeperServer;
-
-    @Inject
-    public ConfigServerZooKeeperServer(ZookeeperServerConfig zookeeperServerConfig) {
-        this.zooKeeperServer = zookeeperServerConfig.dynamicReconfiguration()
-                ? new ReconfigurableVespaZooKeeperServer(new Reconfigurer(new VespaZooKeeperAdminImpl()), zookeeperServerConfig)
-                : new VespaZooKeeperServerImpl(zookeeperServerConfig);
-    }
-
-    @Override
-    public void deconstruct() { zooKeeperServer.shutdown(); }
-
-    @Override
-    public void shutdown() {
-        zooKeeperServer.shutdown();
-    }
-
-    @Override
-    public void start(Path configFilePath) {
-        zooKeeperServer.start(configFilePath);
-    }
-
-    @Override
-    public boolean reconfigurable() { return zooKeeperServer.reconfigurable(); }
-
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/ReconfigurableVespaZooKeeperServer.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/ReconfigurableVespaZooKeeperServer.java
deleted file mode 100644
index d869cbb6938..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/ReconfigurableVespaZooKeeperServer.java
+++ /dev/null
@@ -1,49 +0,0 @@
-// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-package com.yahoo.vespa.zookeeper;
-
-import ai.vespa.validation.Validation;
-import com.yahoo.cloud.config.ZookeeperServerConfig;
-import com.yahoo.component.AbstractComponent;
-import com.yahoo.component.annotation.Inject;
-import com.yahoo.vespa.zookeeper.server.VespaZooKeeperServer;
-
-import java.nio.file.Path;
-import java.time.Duration;
-
-/**
- * Starts or reconfigures zookeeper cluster.
- * The QuorumPeer conditionally created here is owned by the Reconfigurer;
- * when it already has a peer, that peer is used here in case start or shutdown is required.
- * Guarantees that server is up by writing a node to ZooKeeper successfully before
- * returning from constructor.
- *
- * @author hmusum
- */
-public class ReconfigurableVespaZooKeeperServer extends AbstractComponent implements VespaZooKeeperServer {
-
-    private QuorumPeer peer;
-
-    @Inject
-    public ReconfigurableVespaZooKeeperServer(Reconfigurer reconfigurer, ZookeeperServerConfig zookeeperServerConfig) {
-        Validation.require(zookeeperServerConfig.dynamicReconfiguration(),
-                           zookeeperServerConfig.dynamicReconfiguration(),
-                           "dynamicReconfiguration must be true");
-        peer = reconfigurer.startOrReconfigure(zookeeperServerConfig, this, () -> peer = new VespaQuorumPeer());
-    }
-
-    @Override
-    public void shutdown() {
-        peer.shutdown(Duration.ofMinutes(1));
-    }
-
-    @Override
-    public void start(Path configFilePath) {
-        peer.start(configFilePath);
-    }
-
-    @Override
-    public boolean reconfigurable() {
-        return true;
-    }
-
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/VespaMtlsAuthenticationProvider.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/VespaMtlsAuthenticationProvider.java
deleted file mode 100644
index 90554910293..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/VespaMtlsAuthenticationProvider.java
+++ /dev/null
@@ -1,48 +0,0 @@
-// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-package com.yahoo.vespa.zookeeper;
-
-import com.yahoo.security.X509SslContext;
-import com.yahoo.security.tls.TlsContext;
-import com.yahoo.security.tls.TransportSecurityUtils;
-import org.apache.zookeeper.KeeperException;
-import org.apache.zookeeper.common.ClientX509Util;
-import org.apache.zookeeper.common.X509Exception;
-import org.apache.zookeeper.data.Id;
-import org.apache.zookeeper.server.ServerCnxn;
-import org.apache.zookeeper.server.auth.AuthenticationProvider;
-import org.apache.zookeeper.server.auth.X509AuthenticationProvider;
-
-import javax.net.ssl.KeyManager;
-import javax.net.ssl.X509KeyManager;
-import javax.net.ssl.X509TrustManager;
-import java.security.cert.X509Certificate;
-import java.util.logging.Logger;
-
-/**
- * A {@link AuthenticationProvider} to be used in combination with Vespa mTLS.
- *
- * @author bjorncs
- */
-public class VespaMtlsAuthenticationProvider extends X509AuthenticationProvider {
-
-    private static final Logger log = Logger.getLogger(VespaMtlsAuthenticationProvider.class.getName());
-
-    public VespaMtlsAuthenticationProvider() {
-        super(null, null);
-    }
-
-    @Override
-    public KeeperException.Code handleAuthentication(ServerCnxn cnxn, byte[] authData) {
-        // Vespa's mTLS peer authorization rules are performed by the underlying trust manager implementation.
-        // The client is authorized once the SSL handshake has completed.
-        X509Certificate[] certificateChain = (X509Certificate[]) cnxn.getClientCertificateChain();
-        if (certificateChain == null || certificateChain.length == 0) {
-            log.warning("Client not authenticated - should not be possible with clientAuth=NEED");
-            return KeeperException.Code.AUTHFAILED;
-        }
-        X509Certificate certificate = certificateChain[0];
-        cnxn.addAuthInfo(new Id(getScheme(), certificate.getSubjectX500Principal().getName()));
-        return KeeperException.Code.OK;
-    }
-
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/VespaQuorumPeer.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/VespaQuorumPeer.java
deleted file mode 100644
index dd5ac4e252b..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/VespaQuorumPeer.java
+++ /dev/null
@@ -1,60 +0,0 @@
-// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-package com.yahoo.vespa.zookeeper;
-
-import com.yahoo.protect.Process;
-import org.apache.zookeeper.server.admin.AdminServer;
-import org.apache.zookeeper.server.quorum.QuorumPeerConfig;
-import org.apache.zookeeper.server.quorum.QuorumPeerMain;
-
-import java.io.IOException;
-import java.nio.file.Path;
-import java.time.Duration;
-import java.util.logging.Level;
-import java.util.logging.Logger;
-
-/**
- * Starts or stops a ZooKeeper server. Extends QuorumPeerMain to be able to call initializeAndRun() and wraps
- * exceptions so that it can be used by code that does not depend on ZooKeeper.
- *
- * @author hmusum
- */
-class VespaQuorumPeer extends QuorumPeerMain implements QuorumPeer {
-
-    private static final Logger log = java.util.logging.Logger.getLogger(VespaQuorumPeer.class.getName());
-
-    @Override
-    public void start(Path path) {
-        initializeAndRun(new String[]{ path.toFile().getAbsolutePath()});
-    }
-
-    @Override
-    public void shutdown(Duration timeout) {
-        if (quorumPeer != null) {
-            log.log(Level.FINE, "Shutting down ZooKeeper server");
-            try {
-                quorumPeer.shutdown();
-                quorumPeer.join(timeout.toMillis()); // Wait for shutdown to complete
-                if (quorumPeer.isAlive())
-                    throw new IllegalStateException("Peer still alive after " + timeout);
-            } catch (RuntimeException | InterruptedException e) {
-                // If shutdown fails, we have no other option than forcing the JVM to stop and letting it be restarted.
-                //
-                // When a VespaZooKeeperServer component receives a new config, the container will try to start a new
-                // server with the new config, this will fail until the old server is deconstructed. If the old server
-                // fails to deconstruct/shutdown, the new one will never start and if that happens forcing a restart is
-                // the better option.
-                Process.logAndDie("Failed to shut down ZooKeeper server properly, forcing shutdown", e);
-            }
-        }
-    }
-
-    @Override
-    protected void initializeAndRun(String[] args) {
-        try {
-            super.initializeAndRun(args);
-        } catch (QuorumPeerConfig.ConfigException | IOException | AdminServer.AdminServerException e) {
-            throw new RuntimeException("Exception when initializing or running ZooKeeper server", e);
-        }
-    }
-
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/VespaZooKeeperAdminImpl.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/VespaZooKeeperAdminImpl.java
deleted file mode 100644
index c74a020bcf4..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/VespaZooKeeperAdminImpl.java
+++ /dev/null
@@ -1,96 +0,0 @@
-// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-package com.yahoo.vespa.zookeeper;
-
-import com.yahoo.cloud.config.ZookeeperServerConfig;
-import com.yahoo.net.HostName;
-import com.yahoo.vespa.zookeeper.client.ZkClientConfigBuilder;
-import org.apache.zookeeper.CreateMode;
-import org.apache.zookeeper.KeeperException;
-import org.apache.zookeeper.ZooDefs;
-import org.apache.zookeeper.admin.ZooKeeperAdmin;
-import org.apache.zookeeper.data.ACL;
-import java.nio.charset.StandardCharsets;
-import java.time.Duration;
-import java.time.Instant;
-import java.util.List;
-import java.util.logging.Level;
-import java.util.logging.Logger;
-
-import static com.yahoo.yolean.Exceptions.uncheck;
-
-/**
- * @author hmusum
- */
-@SuppressWarnings("unused") // Created by injection
-public class VespaZooKeeperAdminImpl implements VespaZooKeeperAdmin {
-
-    private static final Logger log = java.util.logging.Logger.getLogger(VespaZooKeeperAdminImpl.class.getName());
-
-
-    @SuppressWarnings("try")
-    @Override
-    public void reconfigure(String connectionSpec, String servers) throws ReconfigException {
-        try (ZooKeeperAdmin zooKeeperAdmin = createAdmin(connectionSpec)) {
-            long fromConfig = -1;
-            // Using string parameters because the List variant of reconfigure fails to join empty lists (observed on 3.5.6, fixed in 3.7.0).
-            log.log(Level.INFO, "Applying ZooKeeper config: " + servers);
-            byte[] appliedConfig = zooKeeperAdmin.reconfigure(null, null, servers, fromConfig, null);
-            log.log(Level.INFO, "Applied ZooKeeper config: " + new String(appliedConfig, StandardCharsets.UTF_8));
-
-            // Verify by issuing a write operation; this is only accepted once new quorum is obtained.
-            List<ACL> acl = ZooDefs.Ids.OPEN_ACL_UNSAFE;
-            String node = zooKeeperAdmin.create("/reconfigure-dummy-node", new byte[0], acl, CreateMode.EPHEMERAL_SEQUENTIAL);
-            zooKeeperAdmin.delete(node, -1);
-
-            log.log(Level.INFO, "Verified ZooKeeper config: " + new String(appliedConfig, StandardCharsets.UTF_8));
-        }
-        catch (   KeeperException.ReconfigInProgress
-                | KeeperException.ConnectionLossException
-                | KeeperException.NewConfigNoQuorum  e) {
-            throw new ReconfigException(e);
-        }
-        catch (KeeperException | InterruptedException e) {
-            throw new RuntimeException(e);
-        }
-    }
-
-    private ZooKeeperAdmin createAdmin(String connectionSpec) {
-        return uncheck(() -> new ZooKeeperAdmin(connectionSpec, (int) sessionTimeout().toMillis(),
-                                                (event) -> log.log(Level.FINE, event.toString()), new ZkClientConfigBuilder().toConfig()));
-    }
-
-    /** Creates a node in zookeeper, with hostname as part of node name, this ensures that server is up and working before returning */
-    @SuppressWarnings("try")
-    void createDummyNode(ZookeeperServerConfig zookeeperServerConfig) {
-        int sleepTime = 2_000;
-        try (ZooKeeperAdmin zooKeeperAdmin = createAdmin(localConnectionSpec(zookeeperServerConfig))) {
-            Instant end = Instant.now().plus(Duration.ofMinutes(5));
-            Exception exception = null;
-            do {
-                try {
-                    zooKeeperAdmin.create("/dummy-node-" + HostName.getLocalhost(), new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
-                    return;
-                } catch (KeeperException e) {
-                    if (e instanceof KeeperException.NodeExistsException) {
-                        try {
-                            zooKeeperAdmin.setData("/dummy-node-" + HostName.getLocalhost(), new byte[0], -1);
-                            return;
-                        } catch (KeeperException ex) {
-                            log.log(Level.FINE, e.getMessage());
-                            Thread.sleep(sleepTime);
-                            continue;
-                        }
-                    }
-                    log.log(Level.FINE, e.getMessage());
-                    exception = e;
-                    Thread.sleep(sleepTime);
-                }
-            } while (Instant.now().isBefore(end));
-            throw new RuntimeException("Unable to create dummy node: ", exception);
-        } catch (InterruptedException e) {
-            throw new RuntimeException(e);
-        }
-    }
-
-}
-
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/VespaZooKeeperServerImpl.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/VespaZooKeeperServerImpl.java
deleted file mode 100644
index 4f93eb0efa5..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/com/yahoo/vespa/zookeeper/VespaZooKeeperServerImpl.java
+++ /dev/null
@@ -1,56 +0,0 @@
-// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-package com.yahoo.vespa.zookeeper;
-
-import ai.vespa.validation.Validation;
-import com.yahoo.cloud.config.ZookeeperServerConfig;
-import com.yahoo.component.AbstractComponent;
-import com.yahoo.component.annotation.Inject;
-import com.yahoo.vespa.zookeeper.server.VespaZooKeeperServer;
-
-import java.nio.file.Path;
-import java.time.Duration;
-
-/**
- * ZooKeeper server. Guarantees that the server is up by writing a node to ZooKeeper successfully before
- * returning from constructor.
- *
- * @author Ulf Lilleengen
- * @author Harald Musum
- */
-public class VespaZooKeeperServerImpl extends AbstractComponent implements VespaZooKeeperServer {
-
-    private final VespaQuorumPeer peer;
-    private final ZooKeeperRunner runner;
-
-    @Inject
-    public VespaZooKeeperServerImpl(ZookeeperServerConfig zookeeperServerConfig) {
-        Validation.require(! zookeeperServerConfig.dynamicReconfiguration(),
-                           ! zookeeperServerConfig.dynamicReconfiguration(),
-                           "dynamicReconfiguration must be false");
-        this.peer = new VespaQuorumPeer();
-        this.runner = new ZooKeeperRunner(zookeeperServerConfig, this);
-        new VespaZooKeeperAdminImpl().createDummyNode(zookeeperServerConfig);
-    }
-
-    @Override
-    public void deconstruct() {
-        runner.shutdown();
-        super.deconstruct();
-    }
-
-    @Override
-    public void shutdown() {
-        peer.shutdown(Duration.ofMinutes(1));
-    }
-
-    @Override
-    public void start(Path configFilePath) {
-        peer.start(configFilePath);
-    }
-
-    @Override
-    public boolean reconfigurable() {
-        return false;
-    }
-
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/common/ClientX509Util.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/common/ClientX509Util.java
deleted file mode 100644
index f6dfb0fa4d9..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/common/ClientX509Util.java
+++ /dev/null
@@ -1,230 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.zookeeper.common;
-
-import com.yahoo.vespa.zookeeper.tls.VespaZookeeperTlsContextUtils;
-import io.netty.handler.ssl.DelegatingSslContext;
-import io.netty.handler.ssl.SslContext;
-import io.netty.handler.ssl.SslContextBuilder;
-import io.netty.handler.ssl.SslProvider;
-import javax.net.ssl.KeyManager;
-import javax.net.ssl.SSLEngine;
-import javax.net.ssl.SSLException;
-import javax.net.ssl.SSLParameters;
-import javax.net.ssl.TrustManager;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import java.util.List;
-
-/**
- * X509 utilities specific for client-server communication framework.
- * <p>
- * <em>Modified to use Vespa's TLS context, whenever it is available, instead of the file-based key and trust stores of ZK 3.9.
- * Based on https://github.com/apache/zookeeper/blob/branch-3.9/zookeeper-server/src/main/java/org/apache/zookeeper/common/ClientX509Util.java</em>
- *
- * @author jonmv
- */
-public class ClientX509Util extends X509Util {
-
-    private static final Logger LOG = LoggerFactory.getLogger(ClientX509Util.class);
-
-    private final String sslAuthProviderProperty = getConfigPrefix() + "authProvider";
-    private final String sslProviderProperty = getConfigPrefix() + "sslProvider";
-
-    @Override
-    protected String getConfigPrefix() {
-        return "zookeeper.ssl.";
-    }
-
-    @Override
-    protected boolean shouldVerifyClientHostname() {
-        return false;
-    }
-
-    public String getSslAuthProviderProperty() {
-        return sslAuthProviderProperty;
-    }
-
-    public String getSslProviderProperty() {
-        return sslProviderProperty;
-    }
-
-    public SslContext createNettySslContextForClient(ZKConfig config)
-            throws X509Exception.KeyManagerException, X509Exception.TrustManagerException, SSLException {
-        SslContextBuilder sslContextBuilder = SslContextBuilder.forClient();
-        KeyManager km;
-        TrustManager tm;
-        if (VespaZookeeperTlsContextUtils.tlsContext().isPresent()) {
-            km = VespaZookeeperTlsContextUtils.tlsContext().get().sslContext().keyManager();
-            tm = VespaZookeeperTlsContextUtils.tlsContext().get().sslContext().trustManager();
-        }
-        else {
-            String keyStoreLocation = config.getProperty(getSslKeystoreLocationProperty(), "");
-            String keyStorePassword = getPasswordFromConfigPropertyOrFile(config, getSslKeystorePasswdProperty(),
-                                                                          getSslKeystorePasswdPathProperty());
-            String keyStoreType = config.getProperty(getSslKeystoreTypeProperty());
-
-            if (keyStoreLocation.isEmpty()) {
-                LOG.warn("{} not specified", getSslKeystoreLocationProperty());
-                km = null;
-            }
-            else {
-                km = createKeyManager(keyStoreLocation, keyStorePassword, keyStoreType);
-            }
-
-            tm = getTrustManager(config);
-        }
-
-        if (km != null) {
-            sslContextBuilder.keyManager(km);
-        }
-        if (tm != null) {
-            sslContextBuilder.trustManager(tm);
-        }
-
-        sslContextBuilder.enableOcsp(config.getBoolean(getSslOcspEnabledProperty()));
-        sslContextBuilder.protocols(getEnabledProtocols(config));
-        Iterable<String> enabledCiphers = getCipherSuites(config);
-        if (enabledCiphers != null) {
-            sslContextBuilder.ciphers(enabledCiphers);
-        }
-        sslContextBuilder.sslProvider(getSslProvider(config));
-
-        SslContext sslContext1 = sslContextBuilder.build();
-
-        if (getFipsMode(config) && isServerHostnameVerificationEnabled(config)) {
-            return addHostnameVerification(sslContext1, "Server");
-        } else {
-            return sslContext1;
-        }
-    }
-
-    public SslContext createNettySslContextForServer(ZKConfig config)
-            throws X509Exception.SSLContextException, X509Exception.KeyManagerException, X509Exception.TrustManagerException, SSLException {
-        KeyManager km;
-        TrustManager tm;
-        if (VespaZookeeperTlsContextUtils.tlsContext().isPresent()) {
-            km = VespaZookeeperTlsContextUtils.tlsContext().get().sslContext().keyManager();
-            tm = VespaZookeeperTlsContextUtils.tlsContext().get().sslContext().trustManager();
-        }
-        else {
-            String keyStoreLocation = config.getProperty(getSslKeystoreLocationProperty(), "");
-            String keyStorePassword = getPasswordFromConfigPropertyOrFile(config, getSslKeystorePasswdProperty(),
-                                                                          getSslKeystorePasswdPathProperty());
-            String keyStoreType = config.getProperty(getSslKeystoreTypeProperty());
-
-            if (keyStoreLocation.isEmpty()) {
-                throw new X509Exception.SSLContextException(
-                        "Keystore is required for SSL server: " + getSslKeystoreLocationProperty());
-            }
-            km = createKeyManager(keyStoreLocation, keyStorePassword, keyStoreType);
-            tm = getTrustManager(config);
-        }
-        return createNettySslContextForServer(config, km, tm);
-    }
-
-    public SslContext createNettySslContextForServer(ZKConfig config, KeyManager keyManager, TrustManager trustManager) throws SSLException {
-        SslContextBuilder sslContextBuilder = SslContextBuilder.forServer(keyManager);
-
-        if (trustManager != null) {
-            sslContextBuilder.trustManager(trustManager);
-        }
-
-        sslContextBuilder.enableOcsp(config.getBoolean(getSslOcspEnabledProperty()));
-        sslContextBuilder.protocols(getEnabledProtocols(config));
-        sslContextBuilder.clientAuth(getClientAuth(config).toNettyClientAuth());
-        Iterable<String> enabledCiphers = getCipherSuites(config);
-        if (enabledCiphers != null) {
-            sslContextBuilder.ciphers(enabledCiphers);
-        }
-        sslContextBuilder.sslProvider(getSslProvider(config));
-
-        SslContext sslContext1 = sslContextBuilder.build();
-
-        if (getFipsMode(config) && isClientHostnameVerificationEnabled(config)) {
-            return addHostnameVerification(sslContext1, "Client");
-        } else {
-            return sslContext1;
-        }
-    }
-
-    private SslContext addHostnameVerification(SslContext sslContext, String clientOrServer) {
-        return new DelegatingSslContext(sslContext) {
-            @Override
-            protected void initEngine(SSLEngine sslEngine) {
-                SSLParameters sslParameters = sslEngine.getSSLParameters();
-                sslParameters.setEndpointIdentificationAlgorithm("HTTPS");
-                sslEngine.setSSLParameters(sslParameters);
-                if (LOG.isDebugEnabled()) {
-                    LOG.debug("{} hostname verification: enabled HTTPS style endpoint identification algorithm", clientOrServer);
-                }
-            }
-        };
-    }
-
-    private String[] getEnabledProtocols(final ZKConfig config) {
-        String enabledProtocolsInput = config.getProperty(getSslEnabledProtocolsProperty());
-        if (enabledProtocolsInput == null) {
-            return new String[]{ config.getProperty(getSslProtocolProperty(), DEFAULT_PROTOCOL) };
-        }
-        return enabledProtocolsInput.split(",");
-    }
-
-    private X509Util.ClientAuth getClientAuth(final ZKConfig config) {
-        return X509Util.ClientAuth.fromPropertyValue(config.getProperty(getSslClientAuthProperty()));
-    }
-
-    private Iterable<String> getCipherSuites(final ZKConfig config) {
-        String cipherSuitesInput = config.getProperty(getSslCipherSuitesProperty());
-        if (cipherSuitesInput == null) {
-            if (getSslProvider(config) != SslProvider.JDK) {
-                return null;
-            }
-            return List.of(X509Util.getDefaultCipherSuites());
-        } else {
-            return List.of(cipherSuitesInput.split(","));
-        }
-    }
-
-    public SslProvider getSslProvider(ZKConfig config) {
-        return SslProvider.valueOf(config.getProperty(getSslProviderProperty(), "JDK"));
-    }
-
-    private TrustManager getTrustManager(ZKConfig config) throws X509Exception.TrustManagerException {
-        String trustStoreLocation = config.getProperty(getSslTruststoreLocationProperty(), "");
-        String trustStorePassword = getPasswordFromConfigPropertyOrFile(config, getSslTruststorePasswdProperty(),
-                                                                        getSslTruststorePasswdPathProperty());
-        String trustStoreType = config.getProperty(getSslTruststoreTypeProperty());
-
-        boolean sslCrlEnabled = config.getBoolean(getSslCrlEnabledProperty());
-        boolean sslOcspEnabled = config.getBoolean(getSslOcspEnabledProperty());
-        boolean sslServerHostnameVerificationEnabled = isServerHostnameVerificationEnabled(config);
-        boolean sslClientHostnameVerificationEnabled = isClientHostnameVerificationEnabled(config);
-
-        if (trustStoreLocation.isEmpty()) {
-            LOG.warn("{} not specified", getSslTruststoreLocationProperty());
-            return null;
-        } else {
-            return createTrustManager(trustStoreLocation, trustStorePassword, trustStoreType,
-                                      sslCrlEnabled, sslOcspEnabled, sslServerHostnameVerificationEnabled,
-                                      sslClientHostnameVerificationEnabled, getFipsMode(config));
-        }
-    }
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/common/NetUtils.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/common/NetUtils.java
deleted file mode 100644
index baa69f12968..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/common/NetUtils.java
+++ /dev/null
@@ -1,94 +0,0 @@
-// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-/*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.zookeeper.common;
-
-import java.net.Inet6Address;
-import java.net.InetAddress;
-import java.net.InetSocketAddress;
-
-/**
- * This class contains common utilities for netstuff. Like printing IPv6 literals correctly
- */
-public class NetUtils {
-
-    // Note: Changed from original to use hostname from InetSocketAddress if there exists one
-    public static String formatInetAddr(InetSocketAddress addr) {
-        String hostName = addr.getHostName();
-        if (hostName != null) {
-            return String.format("%s:%s", hostName, addr.getPort());
-        }
-
-        InetAddress ia = addr.getAddress();
-
-        if (ia == null) {
-            return String.format("%s:%s", addr.getHostString(), addr.getPort());
-        }
-        if (ia instanceof Inet6Address) {
-            return String.format("[%s]:%s", ia.getHostAddress(), addr.getPort());
-        } else {
-            return String.format("%s:%s", ia.getHostAddress(), addr.getPort());
-        }
-    }
-
-    /**
-     * Separates host and port from given host port string if host port string is enclosed
-     * within square bracket.
-     *
-     * @param hostPort host port string
-     * @return String[]{host, port} if host port string is host:port
-     * or String[] {host, port:port} if host port string is host:port:port
-     * or String[] {host} if host port string is host
-     * or String[]{} if not a ipv6 host port string.
-     */
-    public static String[] getIPV6HostAndPort(String hostPort) {
-        if (hostPort.startsWith("[")) {
-            int i = hostPort.lastIndexOf(']');
-            if (i < 0) {
-                throw new IllegalArgumentException(
-                    hostPort + " starts with '[' but has no matching ']'");
-            }
-            String host = hostPort.substring(1, i);
-            if (host.isEmpty()) {
-                throw new IllegalArgumentException(host + " is empty.");
-            }
-            if (hostPort.length() > i + 1) {
-                return getHostPort(hostPort, i, host);
-            }
-            return new String[] { host };
-        } else {
-            //Not an IPV6 host port string
-            return new String[] {};
-        }
-    }
-
-    private static String[] getHostPort(String hostPort, int indexOfClosingBracket, String host) {
-        // [127::1]:2181 , check separator : exits
-        if (hostPort.charAt(indexOfClosingBracket + 1) != ':') {
-            throw new IllegalArgumentException(hostPort + " does not have : after ]");
-        }
-        // [127::1]: scenario
-        if (indexOfClosingBracket + 2 == hostPort.length()) {
-            throw new IllegalArgumentException(hostPort + " doesn't have a port after colon.");
-        }
-        //do not include
-        String port = hostPort.substring(indexOfClosingBracket + 2);
-        return new String[] { host, port };
-    }
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/SyncRequestProcessor.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/SyncRequestProcessor.java
deleted file mode 100644
index cf7f4c44015..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/SyncRequestProcessor.java
+++ /dev/null
@@ -1,353 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.zookeeper.server;
-
-import java.io.Flushable;
-import java.io.IOException;
-import java.util.ArrayDeque;
-import java.util.Objects;
-import java.util.Queue;
-import java.util.concurrent.BlockingQueue;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.LinkedBlockingQueue;
-import java.util.concurrent.Semaphore;
-import java.util.concurrent.ThreadLocalRandom;
-import java.util.concurrent.TimeUnit;
-import org.apache.zookeeper.common.Time;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-/**
- * This RequestProcessor logs requests to disk. It batches the requests to do
- * the io efficiently. The request is not passed to the next RequestProcessor
- * until its log has been synced to disk.
- *
- * SyncRequestProcessor is used in 3 different cases
- * 1. Leader - Sync request to disk and forward it to AckRequestProcessor which
- *             send ack back to itself.
- * 2. Follower - Sync request to disk and forward request to
- *             SendAckRequestProcessor which send the packets to leader.
- *             SendAckRequestProcessor is flushable which allow us to force
- *             push packets to leader.
- * 3. Observer - Sync committed request to disk (received as INFORM packet).
- *             It never send ack back to the leader, so the nextProcessor will
- *             be null. This change the semantic of txnlog on the observer
- *             since it only contains committed txns.
- */
-public class SyncRequestProcessor extends ZooKeeperCriticalThread implements RequestProcessor {
-
-    private static final Logger LOG = LoggerFactory.getLogger(SyncRequestProcessor.class);
-
-    private static final Request REQUEST_OF_DEATH = Request.requestOfDeath;
-
-    private static class FlushRequest extends Request {
-        private final CountDownLatch latch = new CountDownLatch(1);
-        public FlushRequest() {
-            super(null, 0, 0, 0, null, null);
-        }
-    }
-
-    private static final Request TURN_FORWARDING_DELAY_ON_REQUEST = new Request(null, 0, 0, 0, null, null);
-    private static final Request TURN_FORWARDING_DELAY_OFF_REQUEST = new Request(null, 0, 0, 0, null, null);
-
-    private static class DelayingProcessor implements RequestProcessor, Flushable {
-        private final RequestProcessor next;
-        private Queue<Request> delayed = null;
-        private DelayingProcessor(RequestProcessor next) {
-            this.next = next;
-        }
-        @Override
-        public void flush() throws IOException {
-            if (delayed == null && next instanceof Flushable) {
-                ((Flushable) next).flush();
-            }
-        }
-        @Override
-        public void processRequest(Request request) throws RequestProcessorException {
-            if (delayed == null) {
-                next.processRequest(request);
-            } else {
-                delayed.add(request);
-            }
-        }
-        @Override
-        public void shutdown() {
-            next.shutdown();
-        }
-        private void startDelaying() {
-            if (delayed == null) {
-                delayed = new ArrayDeque<>();
-            }
-        }
-        private void flushAndStopDelaying() throws RequestProcessorException {
-            if (delayed != null) {
-                for (Request request : delayed) {
-                    next.processRequest(request);
-                }
-                delayed = null;
-            }
-        }
-    }
-
-    /** The number of log entries to log before starting a snapshot */
-    private static int snapCount = ZooKeeperServer.getSnapCount();
-
-    /**
-     * The total size of log entries before starting a snapshot
-     */
-    private static long snapSizeInBytes = ZooKeeperServer.getSnapSizeInBytes();
-
-    /**
-     * Random numbers used to vary snapshot timing
-     */
-    private int randRoll;
-    private long randSize;
-
-    private final BlockingQueue<Request> queuedRequests = new LinkedBlockingQueue<>();
-
-    private final Semaphore snapThreadMutex = new Semaphore(1);
-
-    private final ZooKeeperServer zks;
-
-    private final DelayingProcessor nextProcessor;
-
-    /**
-     * Transactions that have been written and are waiting to be flushed to
-     * disk. Basically this is the list of SyncItems whose callbacks will be
-     * invoked after flush returns successfully.
-     */
-    private final Queue<Request> toFlush;
-    private long lastFlushTime;
-
-    public SyncRequestProcessor(ZooKeeperServer zks, RequestProcessor nextProcessor) {
-        super("SyncThread:" + zks.getServerId(), zks.getZooKeeperServerListener());
-        this.zks = zks;
-        this.nextProcessor = nextProcessor == null ? null : new DelayingProcessor(nextProcessor);
-        this.toFlush = new ArrayDeque<>(zks.getMaxBatchSize());
-    }
-
-    /**
-     * used by tests to check for changing
-     * snapcounts
-     * @param count
-     */
-    public static void setSnapCount(int count) {
-        snapCount = count;
-    }
-
-    /**
-     * used by tests to get the snapcount
-     * @return the snapcount
-     */
-    public static int getSnapCount() {
-        return snapCount;
-    }
-
-    private long getRemainingDelay() {
-        long flushDelay = zks.getFlushDelay();
-        long duration = Time.currentElapsedTime() - lastFlushTime;
-        if (duration < flushDelay) {
-            return flushDelay - duration;
-        }
-        return 0;
-    }
-
-    /** If both flushDelay and maxMaxBatchSize are set (bigger than 0), flush
-     * whenever either condition is hit. If only one or the other is
-     * set, flush only when the relevant condition is hit.
-     */
-    private boolean shouldFlush() {
-        long flushDelay = zks.getFlushDelay();
-        long maxBatchSize = zks.getMaxBatchSize();
-        if ((flushDelay > 0) && (getRemainingDelay() == 0)) {
-            return true;
-        }
-        return (maxBatchSize > 0) && (toFlush.size() >= maxBatchSize);
-    }
-
-    /**
-     * used by tests to check for changing
-     * snapcounts
-     * @param size
-     */
-    public static void setSnapSizeInBytes(long size) {
-        snapSizeInBytes = size;
-    }
-
-    private boolean shouldSnapshot() {
-        int logCount = zks.getZKDatabase().getTxnCount();
-        long logSize = zks.getZKDatabase().getTxnSize();
-        return (logCount > (snapCount / 2 + randRoll))
-               || (snapSizeInBytes > 0 && logSize > (snapSizeInBytes / 2 + randSize));
-    }
-
-    private void resetSnapshotStats() {
-        randRoll = ThreadLocalRandom.current().nextInt(snapCount / 2);
-        randSize = Math.abs(ThreadLocalRandom.current().nextLong() % (snapSizeInBytes / 2));
-    }
-
-    @Override
-    public void run() {
-        try {
-            // we do this in an attempt to ensure that not all of the servers
-            // in the ensemble take a snapshot at the same time
-            resetSnapshotStats();
-            lastFlushTime = Time.currentElapsedTime();
-            while (true) {
-                ServerMetrics.getMetrics().SYNC_PROCESSOR_QUEUE_SIZE.add(queuedRequests.size());
-
-                long pollTime = Math.min(zks.getMaxWriteQueuePollTime(), getRemainingDelay());
-                Request si = queuedRequests.poll(pollTime, TimeUnit.MILLISECONDS);
-                if (si == null) {
-                    /* We timed out looking for more writes to batch, go ahead and flush immediately */
-                    flush();
-                    si = queuedRequests.take();
-                }
-
-                if (si == REQUEST_OF_DEATH) {
-                    break;
-                }
-
-                if (si == TURN_FORWARDING_DELAY_ON_REQUEST) {
-                    nextProcessor.startDelaying();
-                    continue;
-                }
-                if (si == TURN_FORWARDING_DELAY_OFF_REQUEST) {
-                    nextProcessor.flushAndStopDelaying();
-                    continue;
-                }
-
-                if (si instanceof FlushRequest) {
-                    flush();
-                    ((FlushRequest) si).latch.countDown();
-                    continue;
-                }
-
-                long startProcessTime = Time.currentElapsedTime();
-                ServerMetrics.getMetrics().SYNC_PROCESSOR_QUEUE_TIME.add(startProcessTime - si.syncQueueStartTime);
-
-                // track the number of records written to the log
-                if (!si.isThrottled() && zks.getZKDatabase().append(si)) {
-                    if (shouldSnapshot()) {
-                        resetSnapshotStats();
-                        // roll the log
-                        zks.getZKDatabase().rollLog();
-                        // take a snapshot
-                        if (!snapThreadMutex.tryAcquire()) {
-                            LOG.warn("Too busy to snap, skipping");
-                        } else {
-                            new ZooKeeperThread("Snapshot Thread") {
-                                public void run() {
-                                    try {
-                                        zks.takeSnapshot();
-                                    } catch (Exception e) {
-                                        LOG.warn("Unexpected exception", e);
-                                    } finally {
-                                        snapThreadMutex.release();
-                                    }
-                                }
-                            }.start();
-                        }
-                    }
-                } else if (toFlush.isEmpty()) {
-                    // optimization for read heavy workloads
-                    // iff this is a read or a throttled request(which doesn't need to be written to the disk),
-                    // and there are no pending flushes (writes), then just pass this to the next processor
-                    if (nextProcessor != null) {
-                        nextProcessor.processRequest(si);
-                        nextProcessor.flush();
-                    }
-                    continue;
-                }
-                toFlush.add(si);
-                if (shouldFlush()) {
-                    flush();
-                }
-                ServerMetrics.getMetrics().SYNC_PROCESS_TIME.add(Time.currentElapsedTime() - startProcessTime);
-            }
-        } catch (Throwable t) {
-            handleException(this.getName(), t);
-        }
-        LOG.info("SyncRequestProcessor exited!");
-    }
-
-    /** Flushes all pending writes, and waits for this to complete. */
-    public void syncFlush() throws InterruptedException {
-        FlushRequest marker = new FlushRequest();
-        queuedRequests.add(marker);
-        marker.latch.await();
-    }
-
-    public void setDelayForwarding(boolean delayForwarding) {
-        queuedRequests.add(delayForwarding ? TURN_FORWARDING_DELAY_ON_REQUEST : TURN_FORWARDING_DELAY_OFF_REQUEST);
-    }
-
-    private void flush() throws IOException, RequestProcessorException {
-        if (this.toFlush.isEmpty()) {
-            return;
-        }
-
-        ServerMetrics.getMetrics().BATCH_SIZE.add(toFlush.size());
-
-        long flushStartTime = Time.currentElapsedTime();
-        zks.getZKDatabase().commit();
-        ServerMetrics.getMetrics().SYNC_PROCESSOR_FLUSH_TIME.add(Time.currentElapsedTime() - flushStartTime);
-
-        if (this.nextProcessor == null) {
-            this.toFlush.clear();
-        } else {
-            while (!this.toFlush.isEmpty()) {
-                final Request i = this.toFlush.remove();
-                long latency = Time.currentElapsedTime() - i.syncQueueStartTime;
-                ServerMetrics.getMetrics().SYNC_PROCESSOR_QUEUE_AND_FLUSH_TIME.add(latency);
-                this.nextProcessor.processRequest(i);
-            }
-            nextProcessor.flush();
-        }
-        lastFlushTime = Time.currentElapsedTime();
-    }
-
-    public void shutdown() {
-        LOG.info("Shutting down");
-        queuedRequests.add(REQUEST_OF_DEATH);
-        try {
-            this.join();
-            this.flush();
-        } catch (InterruptedException e) {
-            LOG.warn("Interrupted while wating for {} to finish", this);
-            Thread.currentThread().interrupt();
-        } catch (IOException e) {
-            LOG.warn("Got IO exception during shutdown");
-        } catch (RequestProcessorException e) {
-            LOG.warn("Got request processor exception during shutdown");
-        }
-        if (nextProcessor != null) {
-            nextProcessor.shutdown();
-        }
-    }
-
-    public void processRequest(final Request request) {
-        Objects.requireNonNull(request, "Request cannot be null");
-
-        request.syncQueueStartTime = Time.currentElapsedTime();
-        queuedRequests.add(request);
-        ServerMetrics.getMetrics().SYNC_PROCESSOR_QUEUED.add(1);
-    }
-
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/VespaNettyServerCnxnFactory.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/VespaNettyServerCnxnFactory.java
deleted file mode 100644
index 114d2987fe2..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/VespaNettyServerCnxnFactory.java
+++ /dev/null
@@ -1,37 +0,0 @@
-// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-package org.apache.zookeeper.server;
-
-import com.yahoo.vespa.zookeeper.Configurator;
-
-import java.io.IOException;
-import java.net.InetSocketAddress;
-import java.util.logging.Logger;
-
-/**
- * Overrides secure setting with value from {@link Configurator}.
- * Workaround for incorrect handling of clientSecurePort in combination with ZooKeeper Dynamic Reconfiguration in 3.6.2
- * See https://issues.apache.org/jira/browse/ZOOKEEPER-3577.
- *
- * Using package {@link org.apache.zookeeper.server} as {@link NettyServerCnxnFactory#NettyServerCnxnFactory()} is package-private.
- *
- * @author bjorncs
- */
-public class VespaNettyServerCnxnFactory extends NettyServerCnxnFactory {
-
-    private static final Logger log = Logger.getLogger(VespaNettyServerCnxnFactory.class.getName());
-
-    private final boolean isSecure;
-
-    public VespaNettyServerCnxnFactory() {
-        super();
-        this.isSecure = Configurator.VespaNettyServerCnxnFactory_isSecure;
-        boolean portUnificationEnabled = Boolean.getBoolean(NettyServerCnxnFactory.PORT_UNIFICATION_KEY);
-        log.info(String.format("For %h: isSecure=%b, portUnification=%b", this, isSecure, portUnificationEnabled));
-    }
-
-    @Override
-    public void configure(InetSocketAddress addr, int maxClientCnxns, int backlog, boolean secure) throws IOException {
-        log.info(String.format("For %h: configured() invoked with parameter 'secure'=%b, overridden to %b", this, secure, isSecure));
-        super.configure(addr, maxClientCnxns, backlog, isSecure);
-    }
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/ZooKeeperServer.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/ZooKeeperServer.java
deleted file mode 100644
index 00af31b46d4..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/ZooKeeperServer.java
+++ /dev/null
@@ -1,2412 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.zookeeper.server;
-
-import java.io.BufferedInputStream;
-import java.io.ByteArrayOutputStream;
-import java.io.File;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.PrintWriter;
-import java.nio.ByteBuffer;
-import java.util.ArrayDeque;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Deque;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Properties;
-import java.util.Random;
-import java.util.Set;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.atomic.AtomicInteger;
-import java.util.concurrent.atomic.AtomicLong;
-import java.util.function.BiConsumer;
-import java.util.zip.Adler32;
-import java.util.zip.CheckedInputStream;
-import javax.security.sasl.SaslException;
-import org.apache.jute.BinaryInputArchive;
-import org.apache.jute.BinaryOutputArchive;
-import org.apache.jute.InputArchive;
-import org.apache.jute.Record;
-import org.apache.zookeeper.Environment;
-import org.apache.zookeeper.KeeperException;
-import org.apache.zookeeper.KeeperException.Code;
-import org.apache.zookeeper.KeeperException.SessionExpiredException;
-import org.apache.zookeeper.Quotas;
-import org.apache.zookeeper.StatsTrack;
-import org.apache.zookeeper.Version;
-import org.apache.zookeeper.ZooDefs;
-import org.apache.zookeeper.ZooDefs.OpCode;
-import org.apache.zookeeper.ZookeeperBanner;
-import org.apache.zookeeper.common.PathUtils;
-import org.apache.zookeeper.common.StringUtils;
-import org.apache.zookeeper.common.Time;
-import org.apache.zookeeper.data.ACL;
-import org.apache.zookeeper.data.Id;
-import org.apache.zookeeper.data.StatPersisted;
-import org.apache.zookeeper.jmx.MBeanRegistry;
-import org.apache.zookeeper.metrics.MetricsContext;
-import org.apache.zookeeper.proto.AuthPacket;
-import org.apache.zookeeper.proto.ConnectRequest;
-import org.apache.zookeeper.proto.ConnectResponse;
-import org.apache.zookeeper.proto.CreateRequest;
-import org.apache.zookeeper.proto.DeleteRequest;
-import org.apache.zookeeper.proto.GetSASLRequest;
-import org.apache.zookeeper.proto.ReplyHeader;
-import org.apache.zookeeper.proto.RequestHeader;
-import org.apache.zookeeper.proto.SetACLRequest;
-import org.apache.zookeeper.proto.SetDataRequest;
-import org.apache.zookeeper.proto.SetSASLResponse;
-import org.apache.zookeeper.server.DataTree.ProcessTxnResult;
-import org.apache.zookeeper.server.RequestProcessor.RequestProcessorException;
-import org.apache.zookeeper.server.ServerCnxn.CloseRequestException;
-import org.apache.zookeeper.server.SessionTracker.Session;
-import org.apache.zookeeper.server.SessionTracker.SessionExpirer;
-import org.apache.zookeeper.server.auth.ProviderRegistry;
-import org.apache.zookeeper.server.auth.ServerAuthenticationProvider;
-import org.apache.zookeeper.server.persistence.FileTxnSnapLog;
-import org.apache.zookeeper.server.quorum.QuorumPeerConfig;
-import org.apache.zookeeper.server.quorum.ReadOnlyZooKeeperServer;
-import org.apache.zookeeper.server.util.JvmPauseMonitor;
-import org.apache.zookeeper.server.util.OSMXBean;
-import org.apache.zookeeper.server.util.QuotaMetricsUtils;
-import org.apache.zookeeper.server.util.RequestPathMetricsCollector;
-import org.apache.zookeeper.txn.CreateSessionTxn;
-import org.apache.zookeeper.txn.TxnDigest;
-import org.apache.zookeeper.txn.TxnHeader;
-import org.apache.zookeeper.util.ServiceUtils;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-/**
- * This class implements a simple standalone ZooKeeperServer. It sets up the
- * following chain of RequestProcessors to process requests:
- * PrepRequestProcessor -&gt; SyncRequestProcessor -&gt; FinalRequestProcessor
- */
-public class ZooKeeperServer implements SessionExpirer, ServerStats.Provider {
-
-    protected static final Logger LOG;
-    private static final RateLogger RATE_LOGGER;
-
-    public static final String GLOBAL_OUTSTANDING_LIMIT = "zookeeper.globalOutstandingLimit";
-
-    public static final String ENABLE_EAGER_ACL_CHECK = "zookeeper.enableEagerACLCheck";
-    public static final String SKIP_ACL = "zookeeper.skipACL";
-    public static final String ENFORCE_QUOTA = "zookeeper.enforceQuota";
-
-    // When enabled, will check ACL constraints appertained to the requests first,
-    // before sending the requests to the quorum.
-    static boolean enableEagerACLCheck;
-
-    static final boolean skipACL;
-
-    public static final boolean enforceQuota;
-
-    public static final String SASL_SUPER_USER = "zookeeper.superUser";
-
-    public static final String ALLOW_SASL_FAILED_CLIENTS = "zookeeper.allowSaslFailedClients";
-    public static final String ZOOKEEPER_DIGEST_ENABLED = "zookeeper.digest.enabled";
-    private static boolean digestEnabled;
-
-    public static final String ZOOKEEPER_SERIALIZE_LAST_PROCESSED_ZXID_ENABLED = "zookeeper.serializeLastProcessedZxid.enabled";
-    private static boolean serializeLastProcessedZxidEnabled;
-
-    // Add a enable/disable option for now, we should remove this one when
-    // this feature is confirmed to be stable
-    public static final String CLOSE_SESSION_TXN_ENABLED = "zookeeper.closeSessionTxn.enabled";
-    private static boolean closeSessionTxnEnabled = true;
-    private volatile CountDownLatch restoreLatch;
-
-    static {
-        LOG = LoggerFactory.getLogger(ZooKeeperServer.class);
-
-        RATE_LOGGER = new RateLogger(LOG);
-
-        ZookeeperBanner.printBanner(LOG);
-
-        Environment.logEnv("Server environment:", LOG);
-
-        enableEagerACLCheck = Boolean.getBoolean(ENABLE_EAGER_ACL_CHECK);
-        LOG.info("{} = {}", ENABLE_EAGER_ACL_CHECK, enableEagerACLCheck);
-
-        skipACL = System.getProperty(SKIP_ACL, "no").equals("yes");
-        if (skipACL) {
-            LOG.info("{}==\"yes\", ACL checks will be skipped", SKIP_ACL);
-        }
-
-        enforceQuota = Boolean.parseBoolean(System.getProperty(ENFORCE_QUOTA, "false"));
-        if (enforceQuota) {
-            LOG.info("{} = {}, Quota Enforce enables", ENFORCE_QUOTA, enforceQuota);
-        }
-
-        digestEnabled = Boolean.parseBoolean(System.getProperty(ZOOKEEPER_DIGEST_ENABLED, "true"));
-        LOG.info("{} = {}", ZOOKEEPER_DIGEST_ENABLED, digestEnabled);
-
-        closeSessionTxnEnabled = Boolean.parseBoolean(
-                System.getProperty(CLOSE_SESSION_TXN_ENABLED, "true"));
-        LOG.info("{} = {}", CLOSE_SESSION_TXN_ENABLED, closeSessionTxnEnabled);
-
-        setSerializeLastProcessedZxidEnabled(Boolean.parseBoolean(
-                System.getProperty(ZOOKEEPER_SERIALIZE_LAST_PROCESSED_ZXID_ENABLED, "true")));
-    }
-
-    // @VisibleForTesting
-    public static boolean isEnableEagerACLCheck() {
-        return enableEagerACLCheck;
-    }
-
-    // @VisibleForTesting
-    public static void setEnableEagerACLCheck(boolean enabled) {
-        ZooKeeperServer.enableEagerACLCheck = enabled;
-        LOG.info("Update {} to {}", ENABLE_EAGER_ACL_CHECK, enabled);
-    }
-
-    public static boolean isCloseSessionTxnEnabled() {
-        return closeSessionTxnEnabled;
-    }
-
-    public static void setCloseSessionTxnEnabled(boolean enabled) {
-        ZooKeeperServer.closeSessionTxnEnabled = enabled;
-        LOG.info("Update {} to {}", CLOSE_SESSION_TXN_ENABLED,
-                ZooKeeperServer.closeSessionTxnEnabled);
-    }
-
-    protected ZooKeeperServerBean jmxServerBean;
-    protected DataTreeBean jmxDataTreeBean;
-
-    public static final int DEFAULT_TICK_TIME = 3000;
-    protected int tickTime = DEFAULT_TICK_TIME;
-    public static final int DEFAULT_THROTTLED_OP_WAIT_TIME = 0; // disabled
-    protected static volatile int throttledOpWaitTime =
-        Integer.getInteger("zookeeper.throttled_op_wait_time", DEFAULT_THROTTLED_OP_WAIT_TIME);
-    /** value of -1 indicates unset, use default */
-    protected int minSessionTimeout = -1;
-    /** value of -1 indicates unset, use default */
-    protected int maxSessionTimeout = -1;
-    /** Socket listen backlog. Value of -1 indicates unset */
-    protected int listenBacklog = -1;
-    protected SessionTracker sessionTracker;
-    private FileTxnSnapLog txnLogFactory = null;
-    private ZKDatabase zkDb;
-    private ResponseCache readResponseCache;
-    private ResponseCache getChildrenResponseCache;
-    private final AtomicLong hzxid = new AtomicLong(0);
-    public static final Exception ok = new Exception("No prob");
-    protected RequestProcessor firstProcessor;
-    protected JvmPauseMonitor jvmPauseMonitor;
-    protected volatile State state = State.INITIAL;
-    private boolean isResponseCachingEnabled = true;
-    /* contains the configuration file content read at startup */
-    protected String initialConfig;
-    protected boolean reconfigEnabled;
-    private final RequestPathMetricsCollector requestPathMetricsCollector;
-    private static final int DEFAULT_SNAP_COUNT = 100000;
-    private static final int DEFAULT_GLOBAL_OUTSTANDING_LIMIT = 1000;
-
-    private boolean localSessionEnabled = false;
-    protected enum State {
-        INITIAL,
-        RUNNING,
-        SHUTDOWN,
-        ERROR
-    }
-
-    /**
-     * This is the secret that we use to generate passwords. For the moment,
-     * it's more of a checksum that's used in reconnection, which carries no
-     * security weight, and is treated internally as if it carries no
-     * security weight.
-     */
-    private static final long superSecret = 0XB3415C00L;
-
-    private final AtomicInteger requestsInProcess = new AtomicInteger(0);
-    final Deque<ChangeRecord> outstandingChanges = new ArrayDeque<>();
-    // this data structure must be accessed under the outstandingChanges lock
-    final Map<String, ChangeRecord> outstandingChangesForPath = new HashMap<>();
-
-    protected ServerCnxnFactory serverCnxnFactory;
-    protected ServerCnxnFactory secureServerCnxnFactory;
-
-    private final ServerStats serverStats;
-    private final ZooKeeperServerListener listener;
-    private ZooKeeperServerShutdownHandler zkShutdownHandler;
-    private volatile int createSessionTrackerServerId = 1;
-
-    private static final String FLUSH_DELAY = "zookeeper.flushDelay";
-    private static volatile long flushDelay;
-    private static final String MAX_WRITE_QUEUE_POLL_SIZE = "zookeeper.maxWriteQueuePollTime";
-    private static volatile long maxWriteQueuePollTime;
-    private static final String MAX_BATCH_SIZE = "zookeeper.maxBatchSize";
-    private static volatile int maxBatchSize;
-
-    /**
-     * Starting size of read and write ByteArroyOuputBuffers. Default is 32 bytes.
-     * Flag not used for small transfers like connectResponses.
-     */
-    public static final String INT_BUFFER_STARTING_SIZE_BYTES = "zookeeper.intBufferStartingSizeBytes";
-    public static final int DEFAULT_STARTING_BUFFER_SIZE = 1024;
-    public static final int intBufferStartingSizeBytes;
-
-    public static final String GET_DATA_RESPONSE_CACHE_SIZE = "zookeeper.maxResponseCacheSize";
-    public static final String GET_CHILDREN_RESPONSE_CACHE_SIZE = "zookeeper.maxGetChildrenResponseCacheSize";
-
-    static {
-        long configuredFlushDelay = Long.getLong(FLUSH_DELAY, 0);
-        setFlushDelay(configuredFlushDelay);
-        setMaxWriteQueuePollTime(Long.getLong(MAX_WRITE_QUEUE_POLL_SIZE, configuredFlushDelay / 3));
-        setMaxBatchSize(Integer.getInteger(MAX_BATCH_SIZE, 1000));
-
-        intBufferStartingSizeBytes = Integer.getInteger(INT_BUFFER_STARTING_SIZE_BYTES, DEFAULT_STARTING_BUFFER_SIZE);
-
-        if (intBufferStartingSizeBytes < 32) {
-            String msg = "Buffer starting size (" + intBufferStartingSizeBytes + ") must be greater than or equal to 32. "
-                         + "Configure with \"-Dzookeeper.intBufferStartingSizeBytes=<size>\" ";
-            LOG.error(msg);
-            throw new IllegalArgumentException(msg);
-        }
-
-        LOG.info("{} = {}", INT_BUFFER_STARTING_SIZE_BYTES, intBufferStartingSizeBytes);
-    }
-
-    // Connection throttling
-    private final BlueThrottle connThrottle = new BlueThrottle();
-
-    private RequestThrottler requestThrottler;
-    public static final String SNAP_COUNT = "zookeeper.snapCount";
-
-    /**
-     * This setting sets a limit on the total number of large requests that
-     * can be inflight and is designed to prevent ZooKeeper from accepting
-     * too many large requests such that the JVM runs out of usable heap and
-     * ultimately crashes.
-     *
-     * The limit is enforced by the {@link #checkRequestSizeWhenReceivingMessage(int)}
-     * method which is called by the connection layer ({@link NIOServerCnxn},
-     * {@link NettyServerCnxn}) before allocating a byte buffer and pulling
-     * data off the TCP socket. The limit is then checked again by the
-     * ZooKeeper server in {@link #processPacket(ServerCnxn, RequestHeader, RequestRecord)} which
-     * also atomically updates {@link #currentLargeRequestBytes}. The request is
-     * then marked as a large request, with the request size stored in the Request
-     * object so that it can later be decremented from {@link #currentLargeRequestBytes}.
-     *
-     * When a request is completed or dropped, the relevant code path calls the
-     * {@link #requestFinished(Request)} method which performs the decrement if
-     * needed.
-     */
-    private volatile int largeRequestMaxBytes = 100 * 1024 * 1024;
-
-    /**
-     * The size threshold after which a request is considered a large request
-     * and is checked against the large request byte limit.
-     */
-    private volatile int largeRequestThreshold = -1;
-
-    private final AtomicInteger currentLargeRequestBytes = new AtomicInteger(0);
-
-    private final AuthenticationHelper authHelper = new AuthenticationHelper();
-
-    void removeCnxn(ServerCnxn cnxn) {
-        zkDb.removeCnxn(cnxn);
-    }
-
-    /**
-     * Creates a ZooKeeperServer instance. Nothing is setup, use the setX
-     * methods to prepare the instance (eg datadir, datalogdir, ticktime,
-     * builder, etc...)
-     *
-     */
-    public ZooKeeperServer() {
-        listener = new ZooKeeperServerListenerImpl(this);
-        serverStats = new ServerStats(this);
-        this.requestPathMetricsCollector = new RequestPathMetricsCollector();
-    }
-
-    /**
-     * Keeping this constructor for backward compatibility
-     */
-    public ZooKeeperServer(FileTxnSnapLog txnLogFactory, int tickTime, int minSessionTimeout, int maxSessionTimeout, int clientPortListenBacklog, ZKDatabase zkDb, String initialConfig) {
-        this(txnLogFactory, tickTime, minSessionTimeout, maxSessionTimeout, clientPortListenBacklog, zkDb, initialConfig, QuorumPeerConfig.isReconfigEnabled());
-    }
-
-    /**
-     *  * Creates a ZooKeeperServer instance. It sets everything up, but doesn't
-     * actually start listening for clients until run() is invoked.
-     *
-     */
-    public ZooKeeperServer(FileTxnSnapLog txnLogFactory, int tickTime, int minSessionTimeout, int maxSessionTimeout, int clientPortListenBacklog, ZKDatabase zkDb, String initialConfig, boolean reconfigEnabled) {
-        serverStats = new ServerStats(this);
-        this.txnLogFactory = txnLogFactory;
-        this.txnLogFactory.setServerStats(this.serverStats);
-        this.zkDb = zkDb;
-        this.tickTime = tickTime;
-        setMinSessionTimeout(minSessionTimeout);
-        setMaxSessionTimeout(maxSessionTimeout);
-        this.listenBacklog = clientPortListenBacklog;
-        this.reconfigEnabled = reconfigEnabled;
-
-        listener = new ZooKeeperServerListenerImpl(this);
-
-        readResponseCache = new ResponseCache(Integer.getInteger(
-            GET_DATA_RESPONSE_CACHE_SIZE,
-            ResponseCache.DEFAULT_RESPONSE_CACHE_SIZE), "getData");
-
-        getChildrenResponseCache = new ResponseCache(Integer.getInteger(
-            GET_CHILDREN_RESPONSE_CACHE_SIZE,
-            ResponseCache.DEFAULT_RESPONSE_CACHE_SIZE), "getChildren");
-
-        this.initialConfig = initialConfig;
-
-        this.requestPathMetricsCollector = new RequestPathMetricsCollector();
-
-        this.initLargeRequestThrottlingSettings();
-
-        LOG.info(
-            "Created server with"
-                + " tickTime {} ms"
-                + " minSessionTimeout {} ms"
-                + " maxSessionTimeout {} ms"
-                + " clientPortListenBacklog {}"
-                + " dataLogdir {}"
-                + " snapdir {}",
-            tickTime,
-            getMinSessionTimeout(),
-            getMaxSessionTimeout(),
-            getClientPortListenBacklog(),
-            txnLogFactory.getDataLogDir(),
-            txnLogFactory.getSnapDir());
-    }
-
-    public String getInitialConfig() {
-        return initialConfig;
-    }
-
-    /**
-     * Adds JvmPauseMonitor and calls
-     * {@link #ZooKeeperServer(FileTxnSnapLog, int, int, int, int, ZKDatabase, String)}
-     *
-     */
-    public ZooKeeperServer(JvmPauseMonitor jvmPauseMonitor, FileTxnSnapLog txnLogFactory, int tickTime, int minSessionTimeout, int maxSessionTimeout, int clientPortListenBacklog, ZKDatabase zkDb, String initialConfig) {
-        this(txnLogFactory, tickTime, minSessionTimeout, maxSessionTimeout, clientPortListenBacklog, zkDb, initialConfig, QuorumPeerConfig.isReconfigEnabled());
-        this.jvmPauseMonitor = jvmPauseMonitor;
-        if (jvmPauseMonitor != null) {
-            LOG.info("Added JvmPauseMonitor to server");
-        }
-    }
-
-    /**
-     * creates a zookeeperserver instance.
-     * @param txnLogFactory the file transaction snapshot logging class
-     * @param tickTime the ticktime for the server
-     */
-    public ZooKeeperServer(FileTxnSnapLog txnLogFactory, int tickTime, String initialConfig) {
-        this(txnLogFactory, tickTime, -1, -1, -1, new ZKDatabase(txnLogFactory), initialConfig, QuorumPeerConfig.isReconfigEnabled());
-    }
-
-    public ServerStats serverStats() {
-        return serverStats;
-    }
-
-    public RequestPathMetricsCollector getRequestPathMetricsCollector() {
-        return requestPathMetricsCollector;
-    }
-
-    public BlueThrottle connThrottle() {
-        return connThrottle;
-    }
-
-    public void dumpConf(PrintWriter pwriter) {
-        pwriter.print("clientPort=");
-        pwriter.println(getClientPort());
-        pwriter.print("secureClientPort=");
-        pwriter.println(getSecureClientPort());
-        pwriter.print("dataDir=");
-        pwriter.println(zkDb.snapLog.getSnapDir().getAbsolutePath());
-        pwriter.print("dataDirSize=");
-        pwriter.println(getDataDirSize());
-        pwriter.print("dataLogDir=");
-        pwriter.println(zkDb.snapLog.getDataLogDir().getAbsolutePath());
-        pwriter.print("dataLogSize=");
-        pwriter.println(getLogDirSize());
-        pwriter.print("tickTime=");
-        pwriter.println(getTickTime());
-        pwriter.print("maxClientCnxns=");
-        pwriter.println(getMaxClientCnxnsPerHost());
-        pwriter.print("minSessionTimeout=");
-        pwriter.println(getMinSessionTimeout());
-        pwriter.print("maxSessionTimeout=");
-        pwriter.println(getMaxSessionTimeout());
-        pwriter.print("clientPortListenBacklog=");
-        pwriter.println(getClientPortListenBacklog());
-
-        pwriter.print("serverId=");
-        pwriter.println(getServerId());
-    }
-
-    public ZooKeeperServerConf getConf() {
-        return new ZooKeeperServerConf(
-            getClientPort(),
-            zkDb.snapLog.getSnapDir().getAbsolutePath(),
-            zkDb.snapLog.getDataLogDir().getAbsolutePath(),
-            getTickTime(),
-            getMaxClientCnxnsPerHost(),
-            getMinSessionTimeout(),
-            getMaxSessionTimeout(),
-            getServerId(),
-            getClientPortListenBacklog());
-    }
-
-    /**
-     * This constructor is for backward compatibility with the existing unit
-     * test code.
-     * It defaults to FileLogProvider persistence provider.
-     */
-    public ZooKeeperServer(File snapDir, File logDir, int tickTime) throws IOException {
-        this(new FileTxnSnapLog(snapDir, logDir), tickTime, "");
-    }
-
-    /**
-     * Default constructor, relies on the config for its argument values
-     *
-     * @throws IOException
-     */
-    public ZooKeeperServer(FileTxnSnapLog txnLogFactory) throws IOException {
-        this(txnLogFactory, DEFAULT_TICK_TIME, -1, -1, -1, new ZKDatabase(txnLogFactory), "", QuorumPeerConfig.isReconfigEnabled());
-    }
-
-    /**
-     * get the zookeeper database for this server
-     * @return the zookeeper database for this server
-     */
-    public ZKDatabase getZKDatabase() {
-        return this.zkDb;
-    }
-
-    /**
-     * set the zkdatabase for this zookeeper server
-     * @param zkDb
-     */
-    public void setZKDatabase(ZKDatabase zkDb) {
-        this.zkDb = zkDb;
-    }
-
-    /**
-     *  Restore sessions and data
-     */
-    public void loadData() throws IOException, InterruptedException {
-        /*
-         * When a new leader starts executing Leader#lead, it
-         * invokes this method. The database, however, has been
-         * initialized before running leader election so that
-         * the server could pick its zxid for its initial vote.
-         * It does it by invoking QuorumPeer#getLastLoggedZxid.
-         * Consequently, we don't need to initialize it once more
-         * and avoid the penalty of loading it a second time. Not
-         * reloading it is particularly important for applications
-         * that host a large database.
-         *
-         * The following if block checks whether the database has
-         * been initialized or not. Note that this method is
-         * invoked by at least one other method:
-         * ZooKeeperServer#startdata.
-         *
-         * See ZOOKEEPER-1642 for more detail.
-         */
-        if (zkDb.isInitialized()) {
-            setZxid(zkDb.getDataTreeLastProcessedZxid());
-        } else {
-            setZxid(zkDb.loadDataBase());
-        }
-
-        // Clean up dead sessions
-        zkDb.getSessions().stream()
-                        .filter(session -> zkDb.getSessionWithTimeOuts().get(session) == null)
-                        .forEach(session -> killSession(session, zkDb.getDataTreeLastProcessedZxid()));
-
-        // Make a clean snapshot
-        takeSnapshot();
-    }
-
-    public File takeSnapshot() throws IOException {
-        return takeSnapshot(false);
-    }
-
-    public File takeSnapshot(boolean syncSnap) throws IOException {
-        return takeSnapshot(syncSnap, true, false);
-    }
-
-    /**
-     * Takes a snapshot on the server.
-     *
-     * @param syncSnap syncSnap sync the snapshot immediately after write
-     * @param isSevere if true system exist, otherwise throw IOException
-     * @param fastForwardFromEdits whether fast forward database to the latest recorded transactions
-     *
-     * @return file snapshot file object
-     * @throws IOException
-     */
-    public synchronized File takeSnapshot(boolean syncSnap, boolean isSevere, boolean fastForwardFromEdits) throws IOException {
-        long start = Time.currentElapsedTime();
-        File snapFile = null;
-        try {
-            if (fastForwardFromEdits) {
-                zkDb.fastForwardDataBase();
-            }
-            snapFile = txnLogFactory.save(zkDb.getDataTree(), zkDb.getSessionWithTimeOuts(), syncSnap);
-        } catch (IOException e) {
-            if (isSevere) {
-                LOG.error("Severe unrecoverable error, exiting", e);
-                // This is a severe error that we cannot recover from,
-                // so we need to exit
-                ServiceUtils.requestSystemExit(ExitCode.TXNLOG_ERROR_TAKING_SNAPSHOT.getValue());
-            } else {
-                throw e;
-            }
-        }
-        long elapsed = Time.currentElapsedTime() - start;
-        LOG.info("Snapshot taken in {} ms", elapsed);
-        ServerMetrics.getMetrics().SNAPSHOT_TIME.add(elapsed);
-        return snapFile;
-    }
-
-    /**
-     * Restores database from a snapshot. It is used by the restore admin server command.
-     *
-     * @param inputStream input stream of snapshot
-     * @return last processed zxid
-     */
-    public synchronized long restoreFromSnapshot(final InputStream inputStream) throws IOException {
-        if (inputStream == null) {
-            throw new IllegalArgumentException("InputStream can not be null when restoring from snapshot");
-        }
-
-        long start = Time.currentElapsedTime();
-        LOG.info("Before restore database. lastProcessedZxid={}, nodeCount={}，sessionCount={}",
-            getZKDatabase().getDataTreeLastProcessedZxid(),
-            getZKDatabase().dataTree.getNodeCount(),
-            getZKDatabase().getSessionCount());
-
-        // restore to a new zkDatabase
-        final ZKDatabase newZKDatabase = new ZKDatabase(this.txnLogFactory);
-        final CheckedInputStream cis = new CheckedInputStream(new BufferedInputStream(inputStream), new Adler32());
-        final InputArchive ia = BinaryInputArchive.getArchive(cis);
-        newZKDatabase.deserializeSnapshot(ia, cis);
-        LOG.info("Restored to a new database. lastProcessedZxid={}, nodeCount={}, sessionCount={}",
-            newZKDatabase.getDataTreeLastProcessedZxid(),
-            newZKDatabase.dataTree.getNodeCount(),
-            newZKDatabase.getSessionCount());
-
-        // create a CountDownLatch
-        restoreLatch = new CountDownLatch(1);
-
-        try {
-            // set to the new zkDatabase
-            setZKDatabase(newZKDatabase);
-
-            // re-create SessionTrack
-            createSessionTracker();
-        } finally {
-            // unblock request submission
-            restoreLatch.countDown();
-            restoreLatch = null;
-        }
-
-        LOG.info("After restore database. lastProcessedZxid={}, nodeCount={}, sessionCount={}",
-                getZKDatabase().getDataTreeLastProcessedZxid(),
-                getZKDatabase().dataTree.getNodeCount(),
-                getZKDatabase().getSessionCount());
-
-        long elapsed = Time.currentElapsedTime() - start;
-        LOG.info("Restore taken in {} ms", elapsed);
-        ServerMetrics.getMetrics().RESTORE_TIME.add(elapsed);
-
-        return getLastProcessedZxid();
-    }
-
-    public boolean shouldForceWriteInitialSnapshotAfterLeaderElection() {
-        return txnLogFactory.shouldForceWriteInitialSnapshotAfterLeaderElection();
-    }
-
-    @Override
-    public long getDataDirSize() {
-        if (zkDb == null) {
-            return 0L;
-        }
-        File path = zkDb.snapLog.getSnapDir();
-        return getDirSize(path);
-    }
-
-    @Override
-    public long getLogDirSize() {
-        if (zkDb == null) {
-            return 0L;
-        }
-        File path = zkDb.snapLog.getDataLogDir();
-        return getDirSize(path);
-    }
-
-    private long getDirSize(File file) {
-        long size = 0L;
-        if (file.isDirectory()) {
-            File[] files = file.listFiles();
-            if (files != null) {
-                for (File f : files) {
-                    size += getDirSize(f);
-                }
-            }
-        } else {
-            size = file.length();
-        }
-        return size;
-    }
-
-    public long getZxid() {
-        return hzxid.get();
-    }
-
-    public SessionTracker getSessionTracker() {
-        return sessionTracker;
-    }
-
-    long getNextZxid() {
-        return hzxid.incrementAndGet();
-    }
-
-    public void setZxid(long zxid) {
-        hzxid.set(zxid);
-    }
-
-    private void close(long sessionId) {
-        Request si = new Request(null, sessionId, 0, OpCode.closeSession, null, null);
-        submitRequest(si);
-    }
-
-    public void closeSession(long sessionId) {
-        LOG.info("Closing session 0x{}", Long.toHexString(sessionId));
-
-        // we do not want to wait for a session close. send it as soon as we
-        // detect it!
-        close(sessionId);
-    }
-
-    protected void killSession(long sessionId, long zxid) {
-        zkDb.killSession(sessionId, zxid);
-        if (LOG.isTraceEnabled()) {
-            ZooTrace.logTraceMessage(
-                LOG,
-                ZooTrace.SESSION_TRACE_MASK,
-                "ZooKeeperServer --- killSession: 0x" + Long.toHexString(sessionId));
-        }
-        if (sessionTracker != null) {
-            sessionTracker.removeSession(sessionId);
-        }
-    }
-
-    public void expire(Session session) {
-        long sessionId = session.getSessionId();
-        LOG.info(
-            "Expiring session 0x{}, timeout of {}ms exceeded",
-            Long.toHexString(sessionId),
-            session.getTimeout());
-        close(sessionId);
-    }
-
-    public void expire(long sessionId) {
-        LOG.info("forcibly expiring session 0x{}", Long.toHexString(sessionId));
-
-        close(sessionId);
-    }
-
-    public static class MissingSessionException extends IOException {
-
-        private static final long serialVersionUID = 7467414635467261007L;
-
-        public MissingSessionException(String msg) {
-            super(msg);
-        }
-
-    }
-
-    void touch(ServerCnxn cnxn) throws MissingSessionException {
-        if (cnxn == null) {
-            return;
-        }
-        long id = cnxn.getSessionId();
-        int to = cnxn.getSessionTimeout();
-        if (!sessionTracker.touchSession(id, to)) {
-            throw new MissingSessionException("No session with sessionid 0x"
-                                              + Long.toHexString(id)
-                                              + " exists, probably expired and removed");
-        }
-    }
-
-    protected void registerJMX() {
-        // register with JMX
-        try {
-            jmxServerBean = new ZooKeeperServerBean(this);
-            MBeanRegistry.getInstance().register(jmxServerBean, null);
-
-            try {
-                jmxDataTreeBean = new DataTreeBean(zkDb.getDataTree());
-                MBeanRegistry.getInstance().register(jmxDataTreeBean, jmxServerBean);
-            } catch (Exception e) {
-                LOG.warn("Failed to register with JMX", e);
-                jmxDataTreeBean = null;
-            }
-        } catch (Exception e) {
-            LOG.warn("Failed to register with JMX", e);
-            jmxServerBean = null;
-        }
-    }
-
-    public void startdata() throws IOException, InterruptedException {
-        //check to see if zkDb is not null
-        if (zkDb == null) {
-            zkDb = new ZKDatabase(this.txnLogFactory);
-        }
-        if (!zkDb.isInitialized()) {
-            loadData();
-        }
-    }
-
-    public synchronized void startup() {
-        startupWithServerState(State.RUNNING);
-    }
-
-    public synchronized void startupWithoutServing() {
-        startupWithServerState(State.INITIAL);
-    }
-
-    public synchronized void startServing() {
-        setState(State.RUNNING);
-        notifyAll();
-    }
-
-    private void startupWithServerState(State state) {
-        if (sessionTracker == null) {
-            createSessionTracker();
-        }
-        startSessionTracker();
-        setupRequestProcessors();
-
-        startRequestThrottler();
-
-        registerJMX();
-
-        startJvmPauseMonitor();
-
-        registerMetrics();
-
-        setState(state);
-
-        requestPathMetricsCollector.start();
-
-        localSessionEnabled = sessionTracker.isLocalSessionsEnabled();
-
-        notifyAll();
-    }
-
-    protected void startJvmPauseMonitor() {
-        if (this.jvmPauseMonitor != null) {
-            this.jvmPauseMonitor.serviceStart();
-        }
-    }
-
-    protected void startRequestThrottler() {
-        requestThrottler = createRequestThrottler();
-        requestThrottler.start();
-    }
-
-    protected RequestThrottler createRequestThrottler() {
-        return new RequestThrottler(this);
-    }
-
-    protected void setupRequestProcessors() {
-        RequestProcessor finalProcessor = new FinalRequestProcessor(this);
-        RequestProcessor syncProcessor = new SyncRequestProcessor(this, finalProcessor);
-        ((SyncRequestProcessor) syncProcessor).start();
-        firstProcessor = new PrepRequestProcessor(this, syncProcessor);
-        ((PrepRequestProcessor) firstProcessor).start();
-    }
-
-    public ZooKeeperServerListener getZooKeeperServerListener() {
-        return listener;
-    }
-
-    /**
-     * Change the server ID used by {@link #createSessionTracker()}. Must be called prior to
-     * {@link #startup()} being called
-     *
-     * @param newId ID to use
-     */
-    public void setCreateSessionTrackerServerId(int newId) {
-        createSessionTrackerServerId = newId;
-    }
-
-    protected void createSessionTracker() {
-        sessionTracker = new SessionTrackerImpl(this, zkDb.getSessionWithTimeOuts(), tickTime, createSessionTrackerServerId, getZooKeeperServerListener());
-    }
-
-    protected void startSessionTracker() {
-        ((SessionTrackerImpl) sessionTracker).start();
-    }
-
-    /**
-     * Sets the state of ZooKeeper server. After changing the state, it notifies
-     * the server state change to a registered shutdown handler, if any.
-     * <p>
-     * The following are the server state transitions:
-     * <ul><li>During startup the server will be in the INITIAL state.</li>
-     * <li>After successfully starting, the server sets the state to RUNNING.
-     * </li>
-     * <li>The server transitions to the ERROR state if it hits an internal
-     * error. {@link ZooKeeperServerListenerImpl} notifies any critical resource
-     * error events, e.g., SyncRequestProcessor not being able to write a txn to
-     * disk.</li>
-     * <li>During shutdown the server sets the state to SHUTDOWN, which
-     * corresponds to the server not running.</li>
-     *
-     * <li>During maintenance (e.g. restore) the server sets the state to MAINTENANCE
-     * </li></ul>
-     *
-     * @param state new server state.
-     */
-    protected void setState(State state) {
-        this.state = state;
-        // Notify server state changes to the registered shutdown handler, if any.
-        if (zkShutdownHandler != null) {
-            zkShutdownHandler.handle(state);
-        } else {
-            LOG.debug(
-                "ZKShutdownHandler is not registered, so ZooKeeper server"
-                    + " won't take any action on ERROR or SHUTDOWN server state changes");
-        }
-    }
-
-    /**
-     * This can be used while shutting down the server to see whether the server
-     * is already shutdown or not.
-     *
-     * @return true if the server is running or server hits an error, false
-     *         otherwise.
-     */
-    protected boolean canShutdown() {
-        return state == State.RUNNING || state == State.ERROR;
-    }
-
-    /**
-     * @return true if the server is running, false otherwise.
-     */
-    public boolean isRunning() {
-        return state == State.RUNNING;
-    }
-
-    public void shutdown() {
-        shutdown(false);
-    }
-
-    /**
-     * Shut down the server instance
-     * @param fullyShutDown true if another server using the same database will not replace this one in the same process
-     */
-    public synchronized void shutdown(boolean fullyShutDown) {
-        if (!canShutdown()) {
-            if (fullyShutDown && zkDb != null) {
-                zkDb.clear();
-            }
-            LOG.debug("ZooKeeper server is not running, so not proceeding to shutdown!");
-            return;
-        }
-        LOG.info("shutting down");
-
-        // new RuntimeException("Calling shutdown").printStackTrace();
-        setState(State.SHUTDOWN);
-
-        // unregister all metrics that are keeping a strong reference to this object
-        // subclasses will do their specific clean up
-        unregisterMetrics();
-
-        if (requestThrottler != null) {
-            requestThrottler.shutdown();
-        }
-
-        // Since sessionTracker and syncThreads poll we just have to
-        // set running to false and they will detect it during the poll
-        // interval.
-        if (sessionTracker != null) {
-            sessionTracker.shutdown();
-        }
-        if (firstProcessor != null) {
-            firstProcessor.shutdown();
-        }
-        if (jvmPauseMonitor != null) {
-            jvmPauseMonitor.serviceStop();
-        }
-
-        if (zkDb != null) {
-            if (fullyShutDown) {
-                zkDb.clear();
-            } else {
-                // else there is no need to clear the database
-                //  * When a new quorum is established we can still apply the diff
-                //    on top of the same zkDb data
-                //  * If we fetch a new snapshot from leader, the zkDb will be
-                //    cleared anyway before loading the snapshot
-                try {
-                    // This will fast-forward the database to the latest recorded transactions
-                    zkDb.fastForwardDataBase();
-                } catch (IOException e) {
-                    LOG.error("Error updating DB", e);
-                    zkDb.clear();
-                }
-            }
-        }
-
-        requestPathMetricsCollector.shutdown();
-        unregisterJMX();
-    }
-
-    protected void unregisterJMX() {
-        // unregister from JMX
-        try {
-            if (jmxDataTreeBean != null) {
-                MBeanRegistry.getInstance().unregister(jmxDataTreeBean);
-            }
-        } catch (Exception e) {
-            LOG.warn("Failed to unregister with JMX", e);
-        }
-        try {
-            if (jmxServerBean != null) {
-                MBeanRegistry.getInstance().unregister(jmxServerBean);
-            }
-        } catch (Exception e) {
-            LOG.warn("Failed to unregister with JMX", e);
-        }
-        jmxServerBean = null;
-        jmxDataTreeBean = null;
-    }
-
-    public void incInProcess() {
-        requestsInProcess.incrementAndGet();
-    }
-
-    public void decInProcess() {
-        requestsInProcess.decrementAndGet();
-        if (requestThrottler != null) {
-            requestThrottler.throttleWake();
-        }
-    }
-
-    public int getInProcess() {
-        return requestsInProcess.get();
-    }
-
-    public int getInflight() {
-        return requestThrottleInflight();
-    }
-
-    private int requestThrottleInflight() {
-        if (requestThrottler != null) {
-            return requestThrottler.getInflight();
-        }
-        return 0;
-    }
-
-    static class PrecalculatedDigest {
-        final long nodeDigest;
-        final long treeDigest;
-
-        PrecalculatedDigest(long nodeDigest, long treeDigest) {
-            this.nodeDigest = nodeDigest;
-            this.treeDigest = treeDigest;
-        }
-    }
-
-
-    /**
-     * This structure is used to facilitate information sharing between PrepRP
-     * and FinalRP.
-     */
-    static class ChangeRecord {
-        PrecalculatedDigest precalculatedDigest;
-        byte[] data;
-
-        ChangeRecord(long zxid, String path, StatPersisted stat, int childCount, List<ACL> acl) {
-            this.zxid = zxid;
-            this.path = path;
-            this.stat = stat;
-            this.childCount = childCount;
-            this.acl = acl;
-        }
-
-        long zxid;
-
-        String path;
-
-        StatPersisted stat; /* Make sure to create a new object when changing */
-
-        int childCount;
-
-        List<ACL> acl; /* Make sure to create a new object when changing */
-
-        ChangeRecord duplicate(long zxid) {
-            StatPersisted stat = new StatPersisted();
-            if (this.stat != null) {
-                DataTree.copyStatPersisted(this.stat, stat);
-            }
-            ChangeRecord changeRecord = new ChangeRecord(zxid, path, stat, childCount,
-                    acl == null ? new ArrayList<>() : new ArrayList<>(acl));
-            changeRecord.precalculatedDigest = precalculatedDigest;
-            changeRecord.data = data;
-            return changeRecord;
-        }
-
-    }
-
-    byte[] generatePasswd(long id) {
-        Random r = new Random(id ^ superSecret);
-        byte[] p = new byte[16];
-        r.nextBytes(p);
-        return p;
-    }
-
-    protected boolean checkPasswd(long sessionId, byte[] passwd) {
-        return sessionId != 0 && Arrays.equals(passwd, generatePasswd(sessionId));
-    }
-
-    long createSession(ServerCnxn cnxn, byte[] passwd, int timeout) {
-        if (passwd == null) {
-            // Possible since it's just deserialized from a packet on the wire.
-            passwd = new byte[0];
-        }
-        long sessionId = sessionTracker.createSession(timeout);
-        Random r = new Random(sessionId ^ superSecret);
-        r.nextBytes(passwd);
-        CreateSessionTxn txn = new CreateSessionTxn(timeout);
-        cnxn.setSessionId(sessionId);
-        Request si = new Request(cnxn, sessionId, 0, OpCode.createSession, RequestRecord.fromRecord(txn), null);
-        submitRequest(si);
-        return sessionId;
-    }
-
-    /**
-     * set the owner of this session as owner
-     * @param id the session id
-     * @param owner the owner of the session
-     * @throws SessionExpiredException
-     */
-    public void setOwner(long id, Object owner) throws SessionExpiredException {
-        sessionTracker.setOwner(id, owner);
-    }
-
-    protected void revalidateSession(ServerCnxn cnxn, long sessionId, int sessionTimeout) throws IOException {
-        boolean rc = sessionTracker.touchSession(sessionId, sessionTimeout);
-        if (LOG.isTraceEnabled()) {
-            ZooTrace.logTraceMessage(
-                LOG,
-                ZooTrace.SESSION_TRACE_MASK,
-                "Session 0x" + Long.toHexString(sessionId) + " is valid: " + rc);
-        }
-        finishSessionInit(cnxn, rc);
-    }
-
-    public void reopenSession(ServerCnxn cnxn, long sessionId, byte[] passwd, int sessionTimeout) throws IOException {
-        if (checkPasswd(sessionId, passwd)) {
-            revalidateSession(cnxn, sessionId, sessionTimeout);
-        } else {
-            LOG.warn(
-                "Incorrect password from {} for session 0x{}",
-                cnxn.getRemoteSocketAddress(),
-                Long.toHexString(sessionId));
-            finishSessionInit(cnxn, false);
-        }
-    }
-
-    public void finishSessionInit(ServerCnxn cnxn, boolean valid) {
-        // register with JMX
-        try {
-            if (valid) {
-                if (serverCnxnFactory != null && serverCnxnFactory.cnxns.contains(cnxn)) {
-                    serverCnxnFactory.registerConnection(cnxn);
-                } else if (secureServerCnxnFactory != null && secureServerCnxnFactory.cnxns.contains(cnxn)) {
-                    secureServerCnxnFactory.registerConnection(cnxn);
-                }
-            }
-        } catch (Exception e) {
-            LOG.warn("Failed to register with JMX", e);
-        }
-
-        try {
-            ConnectResponse rsp = new ConnectResponse(
-                0,
-                valid ? cnxn.getSessionTimeout() : 0,
-                valid ? cnxn.getSessionId() : 0, // send 0 if session is no
-                // longer valid
-                valid ? generatePasswd(cnxn.getSessionId()) : new byte[16],
-                this instanceof ReadOnlyZooKeeperServer);
-            ByteArrayOutputStream baos = new ByteArrayOutputStream();
-            BinaryOutputArchive bos = BinaryOutputArchive.getArchive(baos);
-            bos.writeInt(-1, "len");
-            rsp.serialize(bos, "connect");
-            baos.close();
-            ByteBuffer bb = ByteBuffer.wrap(baos.toByteArray());
-            bb.putInt(bb.remaining() - 4).rewind();
-            cnxn.sendBuffer(bb);
-
-            if (valid) {
-                LOG.debug(
-                    "Established session 0x{} with negotiated timeout {} for client {}",
-                    Long.toHexString(cnxn.getSessionId()),
-                    cnxn.getSessionTimeout(),
-                    cnxn.getRemoteSocketAddress());
-                cnxn.enableRecv();
-            } else {
-
-                LOG.info(
-                    "Invalid session 0x{} for client {}, probably expired",
-                    Long.toHexString(cnxn.getSessionId()),
-                    cnxn.getRemoteSocketAddress());
-                cnxn.sendBuffer(ServerCnxnFactory.closeConn);
-            }
-
-        } catch (Exception e) {
-            LOG.warn("Exception while establishing session, closing", e);
-            cnxn.close(ServerCnxn.DisconnectReason.IO_EXCEPTION_IN_SESSION_INIT);
-        }
-    }
-
-    public void closeSession(ServerCnxn cnxn, RequestHeader requestHeader) {
-        closeSession(cnxn.getSessionId());
-    }
-
-    public long getServerId() {
-        return 0;
-    }
-
-    /**
-     * If the underlying Zookeeper server support local session, this method
-     * will set a isLocalSession to true if a request is associated with
-     * a local session.
-     *
-     * @param si
-     */
-    protected void setLocalSessionFlag(Request si) {
-    }
-
-    public void submitRequest(Request si) {
-        if (restoreLatch != null) {
-            try {
-                LOG.info("Blocking request submission while restore is in progress");
-                restoreLatch.await();
-            } catch (final InterruptedException e) {
-                LOG.warn("Unexpected interruption", e);
-            }
-        }
-        enqueueRequest(si);
-    }
-
-    public void enqueueRequest(Request si) {
-        if (requestThrottler == null) {
-            synchronized (this) {
-                try {
-                    // Since all requests are passed to the request
-                    // processor it should wait for setting up the request
-                    // processor chain. The state will be updated to RUNNING
-                    // after the setup.
-                    while (state == State.INITIAL) {
-                        wait(1000);
-                    }
-                } catch (InterruptedException e) {
-                    LOG.warn("Unexpected interruption", e);
-                }
-                if (requestThrottler == null) {
-                    throw new RuntimeException("Not started");
-                }
-            }
-        }
-        requestThrottler.submitRequest(si);
-    }
-
-    public void submitRequestNow(Request si) {
-        if (firstProcessor == null) {
-            synchronized (this) {
-                try {
-                    // Since all requests are passed to the request
-                    // processor it should wait for setting up the request
-                    // processor chain. The state will be updated to RUNNING
-                    // after the setup.
-                    while (state == State.INITIAL) {
-                        wait(1000);
-                    }
-                } catch (InterruptedException e) {
-                    LOG.warn("Unexpected interruption", e);
-                }
-                if (firstProcessor == null || state != State.RUNNING) {
-                    throw new RuntimeException("Not started");
-                }
-            }
-        }
-        try {
-            touch(si.cnxn);
-            boolean validpacket = Request.isValid(si.type);
-            if (validpacket) {
-                setLocalSessionFlag(si);
-                firstProcessor.processRequest(si);
-                if (si.cnxn != null) {
-                    incInProcess();
-                }
-            } else {
-                LOG.warn("Received packet at server of unknown type {}", si.type);
-                // Update request accounting/throttling limits
-                requestFinished(si);
-                new UnimplementedRequestProcessor().processRequest(si);
-            }
-        } catch (MissingSessionException e) {
-            LOG.debug("Dropping request.", e);
-            // Update request accounting/throttling limits
-            requestFinished(si);
-        } catch (RequestProcessorException e) {
-            LOG.error("Unable to process request", e);
-            // Update request accounting/throttling limits
-            requestFinished(si);
-        }
-    }
-
-    public static int getSnapCount() {
-        int snapCount = Integer.getInteger(SNAP_COUNT, DEFAULT_SNAP_COUNT);
-        // snapCount must be 2 or more. See org.apache.zookeeper.server.SyncRequestProcessor
-        if (snapCount < 2) {
-            LOG.warn("SnapCount should be 2 or more. Now, snapCount is reset to 2");
-            snapCount = 2;
-        }
-        return snapCount;
-    }
-
-    public int getGlobalOutstandingLimit() {
-        return Integer.getInteger(GLOBAL_OUTSTANDING_LIMIT, DEFAULT_GLOBAL_OUTSTANDING_LIMIT);
-    }
-
-    public static long getSnapSizeInBytes() {
-        long size = Long.getLong("zookeeper.snapSizeLimitInKb", 4194304L); // 4GB by default
-        if (size <= 0) {
-            LOG.info("zookeeper.snapSizeLimitInKb set to a non-positive value {}; disabling feature", size);
-        }
-        return size * 1024; // Convert to bytes
-    }
-
-    public void setServerCnxnFactory(ServerCnxnFactory factory) {
-        serverCnxnFactory = factory;
-    }
-
-    public ServerCnxnFactory getServerCnxnFactory() {
-        return serverCnxnFactory;
-    }
-
-    public ServerCnxnFactory getSecureServerCnxnFactory() {
-        return secureServerCnxnFactory;
-    }
-
-    public void setSecureServerCnxnFactory(ServerCnxnFactory factory) {
-        secureServerCnxnFactory = factory;
-    }
-
-    /**
-     * return the last processed id from the
-     * datatree
-     */
-    public long getLastProcessedZxid() {
-        return zkDb.getDataTreeLastProcessedZxid();
-    }
-
-    /**
-     * return the outstanding requests
-     * in the queue, which haven't been
-     * processed yet
-     */
-    public long getOutstandingRequests() {
-        return getInProcess();
-    }
-
-    /**
-     * return the total number of client connections that are alive
-     * to this server
-     */
-    public int getNumAliveConnections() {
-        int numAliveConnections = 0;
-
-        if (serverCnxnFactory != null) {
-            numAliveConnections += serverCnxnFactory.getNumAliveConnections();
-        }
-
-        if (secureServerCnxnFactory != null) {
-            numAliveConnections += secureServerCnxnFactory.getNumAliveConnections();
-        }
-
-        return numAliveConnections;
-    }
-
-    /**
-     * truncate the log to get in sync with others
-     * if in a quorum
-     * @param zxid the zxid that it needs to get in sync
-     * with others
-     * @throws IOException
-     */
-    public void truncateLog(long zxid) throws IOException {
-        this.zkDb.truncateLog(zxid);
-    }
-
-    public int getTickTime() {
-        return tickTime;
-    }
-
-    public void setTickTime(int tickTime) {
-        LOG.info("tickTime set to {} ms", tickTime);
-        this.tickTime = tickTime;
-    }
-
-    public static int getThrottledOpWaitTime() {
-        return throttledOpWaitTime;
-    }
-
-    public static void setThrottledOpWaitTime(int time) {
-        LOG.info("throttledOpWaitTime set to {} ms", time);
-        throttledOpWaitTime = time;
-    }
-
-    public int getMinSessionTimeout() {
-        return minSessionTimeout;
-    }
-
-    public void setMinSessionTimeout(int min) {
-        this.minSessionTimeout = min == -1 ? tickTime * 2 : min;
-        LOG.info("minSessionTimeout set to {} ms", this.minSessionTimeout);
-    }
-
-    public int getMaxSessionTimeout() {
-        return maxSessionTimeout;
-    }
-
-    public void setMaxSessionTimeout(int max) {
-        this.maxSessionTimeout = max == -1 ? tickTime * 20 : max;
-        LOG.info("maxSessionTimeout set to {} ms", this.maxSessionTimeout);
-    }
-
-    public int getClientPortListenBacklog() {
-        return listenBacklog;
-    }
-
-    public void setClientPortListenBacklog(int backlog) {
-        this.listenBacklog = backlog;
-        LOG.info("clientPortListenBacklog set to {}", backlog);
-    }
-
-    public int getClientPort() {
-        return serverCnxnFactory != null ? serverCnxnFactory.getLocalPort() : -1;
-    }
-
-    public int getSecureClientPort() {
-        return secureServerCnxnFactory != null ? secureServerCnxnFactory.getLocalPort() : -1;
-    }
-
-    /** Maximum number of connections allowed from particular host (ip) */
-    public int getMaxClientCnxnsPerHost() {
-        if (serverCnxnFactory != null) {
-            return serverCnxnFactory.getMaxClientCnxnsPerHost();
-        }
-        if (secureServerCnxnFactory != null) {
-            return secureServerCnxnFactory.getMaxClientCnxnsPerHost();
-        }
-        return -1;
-    }
-
-    public void setTxnLogFactory(FileTxnSnapLog txnLog) {
-        this.txnLogFactory = txnLog;
-    }
-
-    public FileTxnSnapLog getTxnLogFactory() {
-        return this.txnLogFactory;
-    }
-
-    /**
-     * Returns the elapsed sync of time of transaction log in milliseconds.
-     */
-    public long getTxnLogElapsedSyncTime() {
-        return txnLogFactory.getTxnLogElapsedSyncTime();
-    }
-
-    public String getState() {
-        return "standalone";
-    }
-
-    public void dumpEphemerals(PrintWriter pwriter) {
-        zkDb.dumpEphemerals(pwriter);
-    }
-
-    public Map<Long, Set<String>> getEphemerals() {
-        return zkDb.getEphemerals();
-    }
-
-    public double getConnectionDropChance() {
-        return connThrottle.getDropChance();
-    }
-
-    public void processConnectRequest(ServerCnxn cnxn, ConnectRequest request) throws IOException, ClientCnxnLimitException {
-        LOG.debug(
-            "Session establishment request from client {} client's lastZxid is 0x{}",
-            cnxn.getRemoteSocketAddress(),
-            Long.toHexString(request.getLastZxidSeen()));
-
-        long sessionId = request.getSessionId();
-        int tokensNeeded = 1;
-        if (connThrottle.isConnectionWeightEnabled()) {
-            if (sessionId == 0) {
-                if (localSessionEnabled) {
-                    tokensNeeded = connThrottle.getRequiredTokensForLocal();
-                } else {
-                    tokensNeeded = connThrottle.getRequiredTokensForGlobal();
-                }
-            } else {
-                tokensNeeded = connThrottle.getRequiredTokensForRenew();
-            }
-        }
-
-        if (!connThrottle.checkLimit(tokensNeeded)) {
-            throw new ClientCnxnLimitException();
-        }
-        ServerMetrics.getMetrics().CONNECTION_TOKEN_DEFICIT.add(connThrottle.getDeficit());
-        ServerMetrics.getMetrics().CONNECTION_REQUEST_COUNT.add(1);
-
-        if (!cnxn.protocolManager.isReadonlyAvailable()) {
-            LOG.warn(
-                "Connection request from old client {}; will be dropped if server is in r-o mode",
-                cnxn.getRemoteSocketAddress());
-        }
-
-        if (!request.getReadOnly() && this instanceof ReadOnlyZooKeeperServer) {
-            String msg = "Refusing session request for not-read-only client " + cnxn.getRemoteSocketAddress();
-            LOG.info(msg);
-            throw new CloseRequestException(msg, ServerCnxn.DisconnectReason.NOT_READ_ONLY_CLIENT);
-        }
-        if (request.getLastZxidSeen() > zkDb.dataTree.lastProcessedZxid) {
-            String msg = "Refusing session(0x"
-                         + Long.toHexString(sessionId)
-                         + ") request for client "
-                         + cnxn.getRemoteSocketAddress()
-                         + " as it has seen zxid 0x"
-                         + Long.toHexString(request.getLastZxidSeen())
-                         + " our last zxid is 0x"
-                         + Long.toHexString(getZKDatabase().getDataTreeLastProcessedZxid())
-                         + " client must try another server";
-
-            LOG.info(msg);
-            throw new CloseRequestException(msg, ServerCnxn.DisconnectReason.CLIENT_ZXID_AHEAD);
-        }
-        int sessionTimeout = request.getTimeOut();
-        byte[] passwd = request.getPasswd();
-        int minSessionTimeout = getMinSessionTimeout();
-        if (sessionTimeout < minSessionTimeout) {
-            sessionTimeout = minSessionTimeout;
-        }
-        int maxSessionTimeout = getMaxSessionTimeout();
-        if (sessionTimeout > maxSessionTimeout) {
-            sessionTimeout = maxSessionTimeout;
-        }
-        cnxn.setSessionTimeout(sessionTimeout);
-        // We don't want to receive any packets until we are sure that the
-        // session is setup
-        cnxn.disableRecv();
-        if (sessionId == 0) {
-            long id = createSession(cnxn, passwd, sessionTimeout);
-            LOG.debug(
-                "Client attempting to establish new session: session = 0x{}, zxid = 0x{}, timeout = {}, address = {}",
-                Long.toHexString(id),
-                Long.toHexString(request.getLastZxidSeen()),
-                request.getTimeOut(),
-                cnxn.getRemoteSocketAddress());
-        } else {
-            validateSession(cnxn, sessionId);
-            LOG.debug(
-                "Client attempting to renew session: session = 0x{}, zxid = 0x{}, timeout = {}, address = {}",
-                Long.toHexString(sessionId),
-                Long.toHexString(request.getLastZxidSeen()),
-                request.getTimeOut(),
-                cnxn.getRemoteSocketAddress());
-            if (serverCnxnFactory != null) {
-                serverCnxnFactory.closeSession(sessionId, ServerCnxn.DisconnectReason.CLIENT_RECONNECT);
-            }
-            if (secureServerCnxnFactory != null) {
-                secureServerCnxnFactory.closeSession(sessionId, ServerCnxn.DisconnectReason.CLIENT_RECONNECT);
-            }
-            cnxn.setSessionId(sessionId);
-            reopenSession(cnxn, sessionId, passwd, sessionTimeout);
-            ServerMetrics.getMetrics().CONNECTION_REVALIDATE_COUNT.add(1);
-
-        }
-    }
-
-    /**
-     * Validate if a particular session can be reestablished.
-     *
-     * @param cnxn
-     * @param sessionId
-     */
-    protected void validateSession(ServerCnxn cnxn, long sessionId)
-            throws IOException {
-        // do nothing
-    }
-
-    public boolean shouldThrottle(long outStandingCount) {
-        int globalOutstandingLimit = getGlobalOutstandingLimit();
-        if (globalOutstandingLimit < getInflight() || globalOutstandingLimit < getInProcess()) {
-            return outStandingCount > 0;
-        }
-        return false;
-    }
-
-    long getFlushDelay() {
-        return flushDelay;
-    }
-
-    static void setFlushDelay(long delay) {
-        LOG.info("{} = {} ms", FLUSH_DELAY, delay);
-        flushDelay = delay;
-    }
-
-    long getMaxWriteQueuePollTime() {
-        return maxWriteQueuePollTime;
-    }
-
-    static void setMaxWriteQueuePollTime(long maxTime) {
-        LOG.info("{} = {} ms", MAX_WRITE_QUEUE_POLL_SIZE, maxTime);
-        maxWriteQueuePollTime = maxTime;
-    }
-
-    int getMaxBatchSize() {
-        return maxBatchSize;
-    }
-
-    static void setMaxBatchSize(int size) {
-        LOG.info("{}={}", MAX_BATCH_SIZE, size);
-        maxBatchSize = size;
-    }
-
-    private void initLargeRequestThrottlingSettings() {
-        setLargeRequestMaxBytes(Integer.getInteger("zookeeper.largeRequestMaxBytes", largeRequestMaxBytes));
-        setLargeRequestThreshold(Integer.getInteger("zookeeper.largeRequestThreshold", -1));
-    }
-
-    public int getLargeRequestMaxBytes() {
-        return largeRequestMaxBytes;
-    }
-
-    public void setLargeRequestMaxBytes(int bytes) {
-        if (bytes <= 0) {
-            LOG.warn("Invalid max bytes for all large requests {}. It should be a positive number.", bytes);
-            LOG.warn("Will not change the setting. The max bytes stay at {}", largeRequestMaxBytes);
-        } else {
-            largeRequestMaxBytes = bytes;
-            LOG.info("The max bytes for all large requests are set to {}", largeRequestMaxBytes);
-        }
-    }
-
-    public int getLargeRequestThreshold() {
-        return largeRequestThreshold;
-    }
-
-    public void setLargeRequestThreshold(int threshold) {
-        if (threshold == 0 || threshold < -1) {
-            LOG.warn("Invalid large request threshold {}. It should be -1 or positive. Setting to -1 ", threshold);
-            largeRequestThreshold = -1;
-        } else {
-            largeRequestThreshold = threshold;
-            LOG.info("The large request threshold is set to {}", largeRequestThreshold);
-        }
-    }
-
-    public int getLargeRequestBytes() {
-        return currentLargeRequestBytes.get();
-    }
-
-    private boolean isLargeRequest(int length) {
-        // The large request limit is disabled when threshold is -1
-        if (largeRequestThreshold == -1) {
-            return false;
-        }
-        return length > largeRequestThreshold;
-    }
-
-    public boolean checkRequestSizeWhenReceivingMessage(int length) throws IOException {
-        if (!isLargeRequest(length)) {
-            return true;
-        }
-        if (currentLargeRequestBytes.get() + length <= largeRequestMaxBytes) {
-            return true;
-        } else {
-            ServerMetrics.getMetrics().LARGE_REQUESTS_REJECTED.add(1);
-            throw new IOException("Rejecting large request");
-        }
-
-    }
-
-    private boolean checkRequestSizeWhenMessageReceived(int length) throws IOException {
-        if (!isLargeRequest(length)) {
-            return true;
-        }
-
-        int bytes = currentLargeRequestBytes.addAndGet(length);
-        if (bytes > largeRequestMaxBytes) {
-            currentLargeRequestBytes.addAndGet(-length);
-            ServerMetrics.getMetrics().LARGE_REQUESTS_REJECTED.add(1);
-            throw new IOException("Rejecting large request");
-        }
-        return true;
-    }
-
-    public void requestFinished(Request request) {
-        int largeRequestLength = request.getLargeRequestSize();
-        if (largeRequestLength != -1) {
-            currentLargeRequestBytes.addAndGet(-largeRequestLength);
-        }
-    }
-
-    public void processPacket(ServerCnxn cnxn, RequestHeader h, RequestRecord request) throws IOException {
-        // Need to increase the outstanding request count first, otherwise
-        // there might be a race condition that it enabled recv after
-        // processing request and then disabled when check throttling.
-        //
-        // Be aware that we're actually checking the global outstanding
-        // request before this request.
-        //
-        // It's fine if the IOException thrown before we decrease the count
-        // in cnxn, since it will close the cnxn anyway.
-        cnxn.incrOutstandingAndCheckThrottle(h);
-
-        if (h.getType() == OpCode.auth) {
-            LOG.info("got auth packet {}", cnxn.getRemoteSocketAddress());
-            AuthPacket authPacket = request.readRecord(AuthPacket::new);
-            String scheme = authPacket.getScheme();
-            ServerAuthenticationProvider ap = ProviderRegistry.getServerProvider(scheme);
-            Code authReturn = KeeperException.Code.AUTHFAILED;
-            if (ap != null) {
-                try {
-                    // handleAuthentication may close the connection, to allow the client to choose
-                    // a different server to connect to.
-                    authReturn = ap.handleAuthentication(
-                        new ServerAuthenticationProvider.ServerObjs(this, cnxn),
-                        authPacket.getAuth());
-                } catch (RuntimeException e) {
-                    LOG.warn("Caught runtime exception from AuthenticationProvider: {}", scheme, e);
-                    authReturn = KeeperException.Code.AUTHFAILED;
-                }
-            }
-            if (authReturn == KeeperException.Code.OK) {
-                LOG.info("Session 0x{}: auth success for scheme {} and address {}",
-                        Long.toHexString(cnxn.getSessionId()), scheme,
-                        cnxn.getRemoteSocketAddress());
-                ReplyHeader rh = new ReplyHeader(h.getXid(), 0, KeeperException.Code.OK.intValue());
-                cnxn.sendResponse(rh, null, null);
-            } else {
-                if (ap == null) {
-                    LOG.warn(
-                        "No authentication provider for scheme: {} has {}",
-                        scheme,
-                        ProviderRegistry.listProviders());
-                } else {
-                    LOG.warn("Authentication failed for scheme: {}", scheme);
-                }
-                // send a response...
-                ReplyHeader rh = new ReplyHeader(h.getXid(), 0, KeeperException.Code.AUTHFAILED.intValue());
-                cnxn.sendResponse(rh, null, null);
-                // ... and close connection
-                cnxn.sendBuffer(ServerCnxnFactory.closeConn);
-                cnxn.disableRecv();
-            }
-            return;
-        } else if (h.getType() == OpCode.sasl) {
-            processSasl(request, cnxn, h);
-        } else {
-            if (!authHelper.enforceAuthentication(cnxn, h.getXid())) {
-                // Authentication enforcement is failed
-                // Already sent response to user about failure and closed the session, lets return
-                return;
-            } else {
-                Request si = new Request(cnxn, cnxn.getSessionId(), h.getXid(), h.getType(), request, cnxn.getAuthInfo());
-                int length = request.limit();
-                if (isLargeRequest(length)) {
-                    // checkRequestSize will throw IOException if request is rejected
-                    checkRequestSizeWhenMessageReceived(length);
-                    si.setLargeRequestSize(length);
-                }
-                si.setOwner(ServerCnxn.me);
-                submitRequest(si);
-            }
-        }
-    }
-
-    private static boolean isSaslSuperUser(String id) {
-        if (id == null || id.isEmpty()) {
-            return false;
-        }
-
-        Properties properties = System.getProperties();
-        int prefixLen = SASL_SUPER_USER.length();
-
-        for (String k : properties.stringPropertyNames()) {
-            if (k.startsWith(SASL_SUPER_USER)
-                && (k.length() == prefixLen || k.charAt(prefixLen) == '.')) {
-                String value = properties.getProperty(k);
-
-                if (value != null && value.equals(id)) {
-                    return true;
-                }
-            }
-        }
-
-        return false;
-    }
-
-    private static boolean shouldAllowSaslFailedClientsConnect() {
-        return Boolean.getBoolean(ALLOW_SASL_FAILED_CLIENTS);
-    }
-
-    private void processSasl(RequestRecord request, ServerCnxn cnxn, RequestHeader requestHeader) throws IOException {
-        LOG.debug("Responding to client SASL token.");
-        GetSASLRequest clientTokenRecord = request.readRecord(GetSASLRequest::new);
-        byte[] clientToken = clientTokenRecord.getToken();
-        LOG.debug("Size of client SASL token: {}", clientToken.length);
-        byte[] responseToken = null;
-        try {
-            ZooKeeperSaslServer saslServer = cnxn.zooKeeperSaslServer;
-            try {
-                // note that clientToken might be empty (clientToken.length == 0):
-                // if using the DIGEST-MD5 mechanism, clientToken will be empty at the beginning of the
-                // SASL negotiation process.
-                responseToken = saslServer.evaluateResponse(clientToken);
-                if (saslServer.isComplete()) {
-                    String authorizationID = saslServer.getAuthorizationID();
-                    LOG.info("Session 0x{}: adding SASL authorization for authorizationID: {}",
-                            Long.toHexString(cnxn.getSessionId()), authorizationID);
-                    cnxn.addAuthInfo(new Id("sasl", authorizationID));
-
-                    if (isSaslSuperUser(authorizationID)) {
-                        cnxn.addAuthInfo(new Id("super", ""));
-                        LOG.info(
-                            "Session 0x{}: Authenticated Id '{}' as super user",
-                            Long.toHexString(cnxn.getSessionId()),
-                            authorizationID);
-                    }
-                }
-            } catch (SaslException e) {
-                LOG.warn("Client {} failed to SASL authenticate: {}", cnxn.getRemoteSocketAddress(), e);
-                if (shouldAllowSaslFailedClientsConnect() && !authHelper.isSaslAuthRequired()) {
-                    LOG.warn("Maintaining client connection despite SASL authentication failure.");
-                } else {
-                    int error;
-                    if (authHelper.isSaslAuthRequired()) {
-                        LOG.warn(
-                            "Closing client connection due to server requires client SASL authenticaiton,"
-                                + "but client SASL authentication has failed, or client is not configured with SASL "
-                                + "authentication.");
-                        error = Code.SESSIONCLOSEDREQUIRESASLAUTH.intValue();
-                    } else {
-                        LOG.warn("Closing client connection due to SASL authentication failure.");
-                        error = Code.AUTHFAILED.intValue();
-                    }
-
-                    ReplyHeader replyHeader = new ReplyHeader(requestHeader.getXid(), 0, error);
-                    cnxn.sendResponse(replyHeader, new SetSASLResponse(null), "response");
-                    cnxn.sendCloseSession();
-                    cnxn.disableRecv();
-                    return;
-                }
-            }
-        } catch (NullPointerException e) {
-            LOG.error("cnxn.saslServer is null: cnxn object did not initialize its saslServer properly.");
-        }
-        if (responseToken != null) {
-            LOG.debug("Size of server SASL response: {}", responseToken.length);
-        }
-
-        ReplyHeader replyHeader = new ReplyHeader(requestHeader.getXid(), 0, Code.OK.intValue());
-        Record record = new SetSASLResponse(responseToken);
-        cnxn.sendResponse(replyHeader, record, "response");
-    }
-
-    // entry point for quorum/Learner.java
-    public ProcessTxnResult processTxn(TxnHeader hdr, Record txn) {
-        processTxnForSessionEvents(null, hdr, txn);
-        return processTxnInDB(hdr, txn, null);
-    }
-
-    // entry point for FinalRequestProcessor.java
-    public ProcessTxnResult processTxn(Request request) {
-        TxnHeader hdr = request.getHdr();
-        processTxnForSessionEvents(request, hdr, request.getTxn());
-
-        final boolean writeRequest = (hdr != null);
-        final boolean quorumRequest = request.isQuorum();
-
-        // return fast w/o synchronization when we get a read
-        if (!writeRequest && !quorumRequest) {
-            return new ProcessTxnResult();
-        }
-        synchronized (outstandingChanges) {
-            ProcessTxnResult rc = processTxnInDB(hdr, request.getTxn(), request.getTxnDigest());
-
-            // request.hdr is set for write requests, which are the only ones
-            // that add to outstandingChanges.
-            if (writeRequest) {
-                long zxid = hdr.getZxid();
-                while (!outstandingChanges.isEmpty()
-                        && outstandingChanges.peek().zxid <= zxid) {
-                    ChangeRecord cr = outstandingChanges.remove();
-                    ServerMetrics.getMetrics().OUTSTANDING_CHANGES_REMOVED.add(1);
-                    if (cr.zxid < zxid) {
-                        LOG.warn(
-                            "Zxid outstanding 0x{} is less than current 0x{}",
-                            Long.toHexString(cr.zxid),
-                            Long.toHexString(zxid));
-                    }
-                    if (outstandingChangesForPath.get(cr.path) == cr) {
-                        outstandingChangesForPath.remove(cr.path);
-                    }
-                }
-            }
-
-            // do not add non quorum packets to the queue.
-            if (quorumRequest) {
-                getZKDatabase().addCommittedProposal(request);
-            }
-            return rc;
-        }
-    }
-
-    private void processTxnForSessionEvents(Request request, TxnHeader hdr, Record txn) {
-        int opCode = (request == null) ? hdr.getType() : request.type;
-        long sessionId = (request == null) ? hdr.getClientId() : request.sessionId;
-
-        if (opCode == OpCode.createSession) {
-            if (hdr != null && txn instanceof CreateSessionTxn) {
-                CreateSessionTxn cst = (CreateSessionTxn) txn;
-                sessionTracker.commitSession(sessionId, cst.getTimeOut());
-            } else if (request == null || !request.isLocalSession()) {
-                LOG.warn("*****>>>>> Got {} {}",  txn.getClass(), txn.toString());
-            }
-        } else if (opCode == OpCode.closeSession) {
-            sessionTracker.removeSession(sessionId);
-        }
-    }
-
-    private ProcessTxnResult processTxnInDB(TxnHeader hdr, Record txn, TxnDigest digest) {
-        if (hdr == null) {
-            return new ProcessTxnResult();
-        } else {
-            return getZKDatabase().processTxn(hdr, txn, digest);
-        }
-    }
-
-    public Map<Long, Set<Long>> getSessionExpiryMap() {
-        return sessionTracker.getSessionExpiryMap();
-    }
-
-    /**
-     * This method is used to register the ZooKeeperServerShutdownHandler to get
-     * server's error or shutdown state change notifications.
-     * {@link ZooKeeperServerShutdownHandler#handle(State)} will be called for
-     * every server state changes {@link #setState(State)}.
-     *
-     * @param zkShutdownHandler shutdown handler
-     */
-    void registerServerShutdownHandler(ZooKeeperServerShutdownHandler zkShutdownHandler) {
-        this.zkShutdownHandler = zkShutdownHandler;
-    }
-
-    public boolean isResponseCachingEnabled() {
-        return isResponseCachingEnabled;
-    }
-
-    public void setResponseCachingEnabled(boolean isEnabled) {
-        isResponseCachingEnabled = isEnabled;
-    }
-
-    public ResponseCache getReadResponseCache() {
-        return isResponseCachingEnabled ? readResponseCache : null;
-    }
-
-    public ResponseCache getGetChildrenResponseCache() {
-        return isResponseCachingEnabled ? getChildrenResponseCache : null;
-    }
-
-    protected void registerMetrics() {
-        MetricsContext rootContext = ServerMetrics.getMetrics().getMetricsProvider().getRootContext();
-
-        final ZKDatabase zkdb = this.getZKDatabase();
-        final ServerStats stats = this.serverStats();
-
-        rootContext.registerGauge("avg_latency", stats::getAvgLatency);
-
-        rootContext.registerGauge("max_latency", stats::getMaxLatency);
-        rootContext.registerGauge("min_latency", stats::getMinLatency);
-
-        rootContext.registerGauge("packets_received", stats::getPacketsReceived);
-        rootContext.registerGauge("packets_sent", stats::getPacketsSent);
-        rootContext.registerGauge("num_alive_connections", stats::getNumAliveClientConnections);
-
-        rootContext.registerGauge("outstanding_requests", stats::getOutstandingRequests);
-        rootContext.registerGauge("uptime", stats::getUptime);
-
-        rootContext.registerGauge("znode_count", zkdb::getNodeCount);
-
-        rootContext.registerGauge("watch_count", zkdb.getDataTree()::getWatchCount);
-        rootContext.registerGauge("ephemerals_count", zkdb.getDataTree()::getEphemeralsCount);
-
-        rootContext.registerGauge("approximate_data_size", zkdb.getDataTree()::cachedApproximateDataSize);
-
-        rootContext.registerGauge("global_sessions", zkdb::getSessionCount);
-        rootContext.registerGauge("local_sessions", this.getSessionTracker()::getLocalSessionCount);
-
-        OSMXBean osMbean = new OSMXBean();
-        rootContext.registerGauge("open_file_descriptor_count", osMbean::getOpenFileDescriptorCount);
-        rootContext.registerGauge("max_file_descriptor_count", osMbean::getMaxFileDescriptorCount);
-        rootContext.registerGauge("connection_drop_probability", this::getConnectionDropChance);
-
-        rootContext.registerGauge("last_client_response_size", stats.getClientResponseStats()::getLastBufferSize);
-        rootContext.registerGauge("max_client_response_size", stats.getClientResponseStats()::getMaxBufferSize);
-        rootContext.registerGauge("min_client_response_size", stats.getClientResponseStats()::getMinBufferSize);
-
-        rootContext.registerGauge("outstanding_tls_handshake", this::getOutstandingHandshakeNum);
-        rootContext.registerGauge("auth_failed_count", stats::getAuthFailedCount);
-        rootContext.registerGauge("non_mtls_remote_conn_count", stats::getNonMTLSRemoteConnCount);
-        rootContext.registerGauge("non_mtls_local_conn_count", stats::getNonMTLSLocalConnCount);
-
-        rootContext.registerGaugeSet(QuotaMetricsUtils.QUOTA_COUNT_LIMIT_PER_NAMESPACE,
-                () -> QuotaMetricsUtils.getQuotaCountLimit(zkDb.getDataTree()));
-        rootContext.registerGaugeSet(QuotaMetricsUtils.QUOTA_BYTES_LIMIT_PER_NAMESPACE,
-                () -> QuotaMetricsUtils.getQuotaBytesLimit(zkDb.getDataTree()));
-        rootContext.registerGaugeSet(QuotaMetricsUtils.QUOTA_COUNT_USAGE_PER_NAMESPACE,
-                () -> QuotaMetricsUtils.getQuotaCountUsage(zkDb.getDataTree()));
-        rootContext.registerGaugeSet(QuotaMetricsUtils.QUOTA_BYTES_USAGE_PER_NAMESPACE,
-                () -> QuotaMetricsUtils.getQuotaBytesUsage(zkDb.getDataTree()));
-    }
-
-    protected void unregisterMetrics() {
-
-        MetricsContext rootContext = ServerMetrics.getMetrics().getMetricsProvider().getRootContext();
-
-        rootContext.unregisterGauge("avg_latency");
-
-        rootContext.unregisterGauge("max_latency");
-        rootContext.unregisterGauge("min_latency");
-
-        rootContext.unregisterGauge("packets_received");
-        rootContext.unregisterGauge("packets_sent");
-        rootContext.unregisterGauge("num_alive_connections");
-
-        rootContext.unregisterGauge("outstanding_requests");
-        rootContext.unregisterGauge("uptime");
-
-        rootContext.unregisterGauge("znode_count");
-
-        rootContext.unregisterGauge("watch_count");
-        rootContext.unregisterGauge("ephemerals_count");
-        rootContext.unregisterGauge("approximate_data_size");
-
-        rootContext.unregisterGauge("global_sessions");
-        rootContext.unregisterGauge("local_sessions");
-
-        rootContext.unregisterGauge("open_file_descriptor_count");
-        rootContext.unregisterGauge("max_file_descriptor_count");
-        rootContext.unregisterGauge("connection_drop_probability");
-
-        rootContext.unregisterGauge("last_client_response_size");
-        rootContext.unregisterGauge("max_client_response_size");
-        rootContext.unregisterGauge("min_client_response_size");
-
-        rootContext.unregisterGauge("auth_failed_count");
-        rootContext.unregisterGauge("non_mtls_remote_conn_count");
-        rootContext.unregisterGauge("non_mtls_local_conn_count");
-
-        rootContext.unregisterGaugeSet(QuotaMetricsUtils.QUOTA_COUNT_LIMIT_PER_NAMESPACE);
-        rootContext.unregisterGaugeSet(QuotaMetricsUtils.QUOTA_BYTES_LIMIT_PER_NAMESPACE);
-        rootContext.unregisterGaugeSet(QuotaMetricsUtils.QUOTA_COUNT_USAGE_PER_NAMESPACE);
-        rootContext.unregisterGaugeSet(QuotaMetricsUtils.QUOTA_BYTES_USAGE_PER_NAMESPACE);
-    }
-
-    /**
-     * Hook into admin server, useful to expose additional data
-     * that do not represent metrics.
-     *
-     * @param response a sink which collects the data.
-     */
-    public void dumpMonitorValues(BiConsumer<String, Object> response) {
-        ServerStats stats = serverStats();
-        response.accept("version", Version.getFullVersion());
-        response.accept("server_state", stats.getServerState());
-    }
-
-    /**
-     * Grant or deny authorization to an operation on a node as a function of:
-     * @param cnxn :    the server connection or null for admin server commands
-     * @param acl :     set of ACLs for the node
-     * @param perm :    the permission that the client is requesting
-     * @param ids :     the credentials supplied by the client
-     * @param path :    the ZNode path
-     * @param setAcls : for set ACL operations, the list of ACLs being set. Otherwise null.
-     */
-    public void checkACL(ServerCnxn cnxn, List<ACL> acl, int perm, List<Id> ids, String path, List<ACL> setAcls) throws KeeperException.NoAuthException {
-        if (skipACL) {
-            return;
-        }
-
-        LOG.debug("Permission requested: {} ", perm);
-        LOG.debug("ACLs for node: {}", acl);
-        LOG.debug("Client credentials: {}", ids);
-
-        if (acl == null || acl.size() == 0) {
-            return;
-        }
-        for (Id authId : ids) {
-            if (authId.getScheme().equals("super")) {
-                return;
-            }
-        }
-        for (ACL a : acl) {
-            Id id = a.getId();
-            if ((a.getPerms() & perm) != 0) {
-                if (id.getScheme().equals("world") && id.getId().equals("anyone")) {
-                    return;
-                }
-                ServerAuthenticationProvider ap = ProviderRegistry.getServerProvider(id.getScheme());
-                if (ap != null) {
-                    for (Id authId : ids) {
-                        if (authId.getScheme().equals(id.getScheme())
-                            && ap.matches(
-                                new ServerAuthenticationProvider.ServerObjs(this, cnxn),
-                                new ServerAuthenticationProvider.MatchValues(path, authId.getId(), id.getId(), perm, setAcls))) {
-                            return;
-                        }
-                    }
-                }
-            }
-        }
-        throw new KeeperException.NoAuthException();
-    }
-
-    /**
-     * check a path whether exceeded the quota.
-     *
-     * @param path
-     *            the path of the node, used for the quota prefix check
-     * @param lastData
-     *            the current node data, {@code null} for none
-     * @param data
-     *            the data to be set, or {@code null} for none
-     * @param type
-     *            currently, create and setData need to check quota
-     */
-    public void checkQuota(String path, byte[] lastData, byte[] data, int type) throws KeeperException.QuotaExceededException {
-        if (!enforceQuota) {
-            return;
-        }
-        long dataBytes = (data == null) ? 0 : data.length;
-        ZKDatabase zkDatabase = getZKDatabase();
-        String lastPrefix = zkDatabase.getDataTree().getMaxPrefixWithQuota(path);
-        if (StringUtils.isEmpty(lastPrefix)) {
-            return;
-        }
-
-        final String namespace = PathUtils.getTopNamespace(path);
-        switch (type) {
-            case OpCode.create:
-                checkQuota(lastPrefix, dataBytes, 1, namespace);
-                break;
-            case OpCode.setData:
-                checkQuota(lastPrefix, dataBytes - (lastData == null ? 0 : lastData.length), 0, namespace);
-                break;
-             default:
-                 throw new IllegalArgumentException("Unsupported OpCode for checkQuota: " + type);
-        }
-    }
-
-    /**
-     * check a path whether exceeded the quota.
-     *
-     * @param lastPrefix
-                  the path of the node which has a quota.
-     * @param bytesDiff
-     *            the diff to be added to number of bytes
-     * @param countDiff
-     *            the diff to be added to the count
-     * @param namespace
-      *           the namespace for collecting quota exceeded errors
-     */
-    private void checkQuota(String lastPrefix, long bytesDiff, long countDiff, String namespace)
-            throws KeeperException.QuotaExceededException {
-        LOG.debug("checkQuota: lastPrefix={}, bytesDiff={}, countDiff={}", lastPrefix, bytesDiff, countDiff);
-
-        // now check the quota we set
-        String limitNode = Quotas.limitPath(lastPrefix);
-        DataNode node = getZKDatabase().getNode(limitNode);
-        StatsTrack limitStats;
-        if (node == null) {
-            // should not happen
-            LOG.error("Missing limit node for quota {}", limitNode);
-            return;
-        }
-        synchronized (node) {
-            limitStats = new StatsTrack(node.data);
-        }
-        //check the quota
-        boolean checkCountQuota = countDiff != 0 && (limitStats.getCount() > -1 || limitStats.getCountHardLimit() > -1);
-        boolean checkByteQuota = bytesDiff != 0 && (limitStats.getBytes() > -1 || limitStats.getByteHardLimit() > -1);
-
-        if (!checkCountQuota && !checkByteQuota) {
-            return;
-        }
-
-        //check the statPath quota
-        String statNode = Quotas.statPath(lastPrefix);
-        node = getZKDatabase().getNode(statNode);
-
-        StatsTrack currentStats;
-        if (node == null) {
-            // should not happen
-            LOG.error("Missing node for stat {}", statNode);
-            return;
-        }
-        synchronized (node) {
-            currentStats = new StatsTrack(node.data);
-        }
-
-        //check the Count Quota
-        if (checkCountQuota) {
-            long newCount = currentStats.getCount() + countDiff;
-            boolean isCountHardLimit = limitStats.getCountHardLimit() > -1;
-            long countLimit = isCountHardLimit ? limitStats.getCountHardLimit() : limitStats.getCount();
-
-            if (newCount > countLimit) {
-                String msg = "Quota exceeded: " + lastPrefix + " [current count=" + newCount + ", " + (isCountHardLimit ? "hard" : "soft") + "CountLimit=" + countLimit + "]";
-                RATE_LOGGER.rateLimitLog(msg);
-                if (isCountHardLimit) {
-                    updateQuotaExceededMetrics(namespace);
-                    throw new KeeperException.QuotaExceededException(lastPrefix);
-                }
-            }
-        }
-
-        //check the Byte Quota
-        if (checkByteQuota) {
-            long newBytes = currentStats.getBytes() + bytesDiff;
-            boolean isByteHardLimit = limitStats.getByteHardLimit() > -1;
-            long byteLimit = isByteHardLimit ? limitStats.getByteHardLimit() : limitStats.getBytes();
-            if (newBytes > byteLimit) {
-                String msg = "Quota exceeded: " + lastPrefix + " [current bytes=" + newBytes + ", " + (isByteHardLimit ? "hard" : "soft") + "ByteLimit=" + byteLimit + "]";
-                RATE_LOGGER.rateLimitLog(msg);
-                if (isByteHardLimit) {
-                    updateQuotaExceededMetrics(namespace);
-                    throw new KeeperException.QuotaExceededException(lastPrefix);
-                }
-            }
-        }
-    }
-
-    public static boolean isDigestEnabled() {
-        return digestEnabled;
-    }
-
-    public static void setDigestEnabled(boolean digestEnabled) {
-        LOG.info("{} = {}", ZOOKEEPER_DIGEST_ENABLED, digestEnabled);
-        ZooKeeperServer.digestEnabled = digestEnabled;
-    }
-
-    public static boolean isSerializeLastProcessedZxidEnabled() {
-        return serializeLastProcessedZxidEnabled;
-    }
-
-    public static void setSerializeLastProcessedZxidEnabled(boolean serializeLastZxidEnabled) {
-        serializeLastProcessedZxidEnabled = serializeLastZxidEnabled;
-        LOG.info("{} = {}", ZOOKEEPER_SERIALIZE_LAST_PROCESSED_ZXID_ENABLED, serializeLastZxidEnabled);
-    }
-
-    /**
-     * Trim a path to get the immediate predecessor.
-     *
-     * @param path
-     * @return
-     * @throws KeeperException.BadArgumentsException
-     */
-    private String parentPath(String path) throws KeeperException.BadArgumentsException {
-        int lastSlash = path.lastIndexOf('/');
-        if (lastSlash == -1 || path.indexOf('\0') != -1 || getZKDatabase().isSpecialPath(path)) {
-            throw new KeeperException.BadArgumentsException(path);
-        }
-        return lastSlash == 0 ? "/" : path.substring(0, lastSlash);
-    }
-
-    private String effectiveACLPath(Request request) throws KeeperException.BadArgumentsException, KeeperException.InvalidACLException {
-        boolean mustCheckACL = false;
-        String path = null;
-        List<ACL> acl = null;
-
-        switch (request.type) {
-        case OpCode.create:
-        case OpCode.create2: {
-            CreateRequest req = request.readRequestRecordNoException(CreateRequest::new);
-            if (req != null) {
-                mustCheckACL = true;
-                acl = req.getAcl();
-                path = parentPath(req.getPath());
-            }
-            break;
-        }
-        case OpCode.delete: {
-            DeleteRequest req = request.readRequestRecordNoException(DeleteRequest::new);
-            if (req != null) {
-                path = parentPath(req.getPath());
-            }
-            break;
-        }
-        case OpCode.setData: {
-            SetDataRequest req = request.readRequestRecordNoException(SetDataRequest::new);
-            if (req != null) {
-                path = req.getPath();
-            }
-            break;
-        }
-        case OpCode.setACL: {
-            SetACLRequest req = request.readRequestRecordNoException(SetACLRequest::new);
-            if (req != null) {
-                mustCheckACL = true;
-                acl = req.getAcl();
-                path = req.getPath();
-            }
-            break;
-        }
-        }
-
-        if (mustCheckACL) {
-            /* we ignore the extrapolated ACL returned by fixupACL because
-             * we only care about it being well-formed (and if it isn't, an
-             * exception will be raised).
-             */
-            PrepRequestProcessor.fixupACL(path, request.authInfo, acl);
-        }
-
-        return path;
-    }
-
-    private int effectiveACLPerms(Request request) {
-        switch (request.type) {
-        case OpCode.create:
-        case OpCode.create2:
-            return ZooDefs.Perms.CREATE;
-        case OpCode.delete:
-            return ZooDefs.Perms.DELETE;
-        case OpCode.setData:
-            return ZooDefs.Perms.WRITE;
-        case OpCode.setACL:
-            return ZooDefs.Perms.ADMIN;
-        default:
-            return ZooDefs.Perms.ALL;
-        }
-    }
-
-    /**
-     * Check Write Requests for Potential Access Restrictions
-     * <p>
-     * Before a request is being proposed to the quorum, lets check it
-     * against local ACLs. Non-write requests (read, session, etc.)
-     * are passed along. Invalid requests are sent a response.
-     * <p>
-     * While we are at it, if the request will set an ACL: make sure it's
-     * a valid one.
-     *
-     * @param request
-     * @return true if request is permitted, false if not.
-     */
-    public boolean authWriteRequest(Request request) {
-        int err;
-        String pathToCheck;
-
-        if (!enableEagerACLCheck) {
-            return true;
-        }
-
-        err = KeeperException.Code.OK.intValue();
-
-        try {
-            pathToCheck = effectiveACLPath(request);
-            if (pathToCheck != null) {
-                checkACL(request.cnxn, zkDb.getACL(pathToCheck, null), effectiveACLPerms(request), request.authInfo, pathToCheck, null);
-            }
-        } catch (KeeperException.NoAuthException e) {
-            LOG.debug("Request failed ACL check", e);
-            err = e.code().intValue();
-        } catch (KeeperException.InvalidACLException e) {
-            LOG.debug("Request has an invalid ACL check", e);
-            err = e.code().intValue();
-        } catch (KeeperException.NoNodeException e) {
-            LOG.debug("ACL check against non-existent node: {}", e.getMessage());
-        } catch (KeeperException.BadArgumentsException e) {
-            LOG.debug("ACL check against illegal node path: {}", e.getMessage());
-        } catch (Throwable t) {
-            LOG.error("Uncaught exception in authWriteRequest with: ", t);
-            throw t;
-        } finally {
-            if (err != KeeperException.Code.OK.intValue()) {
-                /*  This request has a bad ACL, so we are dismissing it early. */
-                decInProcess();
-                ReplyHeader rh = new ReplyHeader(request.cxid, 0, err);
-                try {
-                    request.cnxn.sendResponse(rh, null, null);
-                } catch (IOException e) {
-                    LOG.error("IOException : {}", e);
-                }
-            }
-        }
-
-        return err == KeeperException.Code.OK.intValue();
-    }
-
-    public int getOutstandingHandshakeNum() {
-        if (serverCnxnFactory instanceof NettyServerCnxnFactory) {
-            return ((NettyServerCnxnFactory) serverCnxnFactory).getOutstandingHandshakeNum();
-        } else {
-            return 0;
-        }
-    }
-
-    public boolean isReconfigEnabled() {
-        return this.reconfigEnabled;
-    }
-
-    public ZooKeeperServerShutdownHandler getZkShutdownHandler() {
-        return zkShutdownHandler;
-    }
-
-    static void updateQuotaExceededMetrics(final String namespace) {
-        if (namespace == null) {
-            return;
-        }
-        ServerMetrics.getMetrics().QUOTA_EXCEEDED_ERROR_PER_NAMESPACE.add(namespace, 1);
-    }
-}
-
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/LeaderZooKeeperServer.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/LeaderZooKeeperServer.java
deleted file mode 100644
index 1f629bed73d..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/LeaderZooKeeperServer.java
+++ /dev/null
@@ -1,309 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.zookeeper.server.quorum;
-
-import java.io.IOException;
-import java.util.concurrent.TimeUnit;
-import java.util.function.Function;
-import javax.management.JMException;
-import org.apache.zookeeper.KeeperException.SessionExpiredException;
-import org.apache.zookeeper.jmx.MBeanRegistry;
-import org.apache.zookeeper.metrics.MetricsContext;
-import org.apache.zookeeper.server.ContainerManager;
-import org.apache.zookeeper.server.DataTreeBean;
-import org.apache.zookeeper.server.FinalRequestProcessor;
-import org.apache.zookeeper.server.PrepRequestProcessor;
-import org.apache.zookeeper.server.Request;
-import org.apache.zookeeper.server.RequestProcessor;
-import org.apache.zookeeper.server.ServerCnxn;
-import org.apache.zookeeper.server.ServerMetrics;
-import org.apache.zookeeper.server.ZKDatabase;
-import org.apache.zookeeper.server.persistence.FileTxnSnapLog;
-
-/**
- *
- * Just like the standard ZooKeeperServer. We just replace the request
- * processors: PrepRequestProcessor -&gt; ProposalRequestProcessor -&gt;
- * CommitProcessor -&gt; Leader.ToBeAppliedRequestProcessor -&gt;
- * FinalRequestProcessor
- */
-public class LeaderZooKeeperServer extends QuorumZooKeeperServer {
-
-    private ContainerManager containerManager;  // guarded by sync
-
-    CommitProcessor commitProcessor;
-
-    PrepRequestProcessor prepRequestProcessor;
-
-    /**
-     * @throws IOException
-     */
-    public LeaderZooKeeperServer(FileTxnSnapLog logFactory, QuorumPeer self, ZKDatabase zkDb) throws IOException {
-        super(logFactory, self.tickTime, self.minSessionTimeout, self.maxSessionTimeout, self.clientPortListenBacklog, zkDb, self);
-    }
-
-    public Leader getLeader() {
-        return self.leader;
-    }
-
-    @Override
-    protected void setupRequestProcessors() {
-        RequestProcessor finalProcessor = new FinalRequestProcessor(this);
-        RequestProcessor toBeAppliedProcessor = new Leader.ToBeAppliedRequestProcessor(finalProcessor, getLeader());
-        commitProcessor = new CommitProcessor(toBeAppliedProcessor, Long.toString(getServerId()), false, getZooKeeperServerListener());
-        commitProcessor.start();
-        ProposalRequestProcessor proposalProcessor = new ProposalRequestProcessor(this, commitProcessor);
-        proposalProcessor.initialize();
-        prepRequestProcessor = new PrepRequestProcessor(this, proposalProcessor);
-        prepRequestProcessor.start();
-        firstProcessor = new LeaderRequestProcessor(this, prepRequestProcessor);
-
-        setupContainerManager();
-    }
-
-    private synchronized void setupContainerManager() {
-        containerManager = new ContainerManager(
-            getZKDatabase(),
-            prepRequestProcessor,
-            Integer.getInteger("znode.container.checkIntervalMs", (int) TimeUnit.MINUTES.toMillis(1)),
-            Integer.getInteger("znode.container.maxPerMinute", 10000),
-            Long.getLong("znode.container.maxNeverUsedIntervalMs", 0)
-        );
-    }
-
-    @Override
-    public synchronized void startup() {
-        super.startup();
-        if (containerManager != null) {
-            containerManager.start();
-        }
-    }
-
-    @Override
-    protected void registerMetrics() {
-        super.registerMetrics();
-
-        MetricsContext rootContext = ServerMetrics.getMetrics().getMetricsProvider().getRootContext();
-        rootContext.registerGauge("learners", gaugeWithLeader(
-                (leader) -> leader.getLearners().size())
-        );
-        rootContext.registerGauge("synced_followers", gaugeWithLeader(
-                (leader) -> leader.getForwardingFollowers().size()
-        ));
-        rootContext.registerGauge("synced_non_voting_followers", gaugeWithLeader(
-                (leader) -> leader.getNonVotingFollowers().size()
-        ));
-        rootContext.registerGauge("synced_observers", self::getSynced_observers_metric);
-        rootContext.registerGauge("pending_syncs", gaugeWithLeader(
-                (leader) -> leader.getNumPendingSyncs()
-        ));
-        rootContext.registerGauge("leader_uptime", gaugeWithLeader(
-                (leader) -> leader.getUptime()
-        ));
-        rootContext.registerGauge("last_proposal_size", gaugeWithLeader(
-                (leader) -> leader.getProposalStats().getLastBufferSize()
-        ));
-        rootContext.registerGauge("max_proposal_size", gaugeWithLeader(
-                (leader) -> leader.getProposalStats().getMaxBufferSize()
-        ));
-        rootContext.registerGauge("min_proposal_size", gaugeWithLeader(
-                (leader) -> leader.getProposalStats().getMinBufferSize()
-        ));
-    }
-
-    private org.apache.zookeeper.metrics.Gauge gaugeWithLeader(Function<Leader, Number> supplier) {
-        return () -> {
-            final Leader leader = getLeader();
-            if (leader == null) {
-                return null;
-            }
-            return supplier.apply(leader);
-        };
-    }
-
-    @Override
-    protected void unregisterMetrics() {
-        super.unregisterMetrics();
-
-        MetricsContext rootContext = ServerMetrics.getMetrics().getMetricsProvider().getRootContext();
-        rootContext.unregisterGauge("learners");
-        rootContext.unregisterGauge("synced_followers");
-        rootContext.unregisterGauge("synced_non_voting_followers");
-        rootContext.unregisterGauge("synced_observers");
-        rootContext.unregisterGauge("pending_syncs");
-        rootContext.unregisterGauge("leader_uptime");
-
-        rootContext.unregisterGauge("last_proposal_size");
-        rootContext.unregisterGauge("max_proposal_size");
-        rootContext.unregisterGauge("min_proposal_size");
-    }
-
-    @Override
-    public synchronized void shutdown(boolean fullyShutDown) {
-        if (containerManager != null) {
-            containerManager.stop();
-        }
-        super.shutdown(fullyShutDown);
-    }
-
-    @Override
-    public int getGlobalOutstandingLimit() {
-        int divisor = self.getQuorumSize() > 2 ? self.getQuorumSize() - 1 : 1;
-        int globalOutstandingLimit = super.getGlobalOutstandingLimit() / divisor;
-        return globalOutstandingLimit;
-    }
-
-    @Override
-    public void createSessionTracker() {
-        sessionTracker = new LeaderSessionTracker(
-            this,
-            getZKDatabase().getSessionWithTimeOuts(),
-            tickTime,
-            self.getMyId(),
-            self.areLocalSessionsEnabled(),
-            getZooKeeperServerListener());
-    }
-
-    public boolean touch(long sess, int to) {
-        return sessionTracker.touchSession(sess, to);
-    }
-
-    public boolean checkIfValidGlobalSession(long sess, int to) {
-        if (self.areLocalSessionsEnabled() && !upgradeableSessionTracker.isGlobalSession(sess)) {
-            return false;
-        }
-        return sessionTracker.touchSession(sess, to);
-    }
-
-    /**
-     * Requests coming from the learner should go directly to
-     * PrepRequestProcessor
-     *
-     * @param request
-     */
-    public void submitLearnerRequest(Request request) {
-        /*
-         * Requests coming from the learner should have gone through
-         * submitRequest() on each server which already perform some request
-         * validation, so we don't need to do it again.
-         *
-         * Additionally, LearnerHandler should start submitting requests into
-         * the leader's pipeline only when the leader's server is started, so we
-         * can submit the request directly into PrepRequestProcessor.
-         *
-         * This is done so that requests from learners won't go through
-         * LeaderRequestProcessor which perform local session upgrade.
-         */
-        prepRequestProcessor.processRequest(request);
-    }
-
-    @Override
-    protected void registerJMX() {
-        // register with JMX
-        try {
-            jmxDataTreeBean = new DataTreeBean(getZKDatabase().getDataTree());
-            MBeanRegistry.getInstance().register(jmxDataTreeBean, jmxServerBean);
-        } catch (Exception e) {
-            LOG.warn("Failed to register with JMX", e);
-            jmxDataTreeBean = null;
-        }
-    }
-
-    public void registerJMX(LeaderBean leaderBean, LocalPeerBean localPeerBean) {
-        // register with JMX
-        if (self.jmxLeaderElectionBean != null) {
-            try {
-                MBeanRegistry.getInstance().unregister(self.jmxLeaderElectionBean);
-            } catch (Exception e) {
-                LOG.warn("Failed to register with JMX", e);
-            }
-            self.jmxLeaderElectionBean = null;
-        }
-
-        try {
-            jmxServerBean = leaderBean;
-            MBeanRegistry.getInstance().register(leaderBean, localPeerBean);
-        } catch (Exception e) {
-            LOG.warn("Failed to register with JMX", e);
-            jmxServerBean = null;
-        }
-    }
-
-    boolean registerJMX(LearnerHandlerBean handlerBean) {
-        try {
-            MBeanRegistry.getInstance().register(handlerBean, jmxServerBean);
-            return true;
-        } catch (JMException e) {
-            LOG.warn("Could not register connection", e);
-        }
-        return false;
-    }
-
-    @Override
-    protected void unregisterJMX() {
-        // unregister from JMX
-        try {
-            if (jmxDataTreeBean != null) {
-                MBeanRegistry.getInstance().unregister(jmxDataTreeBean);
-            }
-        } catch (Exception e) {
-            LOG.warn("Failed to unregister with JMX", e);
-        }
-        jmxDataTreeBean = null;
-    }
-
-    protected void unregisterJMX(Leader leader) {
-        // unregister from JMX
-        try {
-            if (jmxServerBean != null) {
-                MBeanRegistry.getInstance().unregister(jmxServerBean);
-            }
-        } catch (Exception e) {
-            LOG.warn("Failed to unregister with JMX", e);
-        }
-        jmxServerBean = null;
-    }
-
-    @Override
-    public String getState() {
-        return "leader";
-    }
-
-    /**
-     * Returns the id of the associated QuorumPeer, which will do for a unique
-     * id of this server.
-     */
-    @Override
-    public long getServerId() {
-        return self.getMyId();
-    }
-
-    @Override
-    protected void revalidateSession(ServerCnxn cnxn, long sessionId, int sessionTimeout) throws IOException {
-        super.revalidateSession(cnxn, sessionId, sessionTimeout);
-        try {
-            // setowner as the leader itself, unless updated
-            // via the follower handlers
-            setOwner(sessionId, ServerCnxn.me);
-        } catch (SessionExpiredException e) {
-            // this is ok, it just means that the session revalidation failed.
-        }
-    }
-
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/Learner.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/Learner.java
deleted file mode 100644
index 3c7b2148400..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/Learner.java
+++ /dev/null
@@ -1,928 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.zookeeper.server.quorum;
-
-import static java.nio.charset.StandardCharsets.UTF_8;
-import java.io.BufferedInputStream;
-import java.io.BufferedOutputStream;
-import java.io.ByteArrayInputStream;
-import java.io.ByteArrayOutputStream;
-import java.io.DataInputStream;
-import java.io.DataOutputStream;
-import java.io.IOException;
-import java.net.InetSocketAddress;
-import java.net.Socket;
-import java.nio.ByteBuffer;
-import java.util.ArrayDeque;
-import java.util.Deque;
-import java.util.Map;
-import java.util.Map.Entry;
-import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicReference;
-import javax.net.ssl.SSLSocket;
-import org.apache.jute.BinaryInputArchive;
-import org.apache.jute.BinaryOutputArchive;
-import org.apache.jute.InputArchive;
-import org.apache.jute.OutputArchive;
-import org.apache.jute.Record;
-import org.apache.zookeeper.ZooDefs.OpCode;
-import org.apache.zookeeper.common.Time;
-import org.apache.zookeeper.common.X509Exception;
-import org.apache.zookeeper.server.ExitCode;
-import org.apache.zookeeper.server.Request;
-import org.apache.zookeeper.server.ServerCnxn;
-import org.apache.zookeeper.server.ServerMetrics;
-import org.apache.zookeeper.server.TxnLogEntry;
-import org.apache.zookeeper.server.ZooTrace;
-import org.apache.zookeeper.server.quorum.QuorumPeer.QuorumServer;
-import org.apache.zookeeper.server.quorum.flexible.QuorumVerifier;
-import org.apache.zookeeper.server.util.ConfigUtils;
-import org.apache.zookeeper.server.util.MessageTracker;
-import org.apache.zookeeper.server.util.SerializeUtils;
-import org.apache.zookeeper.server.util.ZxidUtils;
-import org.apache.zookeeper.txn.SetDataTxn;
-import org.apache.zookeeper.txn.TxnDigest;
-import org.apache.zookeeper.txn.TxnHeader;
-import org.apache.zookeeper.util.ServiceUtils;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-/**
- * This class is the superclass of two of the three main actors in a ZK
- * ensemble: Followers and Observers. Both Followers and Observers share
- * a good deal of code which is moved into Peer to avoid duplication.
- */
-public class Learner {
-
-    static class PacketInFlight {
-
-        TxnHeader hdr;
-        Record rec;
-        TxnDigest digest;
-
-    }
-
-    QuorumPeer self;
-    LearnerZooKeeperServer zk;
-
-    protected BufferedOutputStream bufferedOutput;
-
-    protected Socket sock;
-    protected MultipleAddresses leaderAddr;
-    protected AtomicBoolean sockBeingClosed = new AtomicBoolean(false);
-
-    /**
-     * Socket getter
-     */
-    public Socket getSocket() {
-        return sock;
-    }
-
-    LearnerSender sender = null;
-    protected InputArchive leaderIs;
-    protected OutputArchive leaderOs;
-    /** the protocol version of the leader */
-    protected int leaderProtocolVersion = 0x01;
-
-    private static final int BUFFERED_MESSAGE_SIZE = 10;
-    protected final MessageTracker messageTracker = new MessageTracker(BUFFERED_MESSAGE_SIZE);
-
-    protected static final Logger LOG = LoggerFactory.getLogger(Learner.class);
-
-    /**
-     * Time to wait after connection attempt with the Leader or LearnerMaster before this
-     * Learner tries to connect again.
-     */
-    private static final int leaderConnectDelayDuringRetryMs = Integer.getInteger("zookeeper.leaderConnectDelayDuringRetryMs", 100);
-
-    private static final boolean nodelay = System.getProperty("follower.nodelay", "true").equals("true");
-
-    public static final String LEARNER_ASYNC_SENDING = "zookeeper.learner.asyncSending";
-    private static boolean asyncSending =
-        Boolean.parseBoolean(ConfigUtils.getPropertyBackwardCompatibleWay(LEARNER_ASYNC_SENDING));
-    public static final String LEARNER_CLOSE_SOCKET_ASYNC = "zookeeper.learner.closeSocketAsync";
-    public static final boolean closeSocketAsync = Boolean
-        .parseBoolean(ConfigUtils.getPropertyBackwardCompatibleWay(LEARNER_CLOSE_SOCKET_ASYNC));
-
-    static {
-        LOG.info("leaderConnectDelayDuringRetryMs: {}", leaderConnectDelayDuringRetryMs);
-        LOG.info("TCP NoDelay set to: {}", nodelay);
-        LOG.info("{} = {}", LEARNER_ASYNC_SENDING, asyncSending);
-        LOG.info("{} = {}", LEARNER_CLOSE_SOCKET_ASYNC, closeSocketAsync);
-    }
-
-    final ConcurrentHashMap<Long, ServerCnxn> pendingRevalidations = new ConcurrentHashMap<>();
-
-    public int getPendingRevalidationsCount() {
-        return pendingRevalidations.size();
-    }
-
-    // for testing
-    protected static void setAsyncSending(boolean newMode) {
-        asyncSending = newMode;
-        LOG.info("{} = {}", LEARNER_ASYNC_SENDING, asyncSending);
-
-    }
-    protected static boolean getAsyncSending() {
-        return asyncSending;
-    }
-    /**
-     * validate a session for a client
-     *
-     * @param clientId
-     *                the client to be revalidated
-     * @param timeout
-     *                the timeout for which the session is valid
-     * @throws IOException
-     */
-    void validateSession(ServerCnxn cnxn, long clientId, int timeout) throws IOException {
-        LOG.info("Revalidating client: 0x{}", Long.toHexString(clientId));
-        ByteArrayOutputStream baos = new ByteArrayOutputStream();
-        DataOutputStream dos = new DataOutputStream(baos);
-        dos.writeLong(clientId);
-        dos.writeInt(timeout);
-        dos.close();
-        QuorumPacket qp = new QuorumPacket(Leader.REVALIDATE, -1, baos.toByteArray(), null);
-        pendingRevalidations.put(clientId, cnxn);
-        if (LOG.isTraceEnabled()) {
-            ZooTrace.logTraceMessage(
-                LOG,
-                ZooTrace.SESSION_TRACE_MASK,
-                "To validate session 0x" + Long.toHexString(clientId));
-        }
-        writePacket(qp, true);
-    }
-
-    /**
-     * write a packet to the leader.
-     *
-     * This method is called by multiple threads. We need to make sure that only one thread is writing to leaderOs at a time.
-     * When packets are sent synchronously, writing is done within a synchronization block.
-     * When packets are sent asynchronously, sender.queuePacket() is called, which writes to a BlockingQueue, which is thread-safe.
-     * Reading from this BlockingQueue and writing to leaderOs is the learner sender thread only.
-     * So we have only one thread writing to leaderOs at a time in either case.
-     *
-     * @param pp
-     *                the proposal packet to be sent to the leader
-     * @throws IOException
-     */
-    void writePacket(QuorumPacket pp, boolean flush) throws IOException {
-        if (asyncSending) {
-            sender.queuePacket(pp);
-        } else {
-            writePacketNow(pp, flush);
-        }
-    }
-
-    void writePacketNow(QuorumPacket pp, boolean flush) throws IOException {
-        synchronized (leaderOs) {
-            if (pp != null) {
-                messageTracker.trackSent(pp.getType());
-                leaderOs.writeRecord(pp, "packet");
-            }
-            if (flush) {
-                bufferedOutput.flush();
-            }
-        }
-    }
-
-    /**
-     * Start thread that will forward any packet in the queue to the leader
-     */
-    protected void startSendingThread() {
-        sender = new LearnerSender(this);
-        sender.start();
-    }
-
-    /**
-     * read a packet from the leader
-     *
-     * @param pp
-     *                the packet to be instantiated
-     * @throws IOException
-     */
-    void readPacket(QuorumPacket pp) throws IOException {
-        synchronized (leaderIs) {
-            leaderIs.readRecord(pp, "packet");
-            messageTracker.trackReceived(pp.getType());
-        }
-        if (LOG.isTraceEnabled()) {
-            final long traceMask =
-                (pp.getType() == Leader.PING) ? ZooTrace.SERVER_PING_TRACE_MASK
-                    : ZooTrace.SERVER_PACKET_TRACE_MASK;
-
-            ZooTrace.logQuorumPacket(LOG, traceMask, 'i', pp);
-        }
-    }
-
-    /**
-     * send a request packet to the leader
-     *
-     * @param request
-     *                the request from the client
-     * @throws IOException
-     */
-    void request(Request request) throws IOException {
-        if (request.isThrottled()) {
-            LOG.error("Throttled request sent to leader: {}. Exiting", request);
-            ServiceUtils.requestSystemExit(ExitCode.UNEXPECTED_ERROR.getValue());
-        }
-        ByteArrayOutputStream baos = new ByteArrayOutputStream();
-        DataOutputStream oa = new DataOutputStream(baos);
-        oa.writeLong(request.sessionId);
-        oa.writeInt(request.cxid);
-        oa.writeInt(request.type);
-        byte[] payload = request.readRequestBytes();
-        if (payload != null) {
-            oa.write(payload);
-        }
-        oa.close();
-        QuorumPacket qp = new QuorumPacket(Leader.REQUEST, -1, baos.toByteArray(), request.authInfo);
-        writePacket(qp, true);
-    }
-
-    /**
-     * Returns the address of the node we think is the leader.
-     */
-    protected QuorumServer findLeader() {
-        QuorumServer leaderServer = null;
-        // Find the leader by id
-        Vote current = self.getCurrentVote();
-        for (QuorumServer s : self.getView().values()) {
-            if (s.id == current.getId()) {
-                // Ensure we have the leader's correct IP address before
-                // attempting to connect.
-                s.recreateSocketAddresses();
-                leaderServer = s;
-                break;
-            }
-        }
-        if (leaderServer == null) {
-            LOG.warn("Couldn't find the leader with id = {}", current.getId());
-        }
-        return leaderServer;
-    }
-
-    /**
-     * Overridable helper method to return the System.nanoTime().
-     * This method behaves identical to System.nanoTime().
-     */
-    protected long nanoTime() {
-        return System.nanoTime();
-    }
-
-    /**
-     * Overridable helper method to simply call sock.connect(). This can be
-     * overriden in tests to fake connection success/failure for connectToLeader.
-     */
-    protected void sockConnect(Socket sock, InetSocketAddress addr, int timeout) throws IOException {
-        sock.connect(addr, timeout);
-    }
-
-    /**
-     * Establish a connection with the LearnerMaster found by findLearnerMaster.
-     * Followers only connect to Leaders, Observers can connect to any active LearnerMaster.
-     * Retries until either initLimit time has elapsed or 5 tries have happened.
-     * @param multiAddr - the address of the Peer to connect to.
-     * @throws IOException - if the socket connection fails on the 5th attempt
-     * if there is an authentication failure while connecting to leader
-     */
-    protected void connectToLeader(MultipleAddresses multiAddr, String hostname) throws IOException {
-
-        this.leaderAddr = multiAddr;
-        Set<InetSocketAddress> addresses;
-        if (self.isMultiAddressReachabilityCheckEnabled()) {
-            // even if none of the addresses are reachable, we want to try to establish connection
-            // see ZOOKEEPER-3758
-            addresses = multiAddr.getAllReachableAddressesOrAll();
-        } else {
-            addresses = multiAddr.getAllAddresses();
-        }
-        ExecutorService executor = Executors.newFixedThreadPool(addresses.size());
-        CountDownLatch latch = new CountDownLatch(addresses.size());
-        AtomicReference<Socket> socket = new AtomicReference<>(null);
-        addresses.stream().map(address -> new LeaderConnector(address, socket, latch)).forEach(executor::submit);
-
-        try {
-            latch.await();
-        } catch (InterruptedException e) {
-            LOG.warn("Interrupted while trying to connect to Leader", e);
-        } finally {
-            executor.shutdown();
-            try {
-                if (!executor.awaitTermination(1, TimeUnit.SECONDS)) {
-                    LOG.error("not all the LeaderConnector terminated properly");
-                }
-            } catch (InterruptedException ie) {
-                LOG.error("Interrupted while terminating LeaderConnector executor.", ie);
-            }
-        }
-
-        if (socket.get() == null) {
-            throw new IOException("Failed connect to " + multiAddr);
-        } else {
-            sock = socket.get();
-            sockBeingClosed.set(false);
-        }
-
-        self.authLearner.authenticate(sock, hostname);
-
-        leaderIs = BinaryInputArchive.getArchive(new BufferedInputStream(sock.getInputStream()));
-        bufferedOutput = new BufferedOutputStream(sock.getOutputStream());
-        leaderOs = BinaryOutputArchive.getArchive(bufferedOutput);
-        if (asyncSending) {
-            startSendingThread();
-        }
-    }
-
-    class LeaderConnector implements Runnable {
-
-        private AtomicReference<Socket> socket;
-        private InetSocketAddress address;
-        private CountDownLatch latch;
-
-        LeaderConnector(InetSocketAddress address, AtomicReference<Socket> socket, CountDownLatch latch) {
-            this.address = address;
-            this.socket = socket;
-            this.latch = latch;
-        }
-
-        @Override
-        public void run() {
-            try {
-                Thread.currentThread().setName("LeaderConnector-" + address);
-                Socket sock = connectToLeader();
-
-                if (sock != null && sock.isConnected()) {
-                    if (socket.compareAndSet(null, sock)) {
-                        LOG.info("Successfully connected to leader, using address: {}", address);
-                    } else {
-                        LOG.info("Connection to the leader is already established, close the redundant connection");
-                        sock.close();
-                    }
-                }
-
-            } catch (Exception e) {
-                LOG.error("Failed connect to {}", address, e);
-            } finally {
-                latch.countDown();
-            }
-        }
-
-        private Socket connectToLeader() throws IOException, X509Exception, InterruptedException {
-            Socket sock = createSocket();
-
-            // leader connection timeout defaults to tickTime * initLimit
-            int connectTimeout = self.tickTime * self.initLimit;
-
-            // but if connectToLearnerMasterLimit is specified, use that value to calculate
-            // timeout instead of using the initLimit value
-            if (self.connectToLearnerMasterLimit > 0) {
-                connectTimeout = self.tickTime * self.connectToLearnerMasterLimit;
-            }
-
-            int remainingTimeout;
-            long startNanoTime = nanoTime();
-
-            for (int tries = 0; tries < 5 && socket.get() == null; tries++) {
-                try {
-                    // recalculate the init limit time because retries sleep for 1000 milliseconds
-                    remainingTimeout = connectTimeout - (int) ((nanoTime() - startNanoTime) / 1_000_000);
-                    if (remainingTimeout <= 0) {
-                        LOG.error("connectToLeader exceeded on retries.");
-                        throw new IOException("connectToLeader exceeded on retries.");
-                    }
-
-                    sockConnect(sock, address, Math.min(connectTimeout, remainingTimeout));
-                    if (self.isSslQuorum()) {
-                        ((SSLSocket) sock).startHandshake();
-                    }
-                    sock.setTcpNoDelay(nodelay);
-                    break;
-                } catch (IOException e) {
-                    remainingTimeout = connectTimeout - (int) ((nanoTime() - startNanoTime) / 1_000_000);
-
-                    if (remainingTimeout <= leaderConnectDelayDuringRetryMs) {
-                        LOG.error(
-                          "Unexpected exception, connectToLeader exceeded. tries={}, remaining init limit={}, connecting to {}",
-                          tries,
-                          remainingTimeout,
-                          address,
-                          e);
-                        throw e;
-                    } else if (tries >= 4) {
-                        LOG.error(
-                          "Unexpected exception, retries exceeded. tries={}, remaining init limit={}, connecting to {}",
-                          tries,
-                          remainingTimeout,
-                          address,
-                          e);
-                        throw e;
-                    } else {
-                        LOG.warn(
-                          "Unexpected exception, tries={}, remaining init limit={}, connecting to {}",
-                          tries,
-                          remainingTimeout,
-                          address,
-                          e);
-                        sock = createSocket();
-                    }
-                }
-                Thread.sleep(leaderConnectDelayDuringRetryMs);
-            }
-
-            return sock;
-        }
-    }
-
-    /**
-     * Creating a simple or and SSL socket.
-     * This can be overridden in tests to fake already connected sockets for connectToLeader.
-     */
-    protected Socket createSocket() throws X509Exception, IOException {
-        Socket sock;
-        if (self.isSslQuorum()) {
-            sock = self.getX509Util().createSSLSocket();
-        } else {
-            sock = new Socket();
-        }
-        sock.setSoTimeout(self.tickTime * self.initLimit);
-        return sock;
-    }
-
-    /**
-     * Once connected to the leader or learner master, perform the handshake
-     * protocol to establish a following / observing connection.
-     * @param pktType
-     * @return the zxid the Leader sends for synchronization purposes.
-     * @throws IOException
-     */
-    protected long registerWithLeader(int pktType) throws IOException {
-        /*
-         * Send follower info, including last zxid and sid
-         */
-        long lastLoggedZxid = self.getLastLoggedZxid();
-        QuorumPacket qp = new QuorumPacket();
-        qp.setType(pktType);
-        qp.setZxid(ZxidUtils.makeZxid(self.getAcceptedEpoch(), 0));
-
-        /*
-         * Add sid to payload
-         */
-        LearnerInfo li = new LearnerInfo(self.getMyId(), 0x10000, self.getQuorumVerifier().getVersion());
-        ByteArrayOutputStream bsid = new ByteArrayOutputStream();
-        BinaryOutputArchive boa = BinaryOutputArchive.getArchive(bsid);
-        boa.writeRecord(li, "LearnerInfo");
-        qp.setData(bsid.toByteArray());
-
-        writePacket(qp, true);
-        readPacket(qp);
-        final long newEpoch = ZxidUtils.getEpochFromZxid(qp.getZxid());
-        if (qp.getType() == Leader.LEADERINFO) {
-            // we are connected to a 1.0 server so accept the new epoch and read the next packet
-            leaderProtocolVersion = ByteBuffer.wrap(qp.getData()).getInt();
-            byte[] epochBytes = new byte[4];
-            final ByteBuffer wrappedEpochBytes = ByteBuffer.wrap(epochBytes);
-            if (newEpoch > self.getAcceptedEpoch()) {
-                wrappedEpochBytes.putInt((int) self.getCurrentEpoch());
-                self.setAcceptedEpoch(newEpoch);
-            } else if (newEpoch == self.getAcceptedEpoch()) {
-                // since we have already acked an epoch equal to the leaders, we cannot ack
-                // again, but we still need to send our lastZxid to the leader so that we can
-                // sync with it if it does assume leadership of the epoch.
-                // the -1 indicates that this reply should not count as an ack for the new epoch
-                wrappedEpochBytes.putInt(-1);
-            } else {
-                throw new IOException("Leaders epoch, "
-                                      + newEpoch
-                                      + " is less than accepted epoch, "
-                                      + self.getAcceptedEpoch());
-            }
-            QuorumPacket ackNewEpoch = new QuorumPacket(Leader.ACKEPOCH, lastLoggedZxid, epochBytes, null);
-            writePacket(ackNewEpoch, true);
-            return ZxidUtils.makeZxid(newEpoch, 0);
-        } else {
-            if (newEpoch > self.getAcceptedEpoch()) {
-                self.setAcceptedEpoch(newEpoch);
-            }
-            if (qp.getType() != Leader.NEWLEADER) {
-                LOG.error("First packet should have been NEWLEADER");
-                throw new IOException("First packet should have been NEWLEADER");
-            }
-            return qp.getZxid();
-        }
-    }
-
-    /**
-     * Finally, synchronize our history with the Leader (if Follower)
-     * or the LearnerMaster (if Observer).
-     * @param newLeaderZxid
-     * @throws IOException
-     * @throws InterruptedException
-     */
-    protected void syncWithLeader(long newLeaderZxid) throws Exception {
-        long newEpoch = ZxidUtils.getEpochFromZxid(newLeaderZxid);
-        QuorumVerifier newLeaderQV = null;
-
-        class SyncHelper {
-
-            // In the DIFF case we don't need to do a snapshot because the transactions will sync on top of any existing snapshot.
-            // For SNAP and TRUNC the snapshot is needed to save that history.
-            boolean willSnapshot = true;
-            boolean syncSnapshot = false;
-
-            // PROPOSALs received during sync, for matching up with COMMITs.
-            Deque<PacketInFlight> proposals = new ArrayDeque<>();
-
-            // PROPOSALs we delay forwarding to the ZK server until sync is done.
-            Deque<PacketInFlight> delayedProposals = new ArrayDeque<>();
-
-            // COMMITs we delay forwarding to the ZK server until sync is done.
-            Deque<Long> delayedCommits = new ArrayDeque<>();
-
-            void syncSnapshot() {
-                syncSnapshot = true;
-            }
-
-            void noSnapshot() {
-                willSnapshot = false;
-            }
-
-            void propose(PacketInFlight pif) {
-                proposals.add(pif);
-                delayedProposals.add(pif);
-            }
-
-            PacketInFlight nextProposal() {
-                return proposals.peekFirst();
-            }
-
-            void commit() {
-                PacketInFlight packet = proposals.remove();
-                if (willSnapshot) {
-                    zk.processTxn(packet.hdr, packet.rec);
-                    delayedProposals.remove();
-                } else {
-                    delayedCommits.add(packet.hdr.getZxid());
-                }
-            }
-
-            void writeState() throws IOException, InterruptedException {
-                // Ensure all received transaction PROPOSALs are written before we ACK the NEWLEADER,
-                // since this allows the leader to apply those transactions to its served state:
-                if (willSnapshot) {
-                    zk.takeSnapshot(syncSnapshot); // either, the snapshot contains the transactions,
-                    willSnapshot = false;          // but anything after this needs to go to the transaction log; or
-                }
-
-                sock.setSoTimeout(self.tickTime * self.syncLimit);
-                self.setSyncMode(QuorumPeer.SyncMode.NONE);
-                zk.startupWithoutServing();
-
-                // if we're a follower, we need to ensure the transactions are safely logged before ACK'ing.
-                if (zk instanceof FollowerZooKeeperServer) {
-                    FollowerZooKeeperServer fzk = (FollowerZooKeeperServer) zk;
-                    // The leader expects the NEWLEADER ACK to precede all the PROPOSAL ACKs, so we only write them first.
-                    fzk.syncProcessor.setDelayForwarding(true);
-                    for (PacketInFlight p : delayedProposals) {
-                        fzk.logRequest(p.hdr, p.rec, p.digest);
-                    }
-                    delayedProposals.clear();
-                    fzk.syncProcessor.syncFlush();
-                }
-
-                self.setCurrentEpoch(newEpoch);
-            }
-
-            void flushAcks() throws InterruptedException {
-                if (zk instanceof FollowerZooKeeperServer) {
-                    // The NEWLEADER is ACK'ed, and we can now ACK the PROPOSALs we wrote in writeState.
-                    FollowerZooKeeperServer fzk = (FollowerZooKeeperServer) zk;
-                    fzk.syncProcessor.setDelayForwarding(false);
-                    fzk.syncProcessor.syncFlush(); // Ensure these are all ACK'ed before the UPTODATE ACK.
-                }
-            }
-
-            void applyDelayedPackets() {
-                // Any delayed packets must now be applied: all PROPOSALs first, then any COMMITs.
-                if (zk instanceof FollowerZooKeeperServer) {
-                    FollowerZooKeeperServer fzk = (FollowerZooKeeperServer) zk;
-                    for (PacketInFlight p : delayedProposals) {
-                        fzk.logRequest(p.hdr, p.rec, p.digest);
-                    }
-                    for (Long zxid : delayedCommits) {
-                        fzk.commit(zxid);
-                    }
-                } else if (zk instanceof ObserverZooKeeperServer) {
-                    ObserverZooKeeperServer ozk = (ObserverZooKeeperServer) zk;
-                    for (PacketInFlight p : delayedProposals) {
-                        Long zxid = delayedCommits.peekFirst();
-                        if (p.hdr.getZxid() != zxid) {
-                            // log warning message if there is no matching commit
-                            // old leader send outstanding proposal to observer
-                            LOG.warn(
-                                    "Committing 0x{}, but next proposal is 0x{}",
-                                    Long.toHexString(zxid),
-                                    Long.toHexString(p.hdr.getZxid()));
-                            continue;
-                        }
-                        delayedCommits.remove();
-                        Request request = new Request(p.hdr.getClientId(), p.hdr.getCxid(), p.hdr.getType(), p.hdr, p.rec, -1);
-                        request.setTxnDigest(p.digest);
-                        ozk.commitRequest(request);
-                    }
-                } else {
-                    // New server type need to handle in-flight packets
-                    throw new UnsupportedOperationException("Unknown server type");
-                }
-            }
-
-        }
-
-        SyncHelper helper = new SyncHelper();
-        QuorumPacket qp = new QuorumPacket();
-        readPacket(qp);
-        synchronized (zk) {
-            if (qp.getType() == Leader.DIFF) {
-                LOG.info("Getting a diff from the leader 0x{}", Long.toHexString(qp.getZxid()));
-                self.setSyncMode(QuorumPeer.SyncMode.DIFF);
-                if (zk.shouldForceWriteInitialSnapshotAfterLeaderElection()) {
-                    LOG.info("Forcing a snapshot write as part of upgrading from an older Zookeeper. This should only happen while upgrading.");
-                    helper.syncSnapshot();
-                } else {
-                    helper.noSnapshot();
-                }
-            } else if (qp.getType() == Leader.SNAP) {
-                self.setSyncMode(QuorumPeer.SyncMode.SNAP);
-                LOG.info("Getting a snapshot from leader 0x{}", Long.toHexString(qp.getZxid()));
-                // The leader is going to dump the database
-                zk.getZKDatabase().deserializeSnapshot(leaderIs);
-                // ZOOKEEPER-2819: overwrite config node content extracted
-                // from leader snapshot with local config, to avoid potential
-                // inconsistency of config node content during rolling restart.
-                if (!self.isReconfigEnabled()) {
-                    LOG.debug("Reset config node content from local config after deserialization of snapshot.");
-                    zk.getZKDatabase().initConfigInZKDatabase(self.getQuorumVerifier());
-                }
-                String signature = leaderIs.readString("signature");
-                if (!signature.equals("BenWasHere")) {
-                    LOG.error("Missing signature. Got {}", signature);
-                    throw new IOException("Missing signature");
-                }
-                zk.getZKDatabase().setlastProcessedZxid(qp.getZxid());
-
-                // Immediately persist the latest snapshot when there is txn log gap
-                helper.syncSnapshot();
-            } else if (qp.getType() == Leader.TRUNC) {
-                // We need to truncate the log to the lastZxid of the leader
-                self.setSyncMode(QuorumPeer.SyncMode.TRUNC);
-                LOG.warn("Truncating log to get in sync with the leader 0x{}", Long.toHexString(qp.getZxid()));
-                boolean truncated = zk.getZKDatabase().truncateLog(qp.getZxid());
-                if (!truncated) {
-                    LOG.error("Not able to truncate the log 0x{}", Long.toHexString(qp.getZxid()));
-                    ServiceUtils.requestSystemExit(ExitCode.QUORUM_PACKET_ERROR.getValue());
-                }
-                zk.getZKDatabase().setlastProcessedZxid(qp.getZxid());
-            } else {
-                LOG.error("Got unexpected packet from leader: {}, exiting ... ", LearnerHandler.packetToString(qp));
-                ServiceUtils.requestSystemExit(ExitCode.QUORUM_PACKET_ERROR.getValue());
-            }
-            zk.getZKDatabase().initConfigInZKDatabase(self.getQuorumVerifier());
-            zk.createSessionTracker();
-
-
-            // we are now going to start getting transactions to apply followed by an UPTODATE
-            long lastQueued = 0;
-            TxnLogEntry logEntry;
-            outerLoop:
-            while (self.isRunning()) {
-                readPacket(qp);
-                switch (qp.getType()) {
-                case Leader.PROPOSAL:
-                    PacketInFlight pif = new PacketInFlight();
-                    logEntry = SerializeUtils.deserializeTxn(qp.getData());
-                    pif.hdr = logEntry.getHeader();
-                    pif.rec = logEntry.getTxn();
-                    pif.digest = logEntry.getDigest();
-                    if (pif.hdr.getZxid() != lastQueued + 1) {
-                        LOG.warn(
-                            "Got zxid 0x{} expected 0x{}",
-                            Long.toHexString(pif.hdr.getZxid()),
-                            Long.toHexString(lastQueued + 1));
-                    }
-                    lastQueued = pif.hdr.getZxid();
-
-                    if (pif.hdr.getType() == OpCode.reconfig) {
-                        SetDataTxn setDataTxn = (SetDataTxn) pif.rec;
-                        QuorumVerifier qv = self.configFromString(new String(setDataTxn.getData(), UTF_8));
-                        self.setLastSeenQuorumVerifier(qv, true);
-                    }
-                    helper.propose(pif);
-                    break;
-                case Leader.COMMIT:
-                case Leader.COMMITANDACTIVATE:
-                    pif = helper.nextProposal();
-                    if (pif.hdr.getZxid() != qp.getZxid()) {
-                        LOG.warn(
-                            "Committing 0x{}, but next proposal is 0x{}",
-                            Long.toHexString(qp.getZxid()),
-                            Long.toHexString(pif.hdr.getZxid()));
-                    } else {
-                        if (qp.getType() == Leader.COMMITANDACTIVATE) {
-                            tryReconfig(pif, ByteBuffer.wrap(qp.getData()).getLong(), qp.getZxid());
-                        }
-                        helper.commit();
-                    }
-                    break;
-                case Leader.INFORM:
-                case Leader.INFORMANDACTIVATE:
-                    PacketInFlight packet = new PacketInFlight();
-                    if (qp.getType() == Leader.INFORMANDACTIVATE) {
-                        ByteBuffer buffer = ByteBuffer.wrap(qp.getData());
-                        long suggestedLeaderId = buffer.getLong();
-                        byte[] remainingData = new byte[buffer.remaining()];
-                        buffer.get(remainingData);
-                        logEntry = SerializeUtils.deserializeTxn(remainingData);
-                        packet.hdr = logEntry.getHeader();
-                        packet.rec = logEntry.getTxn();
-                        packet.digest = logEntry.getDigest();
-                        tryReconfig(packet, suggestedLeaderId, qp.getZxid());
-                    } else {
-                        logEntry = SerializeUtils.deserializeTxn(qp.getData());
-                        packet.rec = logEntry.getTxn();
-                        packet.hdr = logEntry.getHeader();
-                        packet.digest = logEntry.getDigest();
-                        // Log warning message if txn comes out-of-order
-                        if (packet.hdr.getZxid() != lastQueued + 1) {
-                            LOG.warn(
-                                "Got zxid 0x{} expected 0x{}",
-                                Long.toHexString(packet.hdr.getZxid()),
-                                Long.toHexString(lastQueued + 1));
-                        }
-                        lastQueued = packet.hdr.getZxid();
-                    }
-                    helper.propose(packet);
-                    helper.commit();
-                    break;
-                case Leader.UPTODATE:
-                    LOG.info("Learner received UPTODATE message");
-                    if (newLeaderQV != null) {
-                        boolean majorChange = self.processReconfig(newLeaderQV, null, null, true);
-                        if (majorChange) {
-                            throw new Exception("changes proposed in reconfig");
-                        }
-                    }
-                    helper.flushAcks();
-                    self.setZooKeeperServer(zk);
-                    self.adminServer.setZooKeeperServer(zk);
-                    break outerLoop;
-                case Leader.NEWLEADER: // Getting NEWLEADER here instead of in discovery
-                    LOG.info("Learner received NEWLEADER message");
-                    if (qp.getData() != null && qp.getData().length > 1) {
-                        try {
-                            QuorumVerifier qv = self.configFromString(new String(qp.getData(), UTF_8));
-                            self.setLastSeenQuorumVerifier(qv, true);
-                            newLeaderQV = qv;
-                        } catch (Exception e) {
-                            e.printStackTrace();
-                        }
-                    }
-
-                    helper.writeState();
-                    writePacket(new QuorumPacket(Leader.ACK, newLeaderZxid, null, null), true);
-                    break;
-                }
-            }
-        }
-        QuorumPacket ack = new QuorumPacket(Leader.ACK, 0, null, null);
-        ack.setZxid(ZxidUtils.makeZxid(newEpoch, 0));
-        writePacket(ack, true);
-        zk.startServing();
-        /*
-         * Update the election vote here to ensure that all members of the
-         * ensemble report the same vote to new servers that start up and
-         * send leader election notifications to the ensemble.
-         *
-         * @see https://issues.apache.org/jira/browse/ZOOKEEPER-1732
-         */
-        self.updateElectionVote(newEpoch);
-
-        helper.applyDelayedPackets();
-    }
-
-    private void tryReconfig(PacketInFlight pif, long newLeader, long zxid) throws Exception {
-        QuorumVerifier qv = self.configFromString(new String(((SetDataTxn) pif.rec).getData(), UTF_8));
-        boolean majorChange = self.processReconfig(qv, newLeader, zxid, true);
-        if (majorChange) {
-            throw new Exception("changes proposed in reconfig");
-        }
-    }
-
-    protected void revalidate(QuorumPacket qp) throws IOException {
-        ByteArrayInputStream bis = new ByteArrayInputStream(qp.getData());
-        DataInputStream dis = new DataInputStream(bis);
-        long sessionId = dis.readLong();
-        boolean valid = dis.readBoolean();
-        ServerCnxn cnxn = pendingRevalidations.remove(sessionId);
-        if (cnxn == null) {
-            LOG.warn("Missing session 0x{} for validation", Long.toHexString(sessionId));
-        } else {
-            zk.finishSessionInit(cnxn, valid);
-        }
-        if (LOG.isTraceEnabled()) {
-            ZooTrace.logTraceMessage(
-                LOG,
-                ZooTrace.SESSION_TRACE_MASK,
-                "Session 0x" + Long.toHexString(sessionId) + " is valid: " + valid);
-        }
-    }
-
-    protected void ping(QuorumPacket qp) throws IOException {
-        // Send back the ping with our session data
-        ByteArrayOutputStream bos = new ByteArrayOutputStream();
-        DataOutputStream dos = new DataOutputStream(bos);
-        Map<Long, Integer> touchTable = zk.getTouchSnapshot();
-        for (Entry<Long, Integer> entry : touchTable.entrySet()) {
-            dos.writeLong(entry.getKey());
-            dos.writeInt(entry.getValue());
-        }
-
-        QuorumPacket pingReply = new QuorumPacket(qp.getType(), qp.getZxid(), bos.toByteArray(), qp.getAuthinfo());
-        writePacket(pingReply, true);
-    }
-
-    /**
-     * Shutdown the Peer
-     */
-    public void shutdown() {
-        self.setZooKeeperServer(null);
-        self.closeAllConnections();
-        self.adminServer.setZooKeeperServer(null);
-
-        if (sender != null) {
-            sender.shutdown();
-        }
-
-        closeSocket();
-        // shutdown previous zookeeper
-        if (zk != null) {
-            // If we haven't finished SNAP sync, force fully shutdown
-            // to avoid potential inconsistency
-            zk.shutdown(self.getSyncMode().equals(QuorumPeer.SyncMode.SNAP));
-        }
-    }
-
-    boolean isRunning() {
-        return self.isRunning() && zk.isRunning();
-    }
-
-    void closeSocket() {
-        if (sock != null) {
-            if (sockBeingClosed.compareAndSet(false, true)) {
-                if (closeSocketAsync) {
-                    final Thread closingThread = new Thread(() -> closeSockSync(), "CloseSocketThread(sid:" + zk.getServerId());
-                    closingThread.setDaemon(true);
-                    closingThread.start();
-                } else {
-                    closeSockSync();
-                }
-            }
-        }
-    }
-
-    void closeSockSync() {
-        try {
-            long startTime = Time.currentElapsedTime();
-            if (sock != null) {
-                sock.close();
-                sock = null;
-            }
-            ServerMetrics.getMetrics().SOCKET_CLOSING_TIME.add(Time.currentElapsedTime() - startTime);
-        } catch (IOException e) {
-            LOG.warn("Ignoring error closing connection to leader", e);
-        }
-    }
-
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/LearnerZooKeeperServer.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/LearnerZooKeeperServer.java
deleted file mode 100644
index 99c4ae16dce..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/LearnerZooKeeperServer.java
+++ /dev/null
@@ -1,180 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.zookeeper.server.quorum;
-
-import java.io.IOException;
-import java.util.Map;
-import org.apache.zookeeper.jmx.MBeanRegistry;
-import org.apache.zookeeper.server.DataTreeBean;
-import org.apache.zookeeper.server.ServerCnxn;
-import org.apache.zookeeper.server.SyncRequestProcessor;
-import org.apache.zookeeper.server.ZKDatabase;
-import org.apache.zookeeper.server.ZooKeeperServerBean;
-import org.apache.zookeeper.server.persistence.FileTxnSnapLog;
-
-/**
- * Parent class for all ZooKeeperServers for Learners
- */
-public abstract class LearnerZooKeeperServer extends QuorumZooKeeperServer {
-
-    /*
-     * Request processors
-     */
-    protected CommitProcessor commitProcessor;
-    protected SyncRequestProcessor syncProcessor;
-
-    public LearnerZooKeeperServer(FileTxnSnapLog logFactory, int tickTime, int minSessionTimeout, int maxSessionTimeout, int listenBacklog, ZKDatabase zkDb, QuorumPeer self) throws IOException {
-        super(logFactory, tickTime, minSessionTimeout, maxSessionTimeout, listenBacklog, zkDb, self);
-    }
-
-    /**
-     * Abstract method to return the learner associated with this server.
-     * Since the Learner may change under our feet (when QuorumPeer reassigns
-     * it) we can't simply take a reference here. Instead, we need the
-     * subclasses to implement this.
-     */
-    public abstract Learner getLearner();
-
-    /**
-     * Returns the current state of the session tracker. This is only currently
-     * used by a Learner to build a ping response packet.
-     *
-     */
-    protected Map<Long, Integer> getTouchSnapshot() {
-        if (sessionTracker != null) {
-            return ((LearnerSessionTracker) sessionTracker).snapshot();
-        }
-        Map<Long, Integer> map = Map.of();
-        return map;
-    }
-
-    /**
-     * Returns the id of the associated QuorumPeer, which will do for a unique
-     * id of this server.
-     */
-    @Override
-    public long getServerId() {
-        return self.getMyId();
-    }
-
-    @Override
-    public void createSessionTracker() {
-        sessionTracker = new LearnerSessionTracker(
-            this,
-            getZKDatabase().getSessionWithTimeOuts(),
-            this.tickTime,
-            self.getMyId(),
-            self.areLocalSessionsEnabled(),
-            getZooKeeperServerListener());
-    }
-
-    @Override
-    protected void revalidateSession(ServerCnxn cnxn, long sessionId, int sessionTimeout) throws IOException {
-        if (upgradeableSessionTracker.isLocalSession(sessionId)) {
-            super.revalidateSession(cnxn, sessionId, sessionTimeout);
-        } else {
-            getLearner().validateSession(cnxn, sessionId, sessionTimeout);
-        }
-    }
-
-    @Override
-    protected void registerJMX() {
-        // register with JMX
-        try {
-            jmxDataTreeBean = new DataTreeBean(getZKDatabase().getDataTree());
-            MBeanRegistry.getInstance().register(jmxDataTreeBean, jmxServerBean);
-        } catch (Exception e) {
-            LOG.warn("Failed to register with JMX", e);
-            jmxDataTreeBean = null;
-        }
-    }
-
-    public void registerJMX(ZooKeeperServerBean serverBean, LocalPeerBean localPeerBean) {
-        // register with JMX
-        if (self.jmxLeaderElectionBean != null) {
-            try {
-                MBeanRegistry.getInstance().unregister(self.jmxLeaderElectionBean);
-            } catch (Exception e) {
-                LOG.warn("Failed to register with JMX", e);
-            }
-            self.jmxLeaderElectionBean = null;
-        }
-
-        try {
-            jmxServerBean = serverBean;
-            MBeanRegistry.getInstance().register(serverBean, localPeerBean);
-        } catch (Exception e) {
-            LOG.warn("Failed to register with JMX", e);
-            jmxServerBean = null;
-        }
-    }
-
-    @Override
-    protected void unregisterJMX() {
-        // unregister from JMX
-        try {
-            if (jmxDataTreeBean != null) {
-                MBeanRegistry.getInstance().unregister(jmxDataTreeBean);
-            }
-        } catch (Exception e) {
-            LOG.warn("Failed to unregister with JMX", e);
-        }
-        jmxDataTreeBean = null;
-    }
-
-    protected void unregisterJMX(Learner peer) {
-        // unregister from JMX
-        try {
-            if (jmxServerBean != null) {
-                MBeanRegistry.getInstance().unregister(jmxServerBean);
-            }
-        } catch (Exception e) {
-            LOG.warn("Failed to unregister with JMX", e);
-        }
-        jmxServerBean = null;
-    }
-
-    @Override
-    public synchronized void shutdown(boolean fullyShutDown) {
-        if (!canShutdown()) {
-            LOG.debug("ZooKeeper server is not running, so not proceeding to shutdown!");
-        } else {
-            LOG.info("Shutting down");
-            try {
-                if (syncProcessor != null) {
-                    // Shutting down the syncProcessor here, first, ensures queued transactions here are written to
-                    // permanent storage, which ensures that crash recovery data is consistent with what is used for a
-                    // leader election immediately following shutdown, because of the old leader going down; and also
-                    // that any state on its way to being written is also loaded in the potential call to
-                    // fast-forward-from-edits, in super.shutdown(...), so we avoid getting a DIFF from the new leader
-                    // that contains entries we have already written to our transaction log.
-                    syncProcessor.shutdown();
-                }
-            } catch (Exception e) {
-                LOG.warn("Ignoring unexpected exception in syncprocessor shutdown", e);
-            }
-        }
-        try {
-            super.shutdown(fullyShutDown);
-        } catch (Exception e) {
-            LOG.warn("Ignoring unexpected exception during shutdown", e);
-        }
-    }
-
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/ObserverZooKeeperServer.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/ObserverZooKeeperServer.java
deleted file mode 100644
index 1a44a98e6e7..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/ObserverZooKeeperServer.java
+++ /dev/null
@@ -1,136 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.zookeeper.server.quorum;
-
-import java.io.IOException;
-import java.util.concurrent.ConcurrentLinkedQueue;
-import java.util.function.BiConsumer;
-import org.apache.zookeeper.server.FinalRequestProcessor;
-import org.apache.zookeeper.server.Request;
-import org.apache.zookeeper.server.RequestProcessor;
-import org.apache.zookeeper.server.SyncRequestProcessor;
-import org.apache.zookeeper.server.ZKDatabase;
-import org.apache.zookeeper.server.persistence.FileTxnSnapLog;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-/**
- * A ZooKeeperServer for the Observer node type. Not much is different, but
- * we anticipate specializing the request processors in the future.
- *
- */
-public class ObserverZooKeeperServer extends LearnerZooKeeperServer {
-
-    private static final Logger LOG = LoggerFactory.getLogger(ObserverZooKeeperServer.class);
-
-    /**
-     * Enable since request processor for writing txnlog to disk and
-     * take periodic snapshot. Default is ON.
-     */
-
-    private boolean syncRequestProcessorEnabled = this.self.getSyncEnabled();
-
-    /*
-     * Pending sync requests
-     */ ConcurrentLinkedQueue<Request> pendingSyncs = new ConcurrentLinkedQueue<>();
-
-    ObserverZooKeeperServer(FileTxnSnapLog logFactory, QuorumPeer self, ZKDatabase zkDb) throws IOException {
-        super(logFactory, self.tickTime, self.minSessionTimeout, self.maxSessionTimeout, self.clientPortListenBacklog, zkDb, self);
-        LOG.info("syncEnabled ={}", syncRequestProcessorEnabled);
-    }
-
-    public Observer getObserver() {
-        return self.observer;
-    }
-
-    @Override
-    public Learner getLearner() {
-        return self.observer;
-    }
-
-    /**
-     * Unlike a Follower, which sees a full request only during the PROPOSAL
-     * phase, Observers get all the data required with the INFORM packet.
-     * This method commits a request that has been unpacked by from an INFORM
-     * received from the Leader.
-     *
-     * @param request
-     */
-    public void commitRequest(Request request) {
-        if (syncProcessor != null) {
-            // Write to txnlog and take periodic snapshot
-            syncProcessor.processRequest(request);
-        }
-        commitProcessor.commit(request);
-    }
-
-    /**
-     * Set up the request processors for an Observer:
-     * firstProcesor-&gt;commitProcessor-&gt;finalProcessor
-     */
-    @Override
-    protected void setupRequestProcessors() {
-        // We might consider changing the processor behaviour of
-        // Observers to, for example, remove the disk sync requirements.
-        // Currently, they behave almost exactly the same as followers.
-        RequestProcessor finalProcessor = new FinalRequestProcessor(this);
-        commitProcessor = new CommitProcessor(finalProcessor, Long.toString(getServerId()), true, getZooKeeperServerListener());
-        commitProcessor.start();
-        firstProcessor = new ObserverRequestProcessor(this, commitProcessor);
-        ((ObserverRequestProcessor) firstProcessor).start();
-
-        /*
-         * Observer should write to disk, so that the it won't request
-         * too old txn from the leader which may lead to getting an entire
-         * snapshot.
-         *
-         * However, this may degrade performance as it has to write to disk
-         * and do periodic snapshot which may double the memory requirements
-         */
-        if (syncRequestProcessorEnabled) {
-            syncProcessor = new SyncRequestProcessor(this, null);
-            syncProcessor.start();
-        }
-    }
-
-    /*
-     * Process a sync request
-     */
-    public synchronized void sync() {
-        if (pendingSyncs.size() == 0) {
-            LOG.warn("Not expecting a sync.");
-            return;
-        }
-
-        Request r = pendingSyncs.remove();
-        commitProcessor.commit(r);
-    }
-
-    @Override
-    public String getState() {
-        return "observer";
-    }
-
-    @Override
-    public void dumpMonitorValues(BiConsumer<String, Object> response) {
-        super.dumpMonitorValues(response);
-        response.accept("observer_master_id", getObserver().getLearnerMasterId());
-    }
-
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/QuorumPeer.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/QuorumPeer.java
deleted file mode 100644
index f6fc87d7716..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/QuorumPeer.java
+++ /dev/null
@@ -1,2711 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.zookeeper.server.quorum;
-
-import static org.apache.zookeeper.common.NetUtils.formatInetAddr;
-import java.io.BufferedReader;
-import java.io.File;
-import java.io.FileNotFoundException;
-import java.io.FileReader;
-import java.io.IOException;
-import java.io.StringReader;
-import java.io.StringWriter;
-import java.io.Writer;
-import java.net.DatagramPacket;
-import java.net.DatagramSocket;
-import java.net.InetAddress;
-import java.net.InetSocketAddress;
-import java.nio.ByteBuffer;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.Comparator;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Map;
-import java.util.Map.Entry;
-import java.util.Properties;
-import java.util.Set;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicInteger;
-import java.util.concurrent.atomic.AtomicLong;
-import java.util.concurrent.atomic.AtomicReference;
-import java.util.function.Function;
-import java.util.stream.Collectors;
-import java.util.stream.IntStream;
-import javax.security.sasl.SaslException;
-import org.apache.yetus.audience.InterfaceAudience;
-import org.apache.zookeeper.KeeperException.BadArgumentsException;
-import org.apache.zookeeper.common.AtomicFileOutputStream;
-import org.apache.zookeeper.common.AtomicFileWritingIdiom;
-import org.apache.zookeeper.common.AtomicFileWritingIdiom.WriterStatement;
-import org.apache.zookeeper.common.QuorumX509Util;
-import org.apache.zookeeper.common.Time;
-import org.apache.zookeeper.common.X509Exception;
-import org.apache.zookeeper.jmx.MBeanRegistry;
-import org.apache.zookeeper.jmx.ZKMBeanInfo;
-import org.apache.zookeeper.server.ServerCnxn;
-import org.apache.zookeeper.server.ServerCnxnFactory;
-import org.apache.zookeeper.server.ServerMetrics;
-import org.apache.zookeeper.server.ZKDatabase;
-import org.apache.zookeeper.server.ZooKeeperServer;
-import org.apache.zookeeper.server.ZooKeeperThread;
-import org.apache.zookeeper.server.admin.AdminServer;
-import org.apache.zookeeper.server.admin.AdminServer.AdminServerException;
-import org.apache.zookeeper.server.admin.AdminServerFactory;
-import org.apache.zookeeper.server.persistence.FileTxnSnapLog;
-import org.apache.zookeeper.server.quorum.QuorumPeerConfig.ConfigException;
-import org.apache.zookeeper.server.quorum.auth.NullQuorumAuthLearner;
-import org.apache.zookeeper.server.quorum.auth.NullQuorumAuthServer;
-import org.apache.zookeeper.server.quorum.auth.QuorumAuth;
-import org.apache.zookeeper.server.quorum.auth.QuorumAuthLearner;
-import org.apache.zookeeper.server.quorum.auth.QuorumAuthServer;
-import org.apache.zookeeper.server.quorum.auth.SaslQuorumAuthLearner;
-import org.apache.zookeeper.server.quorum.auth.SaslQuorumAuthServer;
-import org.apache.zookeeper.server.quorum.flexible.QuorumMaj;
-import org.apache.zookeeper.server.quorum.flexible.QuorumOracleMaj;
-import org.apache.zookeeper.server.quorum.flexible.QuorumVerifier;
-import org.apache.zookeeper.server.util.ConfigUtils;
-import org.apache.zookeeper.server.util.JvmPauseMonitor;
-import org.apache.zookeeper.server.util.ZxidUtils;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-/**
- * This class manages the quorum protocol. There are three states this server
- * can be in:
- * <ol>
- * <li>Leader election - each server will elect a leader (proposing itself as a
- * leader initially).</li>
- * <li>Follower - the server will synchronize with the leader and replicate any
- * transactions.</li>
- * <li>Leader - the server will process requests and forward them to followers.
- * A majority of followers must log the request before it can be accepted.
- * </ol>
- *
- * This class will setup a datagram socket that will always respond with its
- * view of the current leader. The response will take the form of:
- *
- * <pre>
- * int xid;
- *
- * long myid;
- *
- * long leader_id;
- *
- * long leader_zxid;
- * </pre>
- *
- * The request for the current leader will consist solely of an xid: int xid;
- */
-public class QuorumPeer extends ZooKeeperThread implements QuorumStats.Provider {
-
-    private static final Logger LOG = LoggerFactory.getLogger(QuorumPeer.class);
-
-    public static final String CONFIG_KEY_KERBEROS_CANONICALIZE_HOST_NAMES = "zookeeper.kerberos.canonicalizeHostNames";
-    public static final String CONFIG_DEFAULT_KERBEROS_CANONICALIZE_HOST_NAMES = "false";
-
-    private QuorumBean jmxQuorumBean;
-    LocalPeerBean jmxLocalPeerBean;
-    private Map<Long, RemotePeerBean> jmxRemotePeerBean;
-    LeaderElectionBean jmxLeaderElectionBean;
-
-    // The QuorumCnxManager is held through an AtomicReference to ensure cross-thread visibility
-    // of updates; see the implementation comment at setLastSeenQuorumVerifier().
-    private AtomicReference<QuorumCnxManager> qcmRef = new AtomicReference<>();
-
-    QuorumAuthServer authServer;
-    QuorumAuthLearner authLearner;
-
-    /**
-     * ZKDatabase is a top level member of quorumpeer
-     * which will be used in all the zookeeperservers
-     * instantiated later. Also, it is created once on
-     * bootup and only thrown away in case of a truncate
-     * message from the leader
-     */
-    private ZKDatabase zkDb;
-
-    private JvmPauseMonitor jvmPauseMonitor;
-
-    private final AtomicBoolean suspended = new AtomicBoolean(false);
-
-    public static final class AddressTuple {
-
-        public final MultipleAddresses quorumAddr;
-        public final MultipleAddresses electionAddr;
-        public final InetSocketAddress clientAddr;
-
-        public AddressTuple(MultipleAddresses quorumAddr, MultipleAddresses electionAddr, InetSocketAddress clientAddr) {
-            this.quorumAddr = quorumAddr;
-            this.electionAddr = electionAddr;
-            this.clientAddr = clientAddr;
-        }
-
-    }
-
-    private int observerMasterPort;
-
-    public int getObserverMasterPort() {
-        return observerMasterPort;
-    }
-
-    public void setObserverMasterPort(int observerMasterPort) {
-        this.observerMasterPort = observerMasterPort;
-    }
-
-    public static final String CONFIG_KEY_MULTI_ADDRESS_ENABLED = "zookeeper.multiAddress.enabled";
-    public static final String CONFIG_DEFAULT_MULTI_ADDRESS_ENABLED = "false";
-
-    private boolean multiAddressEnabled = true;
-    public boolean isMultiAddressEnabled() {
-        return multiAddressEnabled;
-    }
-
-    public void setMultiAddressEnabled(boolean multiAddressEnabled) {
-        this.multiAddressEnabled = multiAddressEnabled;
-        LOG.info("multiAddress.enabled set to {}", multiAddressEnabled);
-    }
-
-    public static final String CONFIG_KEY_MULTI_ADDRESS_REACHABILITY_CHECK_TIMEOUT_MS = "zookeeper.multiAddress.reachabilityCheckTimeoutMs";
-
-    private int multiAddressReachabilityCheckTimeoutMs = (int) MultipleAddresses.DEFAULT_TIMEOUT.toMillis();
-    public int getMultiAddressReachabilityCheckTimeoutMs() {
-        return multiAddressReachabilityCheckTimeoutMs;
-    }
-
-    public void setMultiAddressReachabilityCheckTimeoutMs(int multiAddressReachabilityCheckTimeoutMs) {
-        this.multiAddressReachabilityCheckTimeoutMs = multiAddressReachabilityCheckTimeoutMs;
-        LOG.info("multiAddress.reachabilityCheckTimeoutMs set to {}", multiAddressReachabilityCheckTimeoutMs);
-    }
-
-    public static final String CONFIG_KEY_MULTI_ADDRESS_REACHABILITY_CHECK_ENABLED = "zookeeper.multiAddress.reachabilityCheckEnabled";
-
-    private boolean multiAddressReachabilityCheckEnabled = true;
-
-    public boolean isMultiAddressReachabilityCheckEnabled() {
-        return multiAddressReachabilityCheckEnabled;
-    }
-
-    public void setMultiAddressReachabilityCheckEnabled(boolean multiAddressReachabilityCheckEnabled) {
-        this.multiAddressReachabilityCheckEnabled = multiAddressReachabilityCheckEnabled;
-        LOG.info("multiAddress.reachabilityCheckEnabled set to {}", multiAddressReachabilityCheckEnabled);
-    }
-
-    public static class QuorumServer {
-
-        public MultipleAddresses addr = new MultipleAddresses();
-
-        public MultipleAddresses electionAddr = new MultipleAddresses();
-
-        public InetSocketAddress clientAddr = null;
-
-        public long id;
-
-        public String hostname;
-
-        public LearnerType type = LearnerType.PARTICIPANT;
-
-        public boolean isClientAddrFromStatic = false;
-
-        private List<InetSocketAddress> myAddrs;
-
-        public QuorumServer(long id, InetSocketAddress addr, InetSocketAddress electionAddr, InetSocketAddress clientAddr) {
-            this(id, addr, electionAddr, clientAddr, LearnerType.PARTICIPANT);
-        }
-
-        public QuorumServer(long id, InetSocketAddress addr, InetSocketAddress electionAddr) {
-            this(id, addr, electionAddr, null, LearnerType.PARTICIPANT);
-        }
-
-        // VisibleForTesting
-        public QuorumServer(long id, InetSocketAddress addr) {
-            this(id, addr, null, null, LearnerType.PARTICIPANT);
-        }
-
-        public long getId() {
-            return id;
-        }
-
-        /**
-         * Performs a DNS lookup for server address and election address.
-         *
-         * If the DNS lookup fails, this.addr and electionAddr remain
-         * unmodified.
-         */
-        public void recreateSocketAddresses() {
-            if (this.addr.isEmpty()) {
-                LOG.warn("Server address has not been initialized");
-                return;
-            }
-            if (this.electionAddr.isEmpty()) {
-                LOG.warn("Election address has not been initialized");
-                return;
-            }
-            this.addr.recreateSocketAddresses();
-            this.electionAddr.recreateSocketAddresses();
-        }
-
-        private LearnerType getType(String s) throws ConfigException {
-            switch (s.trim().toLowerCase()) {
-                case "observer":
-                    return LearnerType.OBSERVER;
-                case "participant":
-                    return LearnerType.PARTICIPANT;
-                default:
-                    throw new ConfigException("Unrecognised peertype: " + s);
-            }
-        }
-
-        public QuorumServer(long sid, String addressStr) throws ConfigException {
-            this(sid, addressStr, QuorumServer::getInetAddress);
-        }
-
-        QuorumServer(long sid, String addressStr, Function<InetSocketAddress, InetAddress> getInetAddress) throws ConfigException {
-            this.id = sid;
-            initializeWithAddressString(addressStr, getInetAddress);
-        }
-
-        public QuorumServer(long id, InetSocketAddress addr, InetSocketAddress electionAddr, LearnerType type) {
-            this(id, addr, electionAddr, null, type);
-        }
-
-        public QuorumServer(long id, InetSocketAddress addr, InetSocketAddress electionAddr, InetSocketAddress clientAddr, LearnerType type) {
-            this.id = id;
-            if (addr != null) {
-                this.addr.addAddress(addr);
-            }
-            if (electionAddr != null) {
-                this.electionAddr.addAddress(electionAddr);
-            }
-            this.type = type;
-            this.clientAddr = clientAddr;
-
-            setMyAddrs();
-        }
-
-        private static final String wrongFormat =
-            " does not have the form server_config or server_config;client_config"
-            + " where server_config is the pipe separated list of host:port:port or host:port:port:type"
-            + " and client_config is port or host:port";
-
-        private void initializeWithAddressString(String addressStr, Function<InetSocketAddress, InetAddress> getInetAddress) throws ConfigException {
-            LearnerType newType = null;
-            String[] serverClientParts = addressStr.split(";");
-            String[] serverAddresses = serverClientParts[0].split("\\|");
-
-            if (serverClientParts.length == 2) {
-                String[] clientParts = ConfigUtils.getHostAndPort(serverClientParts[1]);
-                if (clientParts.length > 2) {
-                    throw new ConfigException(addressStr + wrongFormat);
-                }
-
-                // is client_config a host:port or just a port
-                String clientHostName = (clientParts.length == 2) ? clientParts[0] : "0.0.0.0";
-                try {
-                    clientAddr = new InetSocketAddress(clientHostName, Integer.parseInt(clientParts[clientParts.length - 1]));
-                } catch (NumberFormatException e) {
-                    throw new ConfigException("Address unresolved: " + hostname + ":" + clientParts[clientParts.length - 1]);
-                }
-            }
-
-            boolean multiAddressEnabled = Boolean.parseBoolean(
-                System.getProperty(QuorumPeer.CONFIG_KEY_MULTI_ADDRESS_ENABLED, QuorumPeer.CONFIG_DEFAULT_MULTI_ADDRESS_ENABLED));
-            if (!multiAddressEnabled && serverAddresses.length > 1) {
-                throw new ConfigException("Multiple address feature is disabled, but multiple addresses were specified for sid " + this.id);
-            }
-
-            boolean canonicalize = Boolean.parseBoolean(
-                System.getProperty(
-                    CONFIG_KEY_KERBEROS_CANONICALIZE_HOST_NAMES,
-                    CONFIG_DEFAULT_KERBEROS_CANONICALIZE_HOST_NAMES));
-
-            for (String serverAddress : serverAddresses) {
-                String serverParts[] = ConfigUtils.getHostAndPort(serverAddress);
-                if ((serverClientParts.length > 2) || (serverParts.length < 3)
-                        || (serverParts.length > 4)) {
-                    throw new ConfigException(addressStr + wrongFormat);
-                }
-
-                String serverHostName = serverParts[0];
-
-                // server_config should be either host:port:port or host:port:port:type
-                InetSocketAddress tempAddress;
-                InetSocketAddress tempElectionAddress;
-                try {
-                    tempAddress = new InetSocketAddress(serverHostName, Integer.parseInt(serverParts[1]));
-                    addr.addAddress(tempAddress);
-                } catch (NumberFormatException e) {
-                    throw new ConfigException("Address unresolved: " + serverHostName + ":" + serverParts[1]);
-                }
-                try {
-                    tempElectionAddress = new InetSocketAddress(serverHostName, Integer.parseInt(serverParts[2]));
-                    electionAddr.addAddress(tempElectionAddress);
-                } catch (NumberFormatException e) {
-                    throw new ConfigException("Address unresolved: " + serverHostName + ":" + serverParts[2]);
-                }
-
-                if (tempAddress.getPort() == tempElectionAddress.getPort()) {
-                    throw new ConfigException("Client and election port must be different! Please update the "
-                            + "configuration file on server." + this.id);
-                }
-
-                if (canonicalize) {
-                    InetAddress ia = getInetAddress.apply(tempAddress);
-                    if (ia == null) {
-                        throw new ConfigException("Unable to canonicalize address " + serverHostName + " because it's not resolvable");
-                    }
-
-                    String canonicalHostName = ia.getCanonicalHostName();
-
-                    if (!canonicalHostName.equals(serverHostName)
-                        // Avoid using literal IP address when
-                        // security check fails
-                        && !canonicalHostName.equals(ia.getHostAddress())) {
-                        LOG.info("Host name for quorum server {} "
-                            + "canonicalized from {} to {}",
-                            this.id, serverHostName, canonicalHostName);
-                        serverHostName = canonicalHostName;
-                    }
-                }
-
-                if (serverParts.length == 4) {
-                    LearnerType tempType = getType(serverParts[3]);
-                    if (newType == null) {
-                        newType = tempType;
-                    }
-
-                    if (newType != tempType) {
-                        throw new ConfigException("Multiple addresses should have similar roles: " + type + " vs " + tempType);
-                    }
-                }
-
-                this.hostname = serverHostName;
-            }
-
-            if (newType != null) {
-                type = newType;
-            }
-
-            setMyAddrs();
-        }
-
-        private static InetAddress getInetAddress(InetSocketAddress addr) {
-            return addr.getAddress();
-        }
-
-        private void setMyAddrs() {
-            this.myAddrs = new ArrayList<>();
-            this.myAddrs.addAll(this.addr.getAllAddresses());
-            this.myAddrs.add(this.clientAddr);
-            this.myAddrs.addAll(this.electionAddr.getAllAddresses());
-            this.myAddrs = excludedSpecialAddresses(this.myAddrs);
-        }
-
-        public static String delimitedHostString(InetSocketAddress addr) {
-            String host = addr.getHostString();
-            if (host.contains(":")) {
-                return "[" + host + "]";
-            } else {
-                return host;
-            }
-        }
-
-        public String toString() {
-            StringWriter sw = new StringWriter();
-
-            List<InetSocketAddress> addrList = new LinkedList<>(addr.getAllAddresses());
-            List<InetSocketAddress> electionAddrList = new LinkedList<>(electionAddr.getAllAddresses());
-
-            if (addrList.size() > 0 && electionAddrList.size() > 0) {
-                addrList.sort(Comparator.comparing(InetSocketAddress::getHostString));
-                electionAddrList.sort(Comparator.comparing(InetSocketAddress::getHostString));
-                sw.append(IntStream.range(0, addrList.size()).mapToObj(i -> String.format("%s:%d:%d",
-                        delimitedHostString(addrList.get(i)), addrList.get(i).getPort(), electionAddrList.get(i).getPort()))
-                        .collect(Collectors.joining("|")));
-            }
-
-            if (type == LearnerType.OBSERVER) {
-                sw.append(":observer");
-            } else if (type == LearnerType.PARTICIPANT) {
-                sw.append(":participant");
-            }
-
-            if (clientAddr != null && !isClientAddrFromStatic) {
-                sw.append(";");
-                sw.append(delimitedHostString(clientAddr));
-                sw.append(":");
-                sw.append(String.valueOf(clientAddr.getPort()));
-            }
-
-            return sw.toString();
-        }
-
-        public int hashCode() {
-            assert false : "hashCode not designed";
-            return 42; // any arbitrary constant will do
-        }
-
-        private boolean checkAddressesEqual(InetSocketAddress addr1, InetSocketAddress addr2) {
-            return (addr1 != null || addr2 == null)
-                   && (addr1 == null || addr2 != null)
-                   && (addr1 == null || addr2 == null || addr1.equals(addr2));
-        }
-
-        public boolean equals(Object o) {
-            if (!(o instanceof QuorumServer)) {
-                return false;
-            }
-            QuorumServer qs = (QuorumServer) o;
-            if ((qs.id != id) || (qs.type != type)) {
-                return false;
-            }
-            if (!addr.equals(qs.addr)) {
-                return false;
-            }
-            if (!electionAddr.equals(qs.electionAddr)) {
-                return false;
-            }
-            return checkAddressesEqual(clientAddr, qs.clientAddr);
-        }
-
-        public void checkAddressDuplicate(QuorumServer s) throws BadArgumentsException {
-            List<InetSocketAddress> otherAddrs = new ArrayList<>(s.addr.getAllAddresses());
-            otherAddrs.add(s.clientAddr);
-            otherAddrs.addAll(s.electionAddr.getAllAddresses());
-            otherAddrs = excludedSpecialAddresses(otherAddrs);
-
-            for (InetSocketAddress my : this.myAddrs) {
-
-                for (InetSocketAddress other : otherAddrs) {
-                    if (my.equals(other)) {
-                        String error = String.format("%s of server.%d conflicts %s of server.%d", my, this.id, other, s.id);
-                        throw new BadArgumentsException(error);
-                    }
-                }
-            }
-        }
-
-        private List<InetSocketAddress> excludedSpecialAddresses(List<InetSocketAddress> addrs) {
-            List<InetSocketAddress> included = new ArrayList<>();
-
-            for (InetSocketAddress addr : addrs) {
-                if (addr == null) {
-                    continue;
-                }
-                InetAddress inetaddr = addr.getAddress();
-
-                if (inetaddr == null || inetaddr.isAnyLocalAddress() // wildCard addresses (0.0.0.0 or [::])
-                    || inetaddr.isLoopbackAddress()) { // loopback address(localhost/127.0.0.1)
-                    continue;
-                }
-                included.add(addr);
-            }
-            return included;
-        }
-
-    }
-
-    public enum ServerState {
-        LOOKING,
-        FOLLOWING,
-        LEADING,
-        OBSERVING
-    }
-
-    /**
-     * (Used for monitoring) shows the current phase of
-     * Zab protocol that peer is running.
-     */
-    public enum ZabState {
-        ELECTION,
-        DISCOVERY,
-        SYNCHRONIZATION,
-        BROADCAST
-    }
-
-    /**
-     * (Used for monitoring) When peer is in synchronization phase, this shows
-     * which synchronization mechanism is being used
-     */
-    public enum SyncMode {
-        NONE,
-        DIFF,
-        SNAP,
-        TRUNC
-    }
-
-    /*
-     * A peer can either be participating, which implies that it is willing to
-     * both vote in instances of consensus and to elect or become a Leader, or
-     * it may be observing in which case it isn't.
-     *
-     * We need this distinction to decide which ServerState to move to when
-     * conditions change (e.g. which state to become after LOOKING).
-     */
-    public enum LearnerType {
-        PARTICIPANT,
-        OBSERVER
-    }
-
-    /*
-     * To enable observers to have no identifier, we need a generic identifier
-     * at least for QuorumCnxManager. We use the following constant to as the
-     * value of such a generic identifier.
-     */
-
-    static final long OBSERVER_ID = Long.MAX_VALUE;
-
-    /*
-     * Record leader election time
-     */
-    public long start_fle, end_fle; // fle = fast leader election
-    public static final String FLE_TIME_UNIT = "MS";
-    private long unavailableStartTime;
-
-    /*
-     * Default value of peer is participant
-     */
-    private LearnerType learnerType = LearnerType.PARTICIPANT;
-
-    public LearnerType getLearnerType() {
-        return learnerType;
-    }
-
-    /**
-     * Sets the LearnerType
-     */
-    public void setLearnerType(LearnerType p) {
-        learnerType = p;
-    }
-
-    protected synchronized void setConfigFileName(String s) {
-        configFilename = s;
-    }
-
-    private String configFilename = null;
-
-    public int getQuorumSize() {
-        return getVotingView().size();
-    }
-
-    public void setJvmPauseMonitor(JvmPauseMonitor jvmPauseMonitor) {
-        this.jvmPauseMonitor = jvmPauseMonitor;
-    }
-
-    /**
-     * QuorumVerifier implementation; default (majority).
-     */
-
-    //last committed quorum verifier
-    private QuorumVerifier quorumVerifier;
-
-    //last proposed quorum verifier
-    private QuorumVerifier lastSeenQuorumVerifier = null;
-
-    // Lock object that guard access to quorumVerifier and lastSeenQuorumVerifier.
-    final Object QV_LOCK = new Object();
-
-    /**
-     * My id
-     */
-    private long myid;
-
-    /**
-     * get the id of this quorum peer.
-     */
-    public long getMyId() {
-        return myid;
-    }
-
-    // VisibleForTesting
-    void setId(long id) {
-        this.myid = id;
-    }
-
-    private boolean sslQuorum;
-    private boolean shouldUsePortUnification;
-
-    public boolean isSslQuorum() {
-        return sslQuorum;
-    }
-
-    public boolean shouldUsePortUnification() {
-        return shouldUsePortUnification;
-    }
-
-    private final QuorumX509Util x509Util;
-
-    QuorumX509Util getX509Util() {
-        return x509Util;
-    }
-
-    /**
-     * This is who I think the leader currently is.
-     */
-    private volatile Vote currentVote;
-
-    public synchronized Vote getCurrentVote() {
-        return currentVote;
-    }
-
-    public synchronized void setCurrentVote(Vote v) {
-        currentVote = v;
-    }
-
-    private volatile boolean running = true;
-
-    private String initialConfig;
-
-    /**
-     * The number of milliseconds of each tick
-     */
-    protected int tickTime;
-
-    /**
-     * Whether learners in this quorum should create new sessions as local.
-     * False by default to preserve existing behavior.
-     */
-    protected boolean localSessionsEnabled = false;
-
-    /**
-     * Whether learners in this quorum should upgrade local sessions to
-     * global. Only matters if local sessions are enabled.
-     */
-    protected boolean localSessionsUpgradingEnabled = true;
-
-    /**
-     * Minimum number of milliseconds to allow for session timeout.
-     * A value of -1 indicates unset, use default.
-     */
-    protected int minSessionTimeout = -1;
-
-    /**
-     * Maximum number of milliseconds to allow for session timeout.
-     * A value of -1 indicates unset, use default.
-     */
-    protected int maxSessionTimeout = -1;
-
-    /**
-     * The ZooKeeper server's socket backlog length. The number of connections
-     * that will be queued to be read before new connections are dropped. A
-     * value of one indicates the default backlog will be used.
-     */
-    protected int clientPortListenBacklog = -1;
-
-    /**
-     * The number of ticks that the initial synchronization phase can take
-     */
-    protected volatile int initLimit;
-
-    /**
-     * The number of ticks that can pass between sending a request and getting
-     * an acknowledgment
-     */
-    protected volatile int syncLimit;
-
-    /**
-     * The number of ticks that can pass before retrying to connect to learner master
-     */
-    protected volatile int connectToLearnerMasterLimit;
-
-    /**
-     * Enables/Disables sync request processor. This option is enabled
-     * by default and is to be used with observers.
-     */
-    protected boolean syncEnabled = true;
-
-    /**
-     * The current tick
-     */
-    protected AtomicInteger tick = new AtomicInteger();
-
-    /**
-     * Whether or not to listen on all IPs for the two quorum ports
-     * (broadcast and fast leader election).
-     */
-    protected boolean quorumListenOnAllIPs = false;
-
-    /**
-     * Keeps time taken for leader election in milliseconds. Sets the value to
-     * this variable only after the completion of leader election.
-     */
-    private long electionTimeTaken = -1;
-
-    /**
-     * Enable/Disables quorum authentication using sasl. Defaulting to false.
-     */
-    protected boolean quorumSaslEnableAuth;
-
-    /**
-     * If this is false, quorum peer server will accept another quorum peer client
-     * connection even if the authentication did not succeed. This can be used while
-     * upgrading ZooKeeper server. Defaulting to false (required).
-     */
-    protected boolean quorumServerSaslAuthRequired;
-
-    /**
-     * If this is false, quorum peer learner will talk to quorum peer server
-     * without authentication. This can be used while upgrading ZooKeeper
-     * server. Defaulting to false (required).
-     */
-    protected boolean quorumLearnerSaslAuthRequired;
-
-    /**
-     * Kerberos quorum service principal. Defaulting to 'zkquorum/localhost'.
-     */
-    protected String quorumServicePrincipal;
-
-    /**
-     * Quorum learner login context name in jaas-conf file to read the kerberos
-     * security details. Defaulting to 'QuorumLearner'.
-     */
-    protected String quorumLearnerLoginContext;
-
-    /**
-     * Quorum server login context name in jaas-conf file to read the kerberos
-     * security details. Defaulting to 'QuorumServer'.
-     */
-    protected String quorumServerLoginContext;
-
-    // TODO: need to tune the default value of thread size
-    private static final int QUORUM_CNXN_THREADS_SIZE_DEFAULT_VALUE = 20;
-    /**
-     * The maximum number of threads to allow in the connectionExecutors thread
-     * pool which will be used to initiate quorum server connections.
-     */
-    protected int quorumCnxnThreadsSize = QUORUM_CNXN_THREADS_SIZE_DEFAULT_VALUE;
-
-    public static final String QUORUM_CNXN_TIMEOUT_MS = "zookeeper.quorumCnxnTimeoutMs";
-    private static int quorumCnxnTimeoutMs;
-
-    static {
-        quorumCnxnTimeoutMs = Integer.getInteger(QUORUM_CNXN_TIMEOUT_MS, -1);
-        LOG.info("{}={}", QUORUM_CNXN_TIMEOUT_MS, quorumCnxnTimeoutMs);
-    }
-
-    /**
-     * @deprecated As of release 3.4.0, this class has been deprecated, since
-     * it is used with one of the udp-based versions of leader election, which
-     * we are also deprecating.
-     *
-     * This class simply responds to requests for the current leader of this
-     * node.
-     * <p>
-     * The request contains just an xid generated by the requestor.
-     * <p>
-     * The response has the xid, the id of this server, the id of the leader,
-     * and the zxid of the leader.
-     *
-     *
-     */
-    @Deprecated
-    class ResponderThread extends ZooKeeperThread {
-
-        ResponderThread() {
-            super("ResponderThread");
-        }
-
-        volatile boolean running = true;
-
-        @Override
-        public void run() {
-            try {
-                byte[] b = new byte[36];
-                ByteBuffer responseBuffer = ByteBuffer.wrap(b);
-                DatagramPacket packet = new DatagramPacket(b, b.length);
-                while (running) {
-                    udpSocket.receive(packet);
-                    if (packet.getLength() != 4) {
-                        LOG.warn("Got more than just an xid! Len = {}", packet.getLength());
-                    } else {
-                        responseBuffer.clear();
-                        responseBuffer.getInt(); // Skip the xid
-                        responseBuffer.putLong(myid);
-                        Vote current = getCurrentVote();
-                        switch (getPeerState()) {
-                        case LOOKING:
-                            responseBuffer.putLong(current.getId());
-                            responseBuffer.putLong(current.getZxid());
-                            break;
-                        case LEADING:
-                            responseBuffer.putLong(myid);
-                            try {
-                                long proposed;
-                                synchronized (leader) {
-                                    proposed = leader.lastProposed;
-                                }
-                                responseBuffer.putLong(proposed);
-                            } catch (NullPointerException npe) {
-                                // This can happen in state transitions,
-                                // just ignore the request
-                            }
-                            break;
-                        case FOLLOWING:
-                            responseBuffer.putLong(current.getId());
-                            try {
-                                responseBuffer.putLong(follower.getZxid());
-                            } catch (NullPointerException npe) {
-                                // This can happen in state transitions,
-                                // just ignore the request
-                            }
-                            break;
-                        case OBSERVING:
-                            // Do nothing, Observers keep themselves to
-                            // themselves.
-                            break;
-                        }
-                        packet.setData(b);
-                        udpSocket.send(packet);
-                    }
-                    packet.setLength(b.length);
-                }
-            } catch (RuntimeException e) {
-                LOG.warn("Unexpected runtime exception in ResponderThread", e);
-            } catch (IOException e) {
-                LOG.warn("Unexpected IO exception in ResponderThread", e);
-            } finally {
-                LOG.warn("QuorumPeer responder thread exited");
-            }
-        }
-
-    }
-
-    private ServerState state = ServerState.LOOKING;
-
-    private AtomicReference<ZabState> zabState = new AtomicReference<>(ZabState.ELECTION);
-    private AtomicReference<SyncMode> syncMode = new AtomicReference<>(SyncMode.NONE);
-    private AtomicReference<String> leaderAddress = new AtomicReference<>("");
-    private AtomicLong leaderId = new AtomicLong(-1);
-
-    private boolean reconfigFlag = false; // indicates that a reconfig just committed
-
-    public synchronized void setPeerState(ServerState newState) {
-        state = newState;
-        if (newState == ServerState.LOOKING) {
-            setLeaderAddressAndId(null, -1);
-            setZabState(ZabState.ELECTION);
-        } else {
-            LOG.info("Peer state changed: {}", getDetailedPeerState());
-        }
-    }
-
-    public void setZabState(ZabState zabState) {
-        if ((zabState == ZabState.BROADCAST) && (unavailableStartTime != 0)) {
-            long unavailableTime = Time.currentElapsedTime() - unavailableStartTime;
-            ServerMetrics.getMetrics().UNAVAILABLE_TIME.add(unavailableTime);
-            if (getPeerState() == ServerState.LEADING) {
-                ServerMetrics.getMetrics().LEADER_UNAVAILABLE_TIME.add(unavailableTime);
-            }
-            unavailableStartTime = 0;
-        }
-        this.zabState.set(zabState);
-        LOG.info("Peer state changed: {}", getDetailedPeerState());
-    }
-
-    public void setSyncMode(SyncMode syncMode) {
-        this.syncMode.set(syncMode);
-        LOG.info("Peer state changed: {}", getDetailedPeerState());
-    }
-
-    public ZabState getZabState() {
-        return zabState.get();
-    }
-
-    public SyncMode getSyncMode() {
-        return syncMode.get();
-    }
-
-    public void setLeaderAddressAndId(MultipleAddresses addr, long newId) {
-        if (addr != null) {
-            leaderAddress.set(String.join("|", addr.getAllHostStrings()));
-        } else {
-            leaderAddress.set(null);
-        }
-        leaderId.set(newId);
-    }
-
-    public String getLeaderAddress() {
-        return leaderAddress.get();
-    }
-
-    public long getLeaderId() {
-        return leaderId.get();
-    }
-
-    public String getDetailedPeerState() {
-        final StringBuilder sb = new StringBuilder(getPeerState().toString().toLowerCase());
-        final ZabState zabState = getZabState();
-        if (!ZabState.ELECTION.equals(zabState)) {
-            sb.append(" - ").append(zabState.toString().toLowerCase());
-        }
-        final SyncMode syncMode = getSyncMode();
-        if (!SyncMode.NONE.equals(syncMode)) {
-            sb.append(" - ").append(syncMode.toString().toLowerCase());
-        }
-        return sb.toString();
-    }
-
-    public synchronized void reconfigFlagSet() {
-        reconfigFlag = true;
-    }
-    public synchronized void reconfigFlagClear() {
-        reconfigFlag = false;
-    }
-    public synchronized boolean isReconfigStateChange() {
-        return reconfigFlag;
-    }
-    public synchronized ServerState getPeerState() {
-        return state;
-    }
-
-    DatagramSocket udpSocket;
-
-    private final AtomicReference<AddressTuple> myAddrs = new AtomicReference<>();
-
-    /**
-     * Resolves hostname for a given server ID.
-     *
-     * This method resolves hostname for a given server ID in both quorumVerifer
-     * and lastSeenQuorumVerifier. If the server ID matches the local server ID,
-     * it also updates myAddrs.
-     */
-    public void recreateSocketAddresses(long id) {
-        QuorumVerifier qv = getQuorumVerifier();
-        if (qv != null) {
-            QuorumServer qs = qv.getAllMembers().get(id);
-            if (qs != null) {
-                qs.recreateSocketAddresses();
-                if (id == getMyId()) {
-                    setAddrs(qs.addr, qs.electionAddr, qs.clientAddr);
-                }
-            }
-        }
-        qv = getLastSeenQuorumVerifier();
-        if (qv != null) {
-            QuorumServer qs = qv.getAllMembers().get(id);
-            if (qs != null) {
-                qs.recreateSocketAddresses();
-            }
-        }
-    }
-
-    private AddressTuple getAddrs() {
-        AddressTuple addrs = myAddrs.get();
-        if (addrs != null) {
-            return addrs;
-        }
-        try {
-            synchronized (QV_LOCK) {
-                addrs = myAddrs.get();
-                while (addrs == null) {
-                    QV_LOCK.wait();
-                    addrs = myAddrs.get();
-                }
-                return addrs;
-            }
-        } catch (InterruptedException e) {
-            Thread.currentThread().interrupt();
-            throw new RuntimeException(e);
-        }
-    }
-
-    public MultipleAddresses getQuorumAddress() {
-        return getAddrs().quorumAddr;
-    }
-
-    public MultipleAddresses getElectionAddress() {
-        return getAddrs().electionAddr;
-    }
-
-    public InetSocketAddress getClientAddress() {
-        final AddressTuple addrs = myAddrs.get();
-        return (addrs == null) ? null : addrs.clientAddr;
-    }
-
-    private void setAddrs(MultipleAddresses quorumAddr, MultipleAddresses electionAddr, InetSocketAddress clientAddr) {
-        synchronized (QV_LOCK) {
-            myAddrs.set(new AddressTuple(quorumAddr, electionAddr, clientAddr));
-            QV_LOCK.notifyAll();
-        }
-    }
-
-    private int electionType;
-
-    Election electionAlg;
-
-    ServerCnxnFactory cnxnFactory;
-    ServerCnxnFactory secureCnxnFactory;
-
-    private FileTxnSnapLog logFactory = null;
-
-    private final QuorumStats quorumStats;
-
-    AdminServer adminServer;
-
-    private final boolean reconfigEnabled;
-
-    public static QuorumPeer testingQuorumPeer() throws SaslException {
-        return new QuorumPeer();
-    }
-
-    public QuorumPeer() throws SaslException {
-        super("QuorumPeer");
-        quorumStats = new QuorumStats(this);
-        jmxRemotePeerBean = new HashMap<>();
-        adminServer = AdminServerFactory.createAdminServer();
-        x509Util = createX509Util();
-        initialize();
-        reconfigEnabled = QuorumPeerConfig.isReconfigEnabled();
-    }
-
-    // VisibleForTesting
-    QuorumX509Util createX509Util() {
-        return new QuorumX509Util();
-    }
-
-    /**
-     * For backward compatibility purposes, we instantiate QuorumMaj by default.
-     */
-
-    public QuorumPeer(Map<Long, QuorumServer> quorumPeers, File dataDir, File dataLogDir, int electionType, long myid, int tickTime, int initLimit, int syncLimit, int connectToLearnerMasterLimit, ServerCnxnFactory cnxnFactory) throws IOException {
-        this(quorumPeers, dataDir, dataLogDir, electionType, myid, tickTime, initLimit, syncLimit, connectToLearnerMasterLimit, false, cnxnFactory, new QuorumMaj(quorumPeers));
-    }
-
-    public QuorumPeer(Map<Long, QuorumServer> quorumPeers, File dataDir, File dataLogDir, int electionType, long myid, int tickTime, int initLimit, int syncLimit, int connectToLearnerMasterLimit, boolean quorumListenOnAllIPs, ServerCnxnFactory cnxnFactory, QuorumVerifier quorumConfig) throws IOException {
-        this();
-        this.cnxnFactory = cnxnFactory;
-        this.electionType = electionType;
-        this.myid = myid;
-        this.tickTime = tickTime;
-        this.initLimit = initLimit;
-        this.syncLimit = syncLimit;
-        this.connectToLearnerMasterLimit = connectToLearnerMasterLimit;
-        this.quorumListenOnAllIPs = quorumListenOnAllIPs;
-        this.logFactory = new FileTxnSnapLog(dataLogDir, dataDir);
-        this.zkDb = new ZKDatabase(this.logFactory);
-        if (quorumConfig == null) {
-            quorumConfig = new QuorumMaj(quorumPeers);
-        }
-        setQuorumVerifier(quorumConfig, false);
-        adminServer = AdminServerFactory.createAdminServer();
-    }
-
-    public void initialize() throws SaslException {
-        // init quorum auth server & learner
-        if (isQuorumSaslAuthEnabled()) {
-            Set<String> authzHosts = new HashSet<>();
-            for (QuorumServer qs : getView().values()) {
-                authzHosts.add(qs.hostname);
-            }
-            authServer = new SaslQuorumAuthServer(isQuorumServerSaslAuthRequired(), quorumServerLoginContext, authzHosts);
-            authLearner = new SaslQuorumAuthLearner(isQuorumLearnerSaslAuthRequired(), quorumServicePrincipal, quorumLearnerLoginContext);
-        } else {
-            authServer = new NullQuorumAuthServer();
-            authLearner = new NullQuorumAuthLearner();
-        }
-    }
-
-    QuorumStats quorumStats() {
-        return quorumStats;
-    }
-
-    @Override
-    public synchronized void start() {
-        if (!getView().containsKey(myid)) {
-            throw new RuntimeException("My id " + myid + " not in the peer list");
-        }
-        loadDataBase();
-        startServerCnxnFactory();
-        try {
-            adminServer.start();
-        } catch (AdminServerException e) {
-            LOG.warn("Problem starting AdminServer", e);
-        }
-        startLeaderElection();
-        startJvmPauseMonitor();
-        super.start();
-    }
-
-    private void loadDataBase() {
-        try {
-            zkDb.loadDataBase();
-
-            // load the epochs
-            long lastProcessedZxid = zkDb.getDataTree().lastProcessedZxid;
-            long epochOfZxid = ZxidUtils.getEpochFromZxid(lastProcessedZxid);
-            try {
-                currentEpoch = readLongFromFile(CURRENT_EPOCH_FILENAME);
-            } catch (FileNotFoundException e) {
-                // pick a reasonable epoch number
-                // this should only happen once when moving to a
-                // new code version
-                currentEpoch = epochOfZxid;
-                LOG.info(
-                    "{} not found! Creating with a reasonable default of {}. "
-                        + "This should only happen when you are upgrading your installation",
-                    CURRENT_EPOCH_FILENAME,
-                    currentEpoch);
-                writeLongToFile(CURRENT_EPOCH_FILENAME, currentEpoch);
-            }
-            if (epochOfZxid > currentEpoch) {
-                // acceptedEpoch.tmp file in snapshot directory
-                File currentTmp = new File(getTxnFactory().getSnapDir(),
-                    CURRENT_EPOCH_FILENAME + AtomicFileOutputStream.TMP_EXTENSION);
-                if (currentTmp.exists()) {
-                    long epochOfTmp = readLongFromFile(currentTmp.getName());
-                    LOG.info("{} found. Setting current epoch to {}.", currentTmp, epochOfTmp);
-                    setCurrentEpoch(epochOfTmp);
-                } else {
-                    throw new IOException(
-                        "The current epoch, " + ZxidUtils.zxidToString(currentEpoch)
-                            + ", is older than the last zxid, " + lastProcessedZxid);
-                }
-            }
-            try {
-                acceptedEpoch = readLongFromFile(ACCEPTED_EPOCH_FILENAME);
-            } catch (FileNotFoundException e) {
-                // pick a reasonable epoch number
-                // this should only happen once when moving to a
-                // new code version
-                acceptedEpoch = epochOfZxid;
-                LOG.info(
-                    "{} not found! Creating with a reasonable default of {}. "
-                        + "This should only happen when you are upgrading your installation",
-                    ACCEPTED_EPOCH_FILENAME,
-                    acceptedEpoch);
-                writeLongToFile(ACCEPTED_EPOCH_FILENAME, acceptedEpoch);
-            }
-            if (acceptedEpoch < currentEpoch) {
-                throw new IOException("The accepted epoch, "
-                                      + ZxidUtils.zxidToString(acceptedEpoch)
-                                      + " is less than the current epoch, "
-                                      + ZxidUtils.zxidToString(currentEpoch));
-            }
-        } catch (IOException ie) {
-            LOG.error("Unable to load database on disk", ie);
-            throw new RuntimeException("Unable to run quorum server ", ie);
-        }
-    }
-
-    ResponderThread responder;
-
-    public synchronized void stopLeaderElection() {
-        responder.running = false;
-        responder.interrupt();
-    }
-    public synchronized void startLeaderElection() {
-        try {
-            if (getPeerState() == ServerState.LOOKING) {
-                currentVote = new Vote(myid, getLastLoggedZxid(), getCurrentEpoch());
-            }
-        } catch (IOException e) {
-            RuntimeException re = new RuntimeException(e.getMessage());
-            re.setStackTrace(e.getStackTrace());
-            throw re;
-        }
-
-        this.electionAlg = createElectionAlgorithm(electionType);
-    }
-
-    private void startJvmPauseMonitor() {
-        if (this.jvmPauseMonitor != null) {
-            this.jvmPauseMonitor.serviceStart();
-        }
-    }
-
-    /**
-     * Count the number of nodes in the map that could be followers.
-     * @param peers
-     * @return The number of followers in the map
-     */
-    protected static int countParticipants(Map<Long, QuorumServer> peers) {
-        int count = 0;
-        for (QuorumServer q : peers.values()) {
-            if (q.type == LearnerType.PARTICIPANT) {
-                count++;
-            }
-        }
-        return count;
-    }
-
-    /**
-     * This constructor is only used by the existing unit test code.
-     * It defaults to FileLogProvider persistence provider.
-     */
-    public QuorumPeer(Map<Long, QuorumServer> quorumPeers, File snapDir, File logDir, int clientPort, int electionAlg, long myid, int tickTime, int initLimit, int syncLimit, int connectToLearnerMasterLimit) throws IOException {
-        this(
-            quorumPeers,
-            snapDir,
-            logDir,
-            electionAlg,
-            myid,
-            tickTime,
-            initLimit,
-            syncLimit,
-            connectToLearnerMasterLimit,
-            false,
-            ServerCnxnFactory.createFactory(getClientAddress(quorumPeers, myid, clientPort), -1),
-            new QuorumMaj(quorumPeers));
-    }
-
-    public QuorumPeer(Map<Long, QuorumServer> quorumPeers, File snapDir, File logDir, int clientPort, int electionAlg, long myid, int tickTime, int initLimit, int syncLimit, int connectToLearnerMasterLimit, String oraclePath) throws IOException {
-        this(
-                quorumPeers,
-                snapDir,
-                logDir,
-                electionAlg,
-                myid,
-                tickTime,
-                initLimit,
-                syncLimit,
-                connectToLearnerMasterLimit,
-                false,
-                ServerCnxnFactory.createFactory(getClientAddress(quorumPeers, myid, clientPort), -1),
-                new QuorumOracleMaj(quorumPeers, oraclePath));
-    }
-
-    /**
-     * This constructor is only used by the existing unit test code.
-     * It defaults to FileLogProvider persistence provider.
-     */
-    public QuorumPeer(Map<Long, QuorumServer> quorumPeers, File snapDir, File logDir, int clientPort, int electionAlg, long myid, int tickTime, int initLimit, int syncLimit, int connectToLearnerMasterLimit, QuorumVerifier quorumConfig) throws IOException {
-        this(
-            quorumPeers,
-            snapDir,
-            logDir,
-            electionAlg,
-            myid,
-            tickTime,
-            initLimit,
-            syncLimit,
-            connectToLearnerMasterLimit,
-            false,
-            ServerCnxnFactory.createFactory(getClientAddress(quorumPeers, myid, clientPort), -1),
-            quorumConfig);
-    }
-
-    private static InetSocketAddress getClientAddress(Map<Long, QuorumServer> quorumPeers, long myid, int clientPort) throws IOException {
-        QuorumServer quorumServer = quorumPeers.get(myid);
-        if (null == quorumServer) {
-            throw new IOException("No QuorumServer correspoding to myid " + myid);
-        }
-        if (null == quorumServer.clientAddr) {
-            return new InetSocketAddress(clientPort);
-        }
-        if (quorumServer.clientAddr.getPort() != clientPort) {
-            throw new IOException("QuorumServer port "
-                                  + quorumServer.clientAddr.getPort()
-                                  + " does not match with given port "
-                                  + clientPort);
-        }
-        return quorumServer.clientAddr;
-    }
-
-    /**
-     * returns the highest zxid that this host has seen
-     *
-     * @return the highest zxid for this host
-     */
-    public long getLastLoggedZxid() {
-        if (!zkDb.isInitialized()) {
-            loadDataBase();
-        }
-        return zkDb.getDataTreeLastProcessedZxid();
-    }
-
-    public Follower follower;
-    public Leader leader;
-    public Observer observer;
-
-    protected Follower makeFollower(FileTxnSnapLog logFactory) throws IOException {
-        return new Follower(this, new FollowerZooKeeperServer(logFactory, this, this.zkDb));
-    }
-
-    protected Leader makeLeader(FileTxnSnapLog logFactory) throws IOException, X509Exception {
-        return new Leader(this, new LeaderZooKeeperServer(logFactory, this, this.zkDb));
-    }
-
-    protected Observer makeObserver(FileTxnSnapLog logFactory) throws IOException {
-        return new Observer(this, new ObserverZooKeeperServer(logFactory, this, this.zkDb));
-    }
-
-    @SuppressWarnings("deprecation")
-    protected Election createElectionAlgorithm(int electionAlgorithm) {
-        Election le = null;
-
-        //TODO: use a factory rather than a switch
-        switch (electionAlgorithm) {
-        case 1:
-            throw new UnsupportedOperationException("Election Algorithm 1 is not supported.");
-        case 2:
-            throw new UnsupportedOperationException("Election Algorithm 2 is not supported.");
-        case 3:
-            QuorumCnxManager qcm = createCnxnManager();
-            QuorumCnxManager oldQcm = qcmRef.getAndSet(qcm);
-            if (oldQcm != null) {
-                LOG.warn("Clobbering already-set QuorumCnxManager (restarting leader election?)");
-                oldQcm.halt();
-            }
-            QuorumCnxManager.Listener listener = qcm.listener;
-            if (listener != null) {
-                listener.start();
-                FastLeaderElection fle = new FastLeaderElection(this, qcm);
-                fle.start();
-                le = fle;
-            } else {
-                LOG.error("Null listener when initializing cnx manager");
-            }
-            break;
-        default:
-            assert false;
-        }
-        return le;
-    }
-
-    @SuppressWarnings("deprecation")
-    protected Election makeLEStrategy() {
-        LOG.debug("Initializing leader election protocol...");
-        return electionAlg;
-    }
-
-    protected synchronized void setLeader(Leader newLeader) {
-        leader = newLeader;
-    }
-
-    protected synchronized void setFollower(Follower newFollower) {
-        follower = newFollower;
-    }
-
-    protected synchronized void setObserver(Observer newObserver) {
-        observer = newObserver;
-    }
-
-    public synchronized ZooKeeperServer getActiveServer() {
-        if (leader != null) {
-            return leader.zk;
-        } else if (follower != null) {
-            return follower.zk;
-        } else if (observer != null) {
-            return observer.zk;
-        }
-        return null;
-    }
-
-    boolean shuttingDownLE = false;
-
-    public void setSuspended(boolean suspended) {
-        this.suspended.set(suspended);
-    }
-    private void checkSuspended() {
-        try {
-            while (suspended.get()) {
-                Thread.sleep(10);
-            }
-        } catch (InterruptedException err) {
-            Thread.currentThread().interrupt();
-        }
-    }
-
-    @Override
-    public void run() {
-        updateThreadName();
-
-        LOG.debug("Starting quorum peer");
-        try {
-            jmxQuorumBean = new QuorumBean(this);
-            MBeanRegistry.getInstance().register(jmxQuorumBean, null);
-            for (QuorumServer s : getView().values()) {
-                ZKMBeanInfo p;
-                if (getMyId() == s.id) {
-                    p = jmxLocalPeerBean = new LocalPeerBean(this);
-                    try {
-                        MBeanRegistry.getInstance().register(p, jmxQuorumBean);
-                    } catch (Exception e) {
-                        LOG.warn("Failed to register with JMX", e);
-                        jmxLocalPeerBean = null;
-                    }
-                } else {
-                    RemotePeerBean rBean = new RemotePeerBean(this, s);
-                    try {
-                        MBeanRegistry.getInstance().register(rBean, jmxQuorumBean);
-                        jmxRemotePeerBean.put(s.id, rBean);
-                    } catch (Exception e) {
-                        LOG.warn("Failed to register with JMX", e);
-                    }
-                }
-            }
-        } catch (Exception e) {
-            LOG.warn("Failed to register with JMX", e);
-            jmxQuorumBean = null;
-        }
-
-        try {
-            /*
-             * Main loop
-             */
-            while (running) {
-                if (unavailableStartTime == 0) {
-                    unavailableStartTime = Time.currentElapsedTime();
-                }
-
-                switch (getPeerState()) {
-                case LOOKING:
-                    LOG.info("LOOKING");
-                    ServerMetrics.getMetrics().LOOKING_COUNT.add(1);
-
-                    if (Boolean.getBoolean("readonlymode.enabled")) {
-                        LOG.info("Attempting to start ReadOnlyZooKeeperServer");
-
-                        // Create read-only server but don't start it immediately
-                        final ReadOnlyZooKeeperServer roZk = new ReadOnlyZooKeeperServer(logFactory, this, this.zkDb);
-
-                        // Instead of starting roZk immediately, wait some grace
-                        // period before we decide we're partitioned.
-                        //
-                        // Thread is used here because otherwise it would require
-                        // changes in each of election strategy classes which is
-                        // unnecessary code coupling.
-                        Thread roZkMgr = new Thread() {
-                            public void run() {
-                                try {
-                                    // lower-bound grace period to 2 secs
-                                    sleep(Math.max(2000, tickTime));
-                                    if (ServerState.LOOKING.equals(getPeerState())) {
-                                        roZk.startup();
-                                    }
-                                } catch (InterruptedException e) {
-                                    LOG.info("Interrupted while attempting to start ReadOnlyZooKeeperServer, not started");
-                                } catch (Exception e) {
-                                    LOG.error("FAILED to start ReadOnlyZooKeeperServer", e);
-                                }
-                            }
-                        };
-                        try {
-                            roZkMgr.start();
-                            reconfigFlagClear();
-                            if (shuttingDownLE) {
-                                shuttingDownLE = false;
-                                startLeaderElection();
-                            }
-                            setCurrentVote(makeLEStrategy().lookForLeader());
-                            checkSuspended();
-                        } catch (Exception e) {
-                            LOG.warn("Unexpected exception", e);
-                            setPeerState(ServerState.LOOKING);
-                        } finally {
-                            // If the thread is in the the grace period, interrupt
-                            // to come out of waiting.
-                            roZkMgr.interrupt();
-                            roZk.shutdown();
-                        }
-                    } else {
-                        try {
-                            reconfigFlagClear();
-                            if (shuttingDownLE) {
-                                shuttingDownLE = false;
-                                startLeaderElection();
-                            }
-                            setCurrentVote(makeLEStrategy().lookForLeader());
-                        } catch (Exception e) {
-                            LOG.warn("Unexpected exception", e);
-                            setPeerState(ServerState.LOOKING);
-                        }
-                    }
-                    break;
-                case OBSERVING:
-                    try {
-                        LOG.info("OBSERVING");
-                        setObserver(makeObserver(logFactory));
-                        observer.observeLeader();
-                    } catch (Exception e) {
-                        LOG.warn("Unexpected exception", e);
-                    } finally {
-                        observer.shutdown();
-                        setObserver(null);
-                        updateServerState();
-
-                        // Add delay jitter before we switch to LOOKING
-                        // state to reduce the load of ObserverMaster
-                        if (isRunning()) {
-                            Observer.waitForObserverElectionDelay();
-                        }
-                    }
-                    break;
-                case FOLLOWING:
-                    try {
-                        LOG.info("FOLLOWING");
-                        setFollower(makeFollower(logFactory));
-                        follower.followLeader();
-                    } catch (Exception e) {
-                        LOG.warn("Unexpected exception", e);
-                    } finally {
-                        follower.shutdown();
-                        setFollower(null);
-                        updateServerState();
-                    }
-                    break;
-                case LEADING:
-                    LOG.info("LEADING");
-                    try {
-                        setLeader(makeLeader(logFactory));
-                        leader.lead();
-                        setLeader(null);
-                    } catch (Exception e) {
-                        LOG.warn("Unexpected exception", e);
-                    } finally {
-                        if (leader != null) {
-                            leader.shutdown("Forcing shutdown");
-                            setLeader(null);
-                        }
-                        updateServerState();
-                    }
-                    break;
-                }
-            }
-        } finally {
-            LOG.warn("QuorumPeer main thread exited");
-            MBeanRegistry instance = MBeanRegistry.getInstance();
-            instance.unregister(jmxQuorumBean);
-            instance.unregister(jmxLocalPeerBean);
-
-            for (RemotePeerBean remotePeerBean : jmxRemotePeerBean.values()) {
-                instance.unregister(remotePeerBean);
-            }
-
-            jmxQuorumBean = null;
-            jmxLocalPeerBean = null;
-            jmxRemotePeerBean = null;
-        }
-    }
-
-    private synchronized void updateServerState() {
-        if (!reconfigFlag) {
-            setPeerState(ServerState.LOOKING);
-            LOG.warn("PeerState set to LOOKING");
-            return;
-        }
-
-        if (getMyId() == getCurrentVote().getId()) {
-            setPeerState(ServerState.LEADING);
-            LOG.debug("PeerState set to LEADING");
-        } else if (getLearnerType() == LearnerType.PARTICIPANT) {
-            setPeerState(ServerState.FOLLOWING);
-            LOG.debug("PeerState set to FOLLOWING");
-        } else if (getLearnerType() == LearnerType.OBSERVER) {
-            setPeerState(ServerState.OBSERVING);
-            LOG.debug("PeerState set to OBSERVER");
-        } else { // currently shouldn't happen since there are only 2 learner types
-            setPeerState(ServerState.LOOKING);
-            LOG.debug("Should not be here");
-        }
-        reconfigFlag = false;
-    }
-
-    public void shutdown() {
-        running = false;
-        x509Util.close();
-        if (leader != null) {
-            leader.shutdown("quorum Peer shutdown");
-        }
-        if (follower != null) {
-            follower.shutdown();
-        }
-        shutdownServerCnxnFactory();
-        if (udpSocket != null) {
-            udpSocket.close();
-        }
-        if (jvmPauseMonitor != null) {
-            jvmPauseMonitor.serviceStop();
-        }
-
-        try {
-            adminServer.shutdown();
-        } catch (AdminServerException e) {
-            LOG.warn("Problem stopping AdminServer", e);
-        }
-
-        if (getElectionAlg() != null) {
-            this.interrupt();
-            getElectionAlg().shutdown();
-        }
-        try {
-            zkDb.close();
-        } catch (IOException ie) {
-            LOG.warn("Error closing logs ", ie);
-        }
-    }
-
-    /**
-     * A 'view' is a node's current opinion of the membership of the entire
-     * ensemble.
-     */
-    public Map<Long, QuorumPeer.QuorumServer> getView() {
-        return Collections.unmodifiableMap(getQuorumVerifier().getAllMembers());
-    }
-
-    /**
-     * Observers are not contained in this view, only nodes with
-     * PeerType=PARTICIPANT.
-     */
-    public Map<Long, QuorumPeer.QuorumServer> getVotingView() {
-        return getQuorumVerifier().getVotingMembers();
-    }
-
-    /**
-     * Returns only observers, no followers.
-     */
-    public Map<Long, QuorumPeer.QuorumServer> getObservingView() {
-        return getQuorumVerifier().getObservingMembers();
-    }
-
-    public synchronized Set<Long> getCurrentAndNextConfigVoters() {
-        Set<Long> voterIds = new HashSet<>(getQuorumVerifier().getVotingMembers().keySet());
-        if (getLastSeenQuorumVerifier() != null) {
-            voterIds.addAll(getLastSeenQuorumVerifier().getVotingMembers().keySet());
-        }
-        return voterIds;
-    }
-
-    /**
-     * Check if a node is in the current view. With static membership, the
-     * result of this check will never change; only when dynamic membership
-     * is introduced will this be more useful.
-     */
-    public boolean viewContains(Long sid) {
-        return this.getView().containsKey(sid);
-    }
-
-    /**
-     * Only used by QuorumStats at the moment
-     */
-    public String[] getQuorumPeers() {
-        List<String> l = new ArrayList<>();
-        synchronized (this) {
-            if (leader != null) {
-                for (LearnerHandler fh : leader.getLearners()) {
-                    if (fh.getSocket() != null) {
-                        String s = formatInetAddr((InetSocketAddress) fh.getSocket().getRemoteSocketAddress());
-                        if (leader.isLearnerSynced(fh)) {
-                            s += "*";
-                        }
-                        l.add(s);
-                    }
-                }
-            } else if (follower != null) {
-                l.add(formatInetAddr((InetSocketAddress) follower.sock.getRemoteSocketAddress()));
-            }
-        }
-        return l.toArray(new String[0]);
-    }
-
-    public String getServerState() {
-        switch (getPeerState()) {
-        case LOOKING:
-            return QuorumStats.Provider.LOOKING_STATE;
-        case LEADING:
-            return QuorumStats.Provider.LEADING_STATE;
-        case FOLLOWING:
-            return QuorumStats.Provider.FOLLOWING_STATE;
-        case OBSERVING:
-            return QuorumStats.Provider.OBSERVING_STATE;
-        }
-        return QuorumStats.Provider.UNKNOWN_STATE;
-    }
-
-    /**
-     * set the id of this quorum peer.
-     */
-    public void setMyid(long myid) {
-        this.myid = myid;
-    }
-
-    public void setInitialConfig(String initialConfig) {
-        this.initialConfig = initialConfig;
-    }
-
-    public String getInitialConfig() {
-        return initialConfig;
-    }
-
-    /**
-     * Get the number of milliseconds of each tick
-     */
-    public int getTickTime() {
-        return tickTime;
-    }
-
-    /**
-     * Set the number of milliseconds of each tick
-     */
-    public void setTickTime(int tickTime) {
-        LOG.info("tickTime set to {}", tickTime);
-        this.tickTime = tickTime;
-    }
-
-    /** Maximum number of connections allowed from particular host (ip) */
-    public int getMaxClientCnxnsPerHost() {
-        if (cnxnFactory != null) {
-            return cnxnFactory.getMaxClientCnxnsPerHost();
-        }
-        if (secureCnxnFactory != null) {
-            return secureCnxnFactory.getMaxClientCnxnsPerHost();
-        }
-        return -1;
-    }
-
-    /** Whether local sessions are enabled */
-    public boolean areLocalSessionsEnabled() {
-        return localSessionsEnabled;
-    }
-
-    /** Whether to enable local sessions */
-    public void enableLocalSessions(boolean flag) {
-        LOG.info("Local sessions {}", (flag ? "enabled" : "disabled"));
-        localSessionsEnabled = flag;
-    }
-
-    /** Whether local sessions are allowed to upgrade to global sessions */
-    public boolean isLocalSessionsUpgradingEnabled() {
-        return localSessionsUpgradingEnabled;
-    }
-
-    /** Whether to allow local sessions to upgrade to global sessions */
-    public void enableLocalSessionsUpgrading(boolean flag) {
-        LOG.info("Local session upgrading {}", (flag ? "enabled" : "disabled"));
-        localSessionsUpgradingEnabled = flag;
-    }
-
-    /** minimum session timeout in milliseconds */
-    public int getMinSessionTimeout() {
-        return minSessionTimeout;
-    }
-
-    /** minimum session timeout in milliseconds */
-    public void setMinSessionTimeout(int min) {
-        LOG.info("minSessionTimeout set to {}", min);
-        this.minSessionTimeout = min;
-    }
-
-    /** maximum session timeout in milliseconds */
-    public int getMaxSessionTimeout() {
-        return maxSessionTimeout;
-    }
-
-    /** maximum session timeout in milliseconds */
-    public void setMaxSessionTimeout(int max) {
-        LOG.info("maxSessionTimeout set to {}", max);
-        this.maxSessionTimeout = max;
-    }
-
-    /** The server socket's listen backlog length */
-    public int getClientPortListenBacklog() {
-        return this.clientPortListenBacklog;
-    }
-
-    /** Sets the server socket's listen backlog length. */
-    public void setClientPortListenBacklog(int backlog) {
-        this.clientPortListenBacklog = backlog;
-    }
-
-    /**
-     * Get the number of ticks that the initial synchronization phase can take
-     */
-    public int getInitLimit() {
-        return initLimit;
-    }
-
-    /**
-     * Set the number of ticks that the initial synchronization phase can take
-     */
-    public void setInitLimit(int initLimit) {
-        LOG.info("initLimit set to {}", initLimit);
-        this.initLimit = initLimit;
-    }
-
-    /**
-     * Get the current tick
-     */
-    public int getTick() {
-        return tick.get();
-    }
-
-    public QuorumVerifier configFromString(String s) throws IOException, ConfigException {
-        Properties props = new Properties();
-        props.load(new StringReader(s));
-        return QuorumPeerConfig.parseDynamicConfig(props, electionType, false, false, getQuorumVerifier().getOraclePath());
-    }
-
-    /**
-     * Return QuorumVerifier object for the last committed configuration.
-     */
-    public QuorumVerifier getQuorumVerifier() {
-        synchronized (QV_LOCK) {
-            return quorumVerifier;
-        }
-    }
-
-    /**
-     * Return QuorumVerifier object for the last proposed configuration.
-     */
-    public QuorumVerifier getLastSeenQuorumVerifier() {
-        synchronized (QV_LOCK) {
-            return lastSeenQuorumVerifier;
-        }
-    }
-
-    public synchronized void restartLeaderElection(QuorumVerifier qvOLD, QuorumVerifier qvNEW) {
-        if (qvOLD == null || !qvOLD.equals(qvNEW)) {
-            LOG.warn("Restarting Leader Election");
-            getElectionAlg().shutdown();
-            shuttingDownLE = false;
-            startLeaderElection();
-        }
-    }
-
-    public String getNextDynamicConfigFilename() {
-        if (configFilename == null) {
-            LOG.warn("configFilename is null! This should only happen in tests.");
-            return null;
-        }
-        return configFilename + QuorumPeerConfig.nextDynamicConfigFileSuffix;
-    }
-
-    // On entry to this method, qcm must be non-null and the locks on both qcm and QV_LOCK
-    // must be held.  We don't want quorumVerifier/lastSeenQuorumVerifier to change out from
-    // under us, so we have to hold QV_LOCK; and since the call to qcm.connectOne() will take
-    // the lock on qcm (and take QV_LOCK again inside that), the caller needs to have taken
-    // qcm outside QV_LOCK to avoid a deadlock against other callers of qcm.connectOne().
-    private void connectNewPeers(QuorumCnxManager qcm) {
-        if (quorumVerifier != null && lastSeenQuorumVerifier != null) {
-            Map<Long, QuorumServer> committedView = quorumVerifier.getAllMembers();
-            for (Entry<Long, QuorumServer> e : lastSeenQuorumVerifier.getAllMembers().entrySet()) {
-                if (e.getKey() != getMyId() && !committedView.containsKey(e.getKey())) {
-                    qcm.connectOne(e.getKey());
-                }
-            }
-        }
-    }
-
-    public void setLastSeenQuorumVerifier(QuorumVerifier qv, boolean writeToDisk) {
-        if (!isReconfigEnabled()) {
-            LOG.info("Dynamic reconfig is disabled, we don't store the last seen config.");
-            return;
-        }
-
-        // If qcm is non-null, we may call qcm.connectOne(), which will take the lock on qcm
-        // and then take QV_LOCK.  Take the locks in the same order to ensure that we don't
-        // deadlock against other callers of connectOne().  If qcmRef gets set in another
-        // thread while we're inside the synchronized block, that does no harm; if we didn't
-        // take a lock on qcm (because it was null when we sampled it), we won't call
-        // connectOne() on it.  (Use of an AtomicReference is enough to guarantee visibility
-        // of updates that provably happen in another thread before entering this method.)
-        QuorumCnxManager qcm = qcmRef.get();
-        Object outerLockObject = (qcm != null) ? qcm : QV_LOCK;
-        synchronized (outerLockObject) {
-            synchronized (QV_LOCK) {
-                if (lastSeenQuorumVerifier != null && lastSeenQuorumVerifier.getVersion() > qv.getVersion()) {
-                    LOG.error("setLastSeenQuorumVerifier called with stale config "
-                              + qv.getVersion()
-                              + ". Current version: "
-                              + quorumVerifier.getVersion());
-                }
-                // assuming that a version uniquely identifies a configuration, so if
-                // version is the same, nothing to do here.
-                if (lastSeenQuorumVerifier != null && lastSeenQuorumVerifier.getVersion() == qv.getVersion()) {
-                    return;
-                }
-                lastSeenQuorumVerifier = qv;
-                if (qcm != null) {
-                    connectNewPeers(qcm);
-                }
-
-                if (writeToDisk) {
-                    try {
-                        String fileName = getNextDynamicConfigFilename();
-                        if (fileName != null) {
-                            QuorumPeerConfig.writeDynamicConfig(fileName, qv, true);
-                        }
-                    } catch (IOException e) {
-                        LOG.error("Error writing next dynamic config file to disk", e);
-                    }
-                }
-            }
-        }
-    }
-
-    public QuorumVerifier setQuorumVerifier(QuorumVerifier qv, boolean writeToDisk) {
-        synchronized (QV_LOCK) {
-            if ((quorumVerifier != null) && (quorumVerifier.getVersion() >= qv.getVersion())) {
-                // this is normal. For example - server found out about new config through FastLeaderElection gossiping
-                // and then got the same config in UPTODATE message so its already known
-                LOG.debug(
-                    "{} setQuorumVerifier called with known or old config {}. Current version: {}",
-                    getMyId(),
-                    qv.getVersion(),
-                    quorumVerifier.getVersion());
-                return quorumVerifier;
-            }
-            QuorumVerifier prevQV = quorumVerifier;
-            quorumVerifier = qv;
-            if (lastSeenQuorumVerifier == null || (qv.getVersion() > lastSeenQuorumVerifier.getVersion())) {
-                lastSeenQuorumVerifier = qv;
-            }
-
-            if (writeToDisk) {
-                // some tests initialize QuorumPeer without a static config file
-                if (configFilename != null) {
-                    try {
-                        String dynamicConfigFilename = makeDynamicConfigFilename(qv.getVersion());
-                        QuorumPeerConfig.writeDynamicConfig(dynamicConfigFilename, qv, false);
-                        QuorumPeerConfig.editStaticConfig(configFilename, dynamicConfigFilename, needEraseClientInfoFromStaticConfig());
-                    } catch (IOException e) {
-                        LOG.error("Error closing file", e);
-                    }
-                } else {
-                    LOG.info("writeToDisk == true but configFilename == null");
-                }
-            }
-
-            if (qv.getVersion() == lastSeenQuorumVerifier.getVersion()) {
-                QuorumPeerConfig.deleteFile(getNextDynamicConfigFilename());
-            }
-            QuorumServer qs = qv.getAllMembers().get(getMyId());
-            if (qs != null) {
-                setAddrs(qs.addr, qs.electionAddr, qs.clientAddr);
-            }
-            updateObserverMasterList();
-            return prevQV;
-        }
-    }
-
-    private String makeDynamicConfigFilename(long version) {
-        return configFilename + ".dynamic." + Long.toHexString(version);
-    }
-
-    private boolean needEraseClientInfoFromStaticConfig() {
-        QuorumServer server = quorumVerifier.getAllMembers().get(getMyId());
-        return (server != null && server.clientAddr != null && !server.isClientAddrFromStatic);
-    }
-
-    /**
-     * Get an instance of LeaderElection
-     */
-    public Election getElectionAlg() {
-        return electionAlg;
-    }
-
-    /**
-     * Get the synclimit
-     */
-    public int getSyncLimit() {
-        return syncLimit;
-    }
-
-    /**
-     * Set the synclimit
-     */
-    public void setSyncLimit(int syncLimit) {
-        LOG.info("syncLimit set to {}", syncLimit);
-        this.syncLimit = syncLimit;
-    }
-
-    /**
-     * Get the connectToLearnerMasterLimit
-     */
-    public int getConnectToLearnerMasterLimit() {
-        return connectToLearnerMasterLimit;
-    }
-
-    /**
-     * Set the connectToLearnerMasterLimit
-     */
-    public void setConnectToLearnerMasterLimit(int connectToLearnerMasterLimit) {
-        LOG.info("connectToLearnerMasterLimit set to {}", connectToLearnerMasterLimit);
-        this.connectToLearnerMasterLimit = connectToLearnerMasterLimit;
-    }
-
-    /**
-     * The syncEnabled can also be set via a system property.
-     */
-    public static final String SYNC_ENABLED = "zookeeper.observer.syncEnabled";
-
-    /**
-     * Return syncEnabled.
-     */
-    public boolean getSyncEnabled() {
-        if (System.getProperty(SYNC_ENABLED) != null) {
-            LOG.info("{}={}", SYNC_ENABLED, Boolean.getBoolean(SYNC_ENABLED));
-            return Boolean.getBoolean(SYNC_ENABLED);
-        } else {
-            return syncEnabled;
-        }
-    }
-
-    /**
-     * Set syncEnabled.
-     *
-     * @param syncEnabled
-     */
-    public void setSyncEnabled(boolean syncEnabled) {
-        this.syncEnabled = syncEnabled;
-    }
-
-    /**
-     * Gets the election type
-     */
-    public int getElectionType() {
-        return electionType;
-    }
-
-    /**
-     * Sets the election type
-     */
-    public void setElectionType(int electionType) {
-        this.electionType = electionType;
-    }
-
-    public boolean getQuorumListenOnAllIPs() {
-        return quorumListenOnAllIPs;
-    }
-
-    public void setQuorumListenOnAllIPs(boolean quorumListenOnAllIPs) {
-        this.quorumListenOnAllIPs = quorumListenOnAllIPs;
-    }
-
-    public void setCnxnFactory(ServerCnxnFactory cnxnFactory) {
-        this.cnxnFactory = cnxnFactory;
-    }
-
-    public void setSecureCnxnFactory(ServerCnxnFactory secureCnxnFactory) {
-        this.secureCnxnFactory = secureCnxnFactory;
-    }
-
-    public void setSslQuorum(boolean sslQuorum) {
-        if (sslQuorum) {
-            LOG.info("Using TLS encrypted quorum communication");
-        } else {
-            LOG.info("Using insecure (non-TLS) quorum communication");
-        }
-        this.sslQuorum = sslQuorum;
-    }
-
-    public void setUsePortUnification(boolean shouldUsePortUnification) {
-        LOG.info("Port unification {}", shouldUsePortUnification ? "enabled" : "disabled");
-        this.shouldUsePortUnification = shouldUsePortUnification;
-    }
-
-    private void startServerCnxnFactory() {
-        if (cnxnFactory != null) {
-            cnxnFactory.start();
-        }
-        if (secureCnxnFactory != null) {
-            secureCnxnFactory.start();
-        }
-    }
-
-    private void shutdownServerCnxnFactory() {
-        if (cnxnFactory != null) {
-            cnxnFactory.shutdown();
-        }
-        if (secureCnxnFactory != null) {
-            secureCnxnFactory.shutdown();
-        }
-    }
-
-    // Leader and learner will control the zookeeper server and pass it into QuorumPeer.
-    public void setZooKeeperServer(ZooKeeperServer zks) {
-        if (cnxnFactory != null) {
-            cnxnFactory.setZooKeeperServer(zks);
-        }
-        if (secureCnxnFactory != null) {
-            secureCnxnFactory.setZooKeeperServer(zks);
-        }
-    }
-
-    public void closeAllConnections() {
-        if (cnxnFactory != null) {
-            cnxnFactory.closeAll(ServerCnxn.DisconnectReason.SERVER_SHUTDOWN);
-        }
-        if (secureCnxnFactory != null) {
-            secureCnxnFactory.closeAll(ServerCnxn.DisconnectReason.SERVER_SHUTDOWN);
-        }
-    }
-
-    public int getClientPort() {
-        if (cnxnFactory != null) {
-            return cnxnFactory.getLocalPort();
-        }
-        return -1;
-    }
-
-    public int getSecureClientPort() {
-        if (secureCnxnFactory != null) {
-            return secureCnxnFactory.getLocalPort();
-        }
-        return -1;
-    }
-
-    public void setTxnFactory(FileTxnSnapLog factory) {
-        this.logFactory = factory;
-    }
-
-    public FileTxnSnapLog getTxnFactory() {
-        return this.logFactory;
-    }
-
-    /**
-     * set zk database for this node
-     * @param database
-     */
-    public void setZKDatabase(ZKDatabase database) {
-        this.zkDb = database;
-    }
-
-    protected ZKDatabase getZkDb() {
-        return zkDb;
-    }
-
-    public synchronized void initConfigInZKDatabase() {
-        if (zkDb != null) {
-            zkDb.initConfigInZKDatabase(getQuorumVerifier());
-        }
-    }
-
-    public boolean isRunning() {
-        return running;
-    }
-
-    /**
-     * get reference to QuorumCnxManager
-     */
-    public QuorumCnxManager getQuorumCnxManager() {
-        return qcmRef.get();
-    }
-    private long readLongFromFile(String name) throws IOException {
-        File file = new File(logFactory.getSnapDir(), name);
-        BufferedReader br = new BufferedReader(new FileReader(file));
-        String line = "";
-        try {
-            line = br.readLine();
-            return Long.parseLong(line);
-        } catch (NumberFormatException e) {
-            throw new IOException("Found " + line + " in " + file);
-        } finally {
-            br.close();
-        }
-    }
-
-    private long acceptedEpoch = -1;
-    private long currentEpoch = -1;
-
-    public static final String CURRENT_EPOCH_FILENAME = "currentEpoch";
-
-    public static final String ACCEPTED_EPOCH_FILENAME = "acceptedEpoch";
-
-    /**
-     * Write a long value to disk atomically. Either succeeds or an exception
-     * is thrown.
-     * @param name file name to write the long to
-     * @param value the long value to write to the named file
-     * @throws IOException if the file cannot be written atomically
-     */
-    // visibleForTest
-     void writeLongToFile(String name, final long value) throws IOException {
-        File file = new File(logFactory.getSnapDir(), name);
-        new AtomicFileWritingIdiom(file, new WriterStatement() {
-            @Override
-            public void write(Writer bw) throws IOException {
-                bw.write(Long.toString(value));
-            }
-        });
-    }
-
-    public long getCurrentEpoch() throws IOException {
-        if (currentEpoch == -1) {
-            currentEpoch = readLongFromFile(CURRENT_EPOCH_FILENAME);
-        }
-        return currentEpoch;
-    }
-
-    public long getAcceptedEpoch() throws IOException {
-        if (acceptedEpoch == -1) {
-            acceptedEpoch = readLongFromFile(ACCEPTED_EPOCH_FILENAME);
-        }
-        return acceptedEpoch;
-    }
-
-    public void setCurrentEpoch(long e) throws IOException {
-        writeLongToFile(CURRENT_EPOCH_FILENAME, e);
-        currentEpoch = e;
-    }
-
-    public void setAcceptedEpoch(long e) throws IOException {
-        writeLongToFile(ACCEPTED_EPOCH_FILENAME, e);
-        acceptedEpoch = e;
-    }
-
-    public boolean processReconfig(QuorumVerifier qv, Long suggestedLeaderId, Long zxid, boolean restartLE) {
-        if (!isReconfigEnabled()) {
-            LOG.debug("Reconfig feature is disabled, skip reconfig processing.");
-            return false;
-        }
-
-        InetSocketAddress oldClientAddr = getClientAddress();
-
-        // update last committed quorum verifier, write the new config to disk
-        // and restart leader election if config changed.
-        QuorumVerifier prevQV = setQuorumVerifier(qv, true);
-
-        // There is no log record for the initial config, thus after syncing
-        // with leader
-        // /zookeeper/config is empty! it is also possible that last committed
-        // config is propagated during leader election
-        // without the propagation the corresponding log records.
-        // so we should explicitly do this (this is not necessary when we're
-        // already a Follower/Observer, only
-        // for Learner):
-        initConfigInZKDatabase();
-
-        if (prevQV.getVersion() < qv.getVersion() && !prevQV.equals(qv)) {
-            Map<Long, QuorumServer> newMembers = qv.getAllMembers();
-            updateRemotePeerMXBeans(newMembers);
-            if (restartLE) {
-                restartLeaderElection(prevQV, qv);
-            }
-
-            QuorumServer myNewQS = newMembers.get(getMyId());
-            if (myNewQS != null && myNewQS.clientAddr != null && !myNewQS.clientAddr.equals(oldClientAddr)) {
-                cnxnFactory.reconfigure(myNewQS.clientAddr);
-                updateThreadName();
-            }
-
-            boolean roleChange = updateLearnerType(qv);
-            boolean leaderChange = false;
-            if (suggestedLeaderId != null) {
-                // zxid should be non-null too
-                leaderChange = updateVote(suggestedLeaderId, zxid);
-            } else {
-                long currentLeaderId = getCurrentVote().getId();
-                QuorumServer myleaderInCurQV = prevQV.getVotingMembers().get(currentLeaderId);
-                QuorumServer myleaderInNewQV = qv.getVotingMembers().get(currentLeaderId);
-                leaderChange = (myleaderInCurQV == null
-                                || myleaderInCurQV.addr == null
-                                || myleaderInNewQV == null
-                                || !myleaderInCurQV.addr.equals(myleaderInNewQV.addr));
-                // we don't have a designated leader - need to go into leader
-                // election
-                reconfigFlagClear();
-            }
-
-            return roleChange || leaderChange;
-        }
-        return false;
-
-    }
-
-    private void updateRemotePeerMXBeans(Map<Long, QuorumServer> newMembers) {
-        Set<Long> existingMembers = new HashSet<>(newMembers.keySet());
-        existingMembers.retainAll(jmxRemotePeerBean.keySet());
-        for (Long id : existingMembers) {
-            RemotePeerBean rBean = jmxRemotePeerBean.get(id);
-            rBean.setQuorumServer(newMembers.get(id));
-        }
-
-        Set<Long> joiningMembers = new HashSet<>(newMembers.keySet());
-        joiningMembers.removeAll(jmxRemotePeerBean.keySet());
-        joiningMembers.remove(getMyId()); // remove self as it is local bean
-        for (Long id : joiningMembers) {
-            QuorumServer qs = newMembers.get(id);
-            RemotePeerBean rBean = new RemotePeerBean(this, qs);
-            try {
-                MBeanRegistry.getInstance().register(rBean, jmxQuorumBean);
-                jmxRemotePeerBean.put(qs.id, rBean);
-            } catch (Exception e) {
-                LOG.warn("Failed to register with JMX", e);
-            }
-        }
-
-        Set<Long> leavingMembers = new HashSet<>(jmxRemotePeerBean.keySet());
-        leavingMembers.removeAll(newMembers.keySet());
-        for (Long id : leavingMembers) {
-            RemotePeerBean rBean = jmxRemotePeerBean.remove(id);
-            try {
-                MBeanRegistry.getInstance().unregister(rBean);
-            } catch (Exception e) {
-                LOG.warn("Failed to unregister with JMX", e);
-            }
-        }
-    }
-
-    private ArrayList<QuorumServer> observerMasters = new ArrayList<>();
-    private void updateObserverMasterList() {
-        if (observerMasterPort <= 0) {
-            return; // observer masters not enabled
-        }
-        observerMasters.clear();
-        StringBuilder sb = new StringBuilder();
-        for (QuorumServer server : quorumVerifier.getVotingMembers().values()) {
-            InetAddress address = server.addr.getReachableOrOne().getAddress();
-            InetSocketAddress addr = new InetSocketAddress(address, observerMasterPort);
-            observerMasters.add(new QuorumServer(server.id, addr));
-            sb.append(addr).append(",");
-        }
-        LOG.info("Updated learner master list to be {}", sb.toString());
-        Collections.shuffle(observerMasters);
-        // Reset the internal index of the observerMaster when
-        // the observerMaster List is refreshed
-        nextObserverMaster = 0;
-    }
-
-    private boolean useObserverMasters() {
-        return getLearnerType() == LearnerType.OBSERVER && observerMasters.size() > 0;
-    }
-
-    private int nextObserverMaster = 0;
-    private QuorumServer nextObserverMaster() {
-        if (nextObserverMaster >= observerMasters.size()) {
-            nextObserverMaster = 0;
-            // Add a reconnect delay only after the observer
-            // has exhausted trying to connect to all the masters
-            // from the observerMasterList
-            if (isRunning()) {
-                Observer.waitForReconnectDelay();
-            }
-        }
-        return observerMasters.get(nextObserverMaster++);
-    }
-
-    QuorumServer findLearnerMaster(QuorumServer leader) {
-        if (useObserverMasters()) {
-            return nextObserverMaster();
-        } else {
-            // Add delay jitter to reduce the load on the leader
-            if (isRunning()) {
-                Observer.waitForReconnectDelay();
-            }
-            return leader;
-        }
-    }
-
-    /**
-     * Vet a given learner master's information.
-     * Allows specification by server id, ip  only, or ip and port
-     */
-    QuorumServer validateLearnerMaster(String desiredMaster) {
-        if (useObserverMasters()) {
-            Long sid;
-            try {
-                sid = Long.parseLong(desiredMaster);
-            } catch (NumberFormatException e) {
-                sid = null;
-            }
-            for (QuorumServer server : observerMasters) {
-                if (sid == null) {
-                    for (InetSocketAddress address : server.addr.getAllAddresses()) {
-                        String serverAddr = address.getAddress().getHostAddress() + ':' + address.getPort();
-                        if (serverAddr.startsWith(desiredMaster)) {
-                            return server;
-                        }
-                    }
-                } else {
-                    if (sid.equals(server.id)) {
-                        return server;
-                    }
-                }
-            }
-            if (sid == null) {
-                LOG.info("could not find learner master address={}", desiredMaster);
-            } else {
-                LOG.warn("could not find learner master sid={}", sid);
-            }
-        } else {
-            LOG.info("cannot validate request, observer masters not enabled");
-        }
-        return null;
-    }
-
-    private boolean updateLearnerType(QuorumVerifier newQV) {
-        //check if I'm an observer in new config
-        if (newQV.getObservingMembers().containsKey(getMyId())) {
-            if (getLearnerType() != LearnerType.OBSERVER) {
-                setLearnerType(LearnerType.OBSERVER);
-                LOG.info("Becoming an observer");
-                reconfigFlagSet();
-                return true;
-            } else {
-                return false;
-            }
-        } else if (newQV.getVotingMembers().containsKey(getMyId())) {
-            if (getLearnerType() != LearnerType.PARTICIPANT) {
-                setLearnerType(LearnerType.PARTICIPANT);
-                LOG.info("Becoming a voting participant");
-                reconfigFlagSet();
-                return true;
-            } else {
-                return false;
-            }
-        }
-        // I'm not in the view
-        if (getLearnerType() != LearnerType.PARTICIPANT) {
-            setLearnerType(LearnerType.PARTICIPANT);
-            LOG.info("Becoming a non-voting participant");
-            reconfigFlagSet();
-            return true;
-        }
-        return false;
-    }
-
-    private boolean updateVote(long designatedLeader, long zxid) {
-        Vote currentVote = getCurrentVote();
-        if (currentVote != null && designatedLeader != currentVote.getId()) {
-            setCurrentVote(new Vote(designatedLeader, zxid));
-            reconfigFlagSet();
-            LOG.warn("Suggested leader: {}", designatedLeader);
-            return true;
-        }
-        return false;
-    }
-
-    /**
-     * Updates leader election info to avoid inconsistencies when
-     * a new server tries to join the ensemble.
-     *
-     * Here is the inconsistency scenario we try to solve by updating the peer
-     * epoch after following leader:
-     *
-     * Let's say we have an ensemble with 3 servers z1, z2 and z3.
-     *
-     * 1. z1, z2 were following z3 with peerEpoch to be 0xb8, the new epoch is
-     *    0xb9, aka current accepted epoch on disk.
-     * 2. z2 get restarted, which will use 0xb9 as it's peer epoch when loading
-     *    the current accept epoch from disk.
-     * 3. z2 received notification from z1 and z3, which is following z3 with
-     *    epoch 0xb8, so it started following z3 again with peer epoch 0xb8.
-     * 4. before z2 successfully connected to z3, z3 get restarted with new
-     *    epoch 0xb9.
-     * 5. z2 will retry around a few round (default 5s) before giving up,
-     *    meanwhile it will report z3 as leader.
-     * 6. z1 restarted, and looking with peer epoch 0xb9.
-     * 7. z1 voted z3, and z3 was elected as leader again with peer epoch 0xb9.
-     * 8. z2 successfully connected to z3 before giving up, but with peer
-     *    epoch 0xb8.
-     * 9. z1 get restarted, looking for leader with peer epoch 0xba, but cannot
-     *    join, because z2 is reporting peer epoch 0xb8, while z3 is reporting
-     *    0xb9.
-     *
-     * By updating the election vote after actually following leader, we can
-     * avoid this kind of stuck happened.
-     *
-     * Btw, the zxid and electionEpoch could be inconsistent because of the same
-     * reason, it's better to update these as well after syncing with leader, but
-     * that required protocol change which is non trivial. This problem is worked
-     * around by skipping comparing the zxid and electionEpoch when counting for
-     * votes for out of election servers during looking for leader.
-     *
-     * See https://issues.apache.org/jira/browse/ZOOKEEPER-1732
-     */
-    protected void updateElectionVote(long newEpoch) {
-        Vote currentVote = getCurrentVote();
-        if (currentVote != null) {
-            setCurrentVote(new Vote(currentVote.getId(), currentVote.getZxid(), currentVote.getElectionEpoch(), newEpoch, currentVote
-                .getState()));
-        }
-    }
-
-    private void updateThreadName() {
-        String plain = cnxnFactory != null
-                ? cnxnFactory.getLocalAddress() != null
-                    ? formatInetAddr(cnxnFactory.getLocalAddress())
-                    : "disabled"
-                : "disabled";
-        String secure = secureCnxnFactory != null ? formatInetAddr(secureCnxnFactory.getLocalAddress()) : "disabled";
-        setName(String.format("QuorumPeer[myid=%d](plain=%s)(secure=%s)", getMyId(), plain, secure));
-    }
-
-    /**
-     * Sets the time taken for leader election in milliseconds.
-     *
-     * @param electionTimeTaken time taken for leader election
-     */
-    void setElectionTimeTaken(long electionTimeTaken) {
-        this.electionTimeTaken = electionTimeTaken;
-    }
-
-    /**
-     * @return the time taken for leader election in milliseconds.
-     */
-    long getElectionTimeTaken() {
-        return electionTimeTaken;
-    }
-
-    void setQuorumServerSaslRequired(boolean serverSaslRequired) {
-        quorumServerSaslAuthRequired = serverSaslRequired;
-        LOG.info("{} set to {}", QuorumAuth.QUORUM_SERVER_SASL_AUTH_REQUIRED, serverSaslRequired);
-    }
-
-    void setQuorumLearnerSaslRequired(boolean learnerSaslRequired) {
-        quorumLearnerSaslAuthRequired = learnerSaslRequired;
-        LOG.info("{} set to {}", QuorumAuth.QUORUM_LEARNER_SASL_AUTH_REQUIRED, learnerSaslRequired);
-    }
-
-    void setQuorumSaslEnabled(boolean enableAuth) {
-        quorumSaslEnableAuth = enableAuth;
-        if (!quorumSaslEnableAuth) {
-            LOG.info("QuorumPeer communication is not secured! (SASL auth disabled)");
-        } else {
-            LOG.info("{} set to {}", QuorumAuth.QUORUM_SASL_AUTH_ENABLED, enableAuth);
-        }
-    }
-
-    void setQuorumServicePrincipal(String servicePrincipal) {
-        quorumServicePrincipal = servicePrincipal;
-        LOG.info("{} set to {}", QuorumAuth.QUORUM_KERBEROS_SERVICE_PRINCIPAL, quorumServicePrincipal);
-    }
-
-    void setQuorumLearnerLoginContext(String learnerContext) {
-        quorumLearnerLoginContext = learnerContext;
-        LOG.info("{} set to {}", QuorumAuth.QUORUM_LEARNER_SASL_LOGIN_CONTEXT, quorumLearnerLoginContext);
-    }
-
-    void setQuorumServerLoginContext(String serverContext) {
-        quorumServerLoginContext = serverContext;
-        LOG.info("{} set to {}", QuorumAuth.QUORUM_SERVER_SASL_LOGIN_CONTEXT, quorumServerLoginContext);
-    }
-
-    void setQuorumCnxnThreadsSize(int qCnxnThreadsSize) {
-        if (qCnxnThreadsSize > QUORUM_CNXN_THREADS_SIZE_DEFAULT_VALUE) {
-            quorumCnxnThreadsSize = qCnxnThreadsSize;
-        }
-        LOG.info("quorum.cnxn.threads.size set to {}", quorumCnxnThreadsSize);
-    }
-
-    boolean isQuorumSaslAuthEnabled() {
-        return quorumSaslEnableAuth;
-    }
-
-    private boolean isQuorumServerSaslAuthRequired() {
-        return quorumServerSaslAuthRequired;
-    }
-
-    private boolean isQuorumLearnerSaslAuthRequired() {
-        return quorumLearnerSaslAuthRequired;
-    }
-
-    public QuorumCnxManager createCnxnManager() {
-        int timeout = quorumCnxnTimeoutMs > 0 ? quorumCnxnTimeoutMs : this.tickTime * this.syncLimit;
-        LOG.info("Using {}ms as the quorum cnxn socket timeout", timeout);
-        return new QuorumCnxManager(
-            this,
-            this.getMyId(),
-            this.getView(),
-            this.authServer,
-            this.authLearner,
-            timeout,
-            this.getQuorumListenOnAllIPs(),
-            this.quorumCnxnThreadsSize,
-            this.isQuorumSaslAuthEnabled());
-    }
-
-    boolean isLeader(long id) {
-        Vote vote = getCurrentVote();
-        return vote != null && id == vote.getId();
-    }
-
-    public boolean isReconfigEnabled() {
-        return reconfigEnabled;
-    }
-
-    @InterfaceAudience.Private
-    /**
-     * This is a metric that depends on the status of the peer.
-     */ public Integer getSynced_observers_metric() {
-        if (leader != null) {
-            return leader.getObservingLearners().size();
-        } else if (follower != null) {
-            return follower.getSyncedObserverSize();
-        } else {
-            return null;
-        }
-    }
-
-    /**
-     * Create a new QuorumPeer and apply all the values per the already-parsed config.
-     *
-     * @param config The appertained quorum peer config.
-     * @return A QuorumPeer instantiated with specified peer config. Note this peer
-     *         is not fully initialized; caller should finish initialization through
-     *         additional configurations (connection factory settings, etc).
-     *
-     * @throws IOException
-     */
-    public static QuorumPeer createFromConfig(QuorumPeerConfig config) throws IOException {
-        QuorumPeer quorumPeer = new QuorumPeer();
-        quorumPeer.setTxnFactory(new FileTxnSnapLog(config.getDataLogDir(), config.getDataDir()));
-        quorumPeer.enableLocalSessions(config.areLocalSessionsEnabled());
-        quorumPeer.enableLocalSessionsUpgrading(config.isLocalSessionsUpgradingEnabled());
-        quorumPeer.setElectionType(config.getElectionAlg());
-        quorumPeer.setMyid(config.getServerId());
-        quorumPeer.setTickTime(config.getTickTime());
-        quorumPeer.setMinSessionTimeout(config.getMinSessionTimeout());
-        quorumPeer.setMaxSessionTimeout(config.getMaxSessionTimeout());
-        quorumPeer.setInitLimit(config.getInitLimit());
-        quorumPeer.setSyncLimit(config.getSyncLimit());
-        quorumPeer.setConnectToLearnerMasterLimit(config.getConnectToLearnerMasterLimit());
-        quorumPeer.setObserverMasterPort(config.getObserverMasterPort());
-        quorumPeer.setConfigFileName(config.getConfigFilename());
-        quorumPeer.setClientPortListenBacklog(config.getClientPortListenBacklog());
-        quorumPeer.setZKDatabase(new ZKDatabase(quorumPeer.getTxnFactory()));
-        quorumPeer.setQuorumVerifier(config.getQuorumVerifier(), false);
-        if (config.getLastSeenQuorumVerifier() != null) {
-            quorumPeer.setLastSeenQuorumVerifier(config.getLastSeenQuorumVerifier(), false);
-        }
-        quorumPeer.initConfigInZKDatabase();
-        quorumPeer.setSslQuorum(config.isSslQuorum());
-        quorumPeer.setUsePortUnification(config.shouldUsePortUnification());
-        quorumPeer.setLearnerType(config.getPeerType());
-        quorumPeer.setSyncEnabled(config.getSyncEnabled());
-        quorumPeer.setQuorumListenOnAllIPs(config.getQuorumListenOnAllIPs());
-        if (config.sslQuorumReloadCertFiles) {
-            quorumPeer.getX509Util().enableCertFileReloading();
-        }
-        quorumPeer.setMultiAddressEnabled(config.isMultiAddressEnabled());
-        quorumPeer.setMultiAddressReachabilityCheckEnabled(config.isMultiAddressReachabilityCheckEnabled());
-        quorumPeer.setMultiAddressReachabilityCheckTimeoutMs(config.getMultiAddressReachabilityCheckTimeoutMs());
-
-        // sets quorum sasl authentication configurations
-        quorumPeer.setQuorumSaslEnabled(config.quorumEnableSasl);
-        if (quorumPeer.isQuorumSaslAuthEnabled()) {
-            quorumPeer.setQuorumServerSaslRequired(config.quorumServerRequireSasl);
-            quorumPeer.setQuorumLearnerSaslRequired(config.quorumLearnerRequireSasl);
-            quorumPeer.setQuorumServicePrincipal(config.quorumServicePrincipal);
-            quorumPeer.setQuorumServerLoginContext(config.quorumServerLoginContext);
-            quorumPeer.setQuorumLearnerLoginContext(config.quorumLearnerLoginContext);
-        }
-        quorumPeer.setQuorumCnxnThreadsSize(config.quorumCnxnThreadsSize);
-
-        if (config.jvmPauseMonitorToRun) {
-            quorumPeer.setJvmPauseMonitor(new JvmPauseMonitor(config));
-        }
-
-        return quorumPeer;
-    }
-
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/ReadOnlyZooKeeperServer.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/ReadOnlyZooKeeperServer.java
deleted file mode 100644
index a96a395b03b..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/ReadOnlyZooKeeperServer.java
+++ /dev/null
@@ -1,236 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.zookeeper.server.quorum;
-
-import java.io.IOException;
-import java.io.PrintWriter;
-import java.util.Objects;
-import java.util.stream.Collectors;
-import org.apache.zookeeper.ZooDefs.OpCode;
-import org.apache.zookeeper.jmx.MBeanRegistry;
-import org.apache.zookeeper.server.DataTreeBean;
-import org.apache.zookeeper.server.FinalRequestProcessor;
-import org.apache.zookeeper.server.PrepRequestProcessor;
-import org.apache.zookeeper.server.Request;
-import org.apache.zookeeper.server.RequestProcessor;
-import org.apache.zookeeper.server.ServerCnxn;
-import org.apache.zookeeper.server.ZKDatabase;
-import org.apache.zookeeper.server.ZooKeeperServer;
-import org.apache.zookeeper.server.ZooKeeperServerBean;
-import org.apache.zookeeper.server.persistence.FileTxnSnapLog;
-
-/**
- * A ZooKeeperServer which comes into play when peer is partitioned from the
- * majority. Handles read-only clients, but drops connections from not-read-only
- * ones.
- * <p>
- * The very first processor in the chain of request processors is a
- * ReadOnlyRequestProcessor which drops state-changing requests.
- */
-public class ReadOnlyZooKeeperServer extends ZooKeeperServer {
-
-    protected final QuorumPeer self;
-    private volatile boolean shutdown = false;
-
-    ReadOnlyZooKeeperServer(FileTxnSnapLog logFactory, QuorumPeer self, ZKDatabase zkDb) {
-        super(
-            logFactory,
-            self.tickTime,
-            self.minSessionTimeout,
-            self.maxSessionTimeout,
-            self.clientPortListenBacklog,
-            zkDb,
-            self.getInitialConfig(),
-            self.isReconfigEnabled());
-        this.self = self;
-    }
-
-    @Override
-    protected void setupRequestProcessors() {
-        RequestProcessor finalProcessor = new FinalRequestProcessor(this);
-        RequestProcessor prepProcessor = new PrepRequestProcessor(this, finalProcessor);
-        ((PrepRequestProcessor) prepProcessor).start();
-        firstProcessor = new ReadOnlyRequestProcessor(this, prepProcessor);
-        ((ReadOnlyRequestProcessor) firstProcessor).start();
-    }
-
-    @Override
-    public synchronized void startup() {
-        // check to avoid startup follows shutdown
-        if (shutdown) {
-            LOG.warn("Not starting Read-only server as startup follows shutdown!");
-            return;
-        }
-        registerJMX(new ReadOnlyBean(this), self.jmxLocalPeerBean);
-        super.startup();
-        self.setZooKeeperServer(this);
-        self.adminServer.setZooKeeperServer(this);
-        LOG.info("Read-only server started");
-    }
-
-    @Override
-    public void createSessionTracker() {
-        sessionTracker = new LearnerSessionTracker(
-                this, getZKDatabase().getSessionWithTimeOuts(),
-                this.tickTime, self.getMyId(), self.areLocalSessionsEnabled(),
-                getZooKeeperServerListener());
-    }
-
-    @Override
-    protected void startSessionTracker() {
-        ((LearnerSessionTracker) sessionTracker).start();
-    }
-
-    @Override
-    protected void setLocalSessionFlag(Request si) {
-        switch (si.type) {
-            case OpCode.createSession:
-                if (self.areLocalSessionsEnabled()) {
-                    si.setLocalSession(true);
-                }
-                break;
-            case OpCode.closeSession:
-                if (((UpgradeableSessionTracker) sessionTracker).isLocalSession(si.sessionId)) {
-                    si.setLocalSession(true);
-                } else {
-                    LOG.warn("Submitting global closeSession request for session 0x{} in ReadOnly mode",
-                            Long.toHexString(si.sessionId));
-                }
-                break;
-            default:
-                break;
-        }
-    }
-
-    @Override
-    protected void validateSession(ServerCnxn cnxn, long sessionId) throws IOException {
-        if (((LearnerSessionTracker) sessionTracker).isGlobalSession(sessionId)) {
-            String msg = "Refusing global session reconnection in RO mode " + cnxn.getRemoteSocketAddress();
-            LOG.info(msg);
-            throw new ServerCnxn.CloseRequestException(msg, ServerCnxn.DisconnectReason.RENEW_GLOBAL_SESSION_IN_RO_MODE);
-        }
-    }
-
-    @Override
-    protected void registerJMX() {
-        // register with JMX
-        try {
-            jmxDataTreeBean = new DataTreeBean(getZKDatabase().getDataTree());
-            MBeanRegistry.getInstance().register(jmxDataTreeBean, jmxServerBean);
-        } catch (Exception e) {
-            LOG.warn("Failed to register with JMX", e);
-            jmxDataTreeBean = null;
-        }
-    }
-
-    public void registerJMX(ZooKeeperServerBean serverBean, LocalPeerBean localPeerBean) {
-        // register with JMX
-        try {
-            jmxServerBean = serverBean;
-            MBeanRegistry.getInstance().register(serverBean, localPeerBean);
-        } catch (Exception e) {
-            LOG.warn("Failed to register with JMX", e);
-            jmxServerBean = null;
-        }
-    }
-
-    @Override
-    protected void unregisterJMX() {
-        // unregister from JMX
-        try {
-            if (jmxDataTreeBean != null) {
-                MBeanRegistry.getInstance().unregister(jmxDataTreeBean);
-            }
-        } catch (Exception e) {
-            LOG.warn("Failed to unregister with JMX", e);
-        }
-        jmxDataTreeBean = null;
-    }
-
-    protected void unregisterJMX(ZooKeeperServer zks) {
-        // unregister from JMX
-        try {
-            if (jmxServerBean != null) {
-                MBeanRegistry.getInstance().unregister(jmxServerBean);
-            }
-        } catch (Exception e) {
-            LOG.warn("Failed to unregister with JMX", e);
-        }
-        jmxServerBean = null;
-    }
-
-    @Override
-    public String getState() {
-        return "read-only";
-    }
-
-    /**
-     * Returns the id of the associated QuorumPeer, which will do for a unique
-     * id of this server.
-     */
-    @Override
-    public long getServerId() {
-        return self.getMyId();
-    }
-
-    @Override
-    public synchronized void shutdown(boolean fullyShutDown) {
-        if (!canShutdown()) {
-            LOG.debug("ZooKeeper server is not running, so not proceeding to shutdown!");
-        } else {
-            shutdown = true;
-            unregisterJMX(this);
-
-            // set peer's server to null
-            self.setZooKeeperServer(null);
-            // clear all the connections
-            self.closeAllConnections();
-
-            self.adminServer.setZooKeeperServer(null);
-        }
-        // shutdown the server itself
-        super.shutdown(fullyShutDown);
-    }
-
-    @Override
-    public void dumpConf(PrintWriter pwriter) {
-        super.dumpConf(pwriter);
-
-        pwriter.print("initLimit=");
-        pwriter.println(self.getInitLimit());
-        pwriter.print("syncLimit=");
-        pwriter.println(self.getSyncLimit());
-        pwriter.print("electionAlg=");
-        pwriter.println(self.getElectionType());
-        pwriter.print("electionPort=");
-        pwriter.println(self.getElectionAddress().getAllPorts()
-                .stream().map(Objects::toString).collect(Collectors.joining("|")));
-        pwriter.print("quorumPort=");
-        pwriter.println(self.getQuorumAddress().getAllPorts()
-                .stream().map(Objects::toString).collect(Collectors.joining("|")));
-        pwriter.print("peerType=");
-        pwriter.println(self.getLearnerType().ordinal());
-    }
-
-    @Override
-    protected void setState(State state) {
-        this.state = state;
-    }
-
-}
diff --git a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/SendAckRequestProcessor.java b/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/SendAckRequestProcessor.java
deleted file mode 100644
index d65ead216f0..00000000000
--- a/zookeeper-server/zookeeper-server-3.9.2/src/main/java/org/apache/zookeeper/server/quorum/SendAckRequestProcessor.java
+++ /dev/null
@@ -1,83 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.apache.zookeeper.server.quorum;
-
-import java.io.Flushable;
-import java.io.IOException;
-import java.net.Socket;
-import org.apache.zookeeper.ZooDefs.OpCode;
-import org.apache.zookeeper.server.Request;
-import org.apache.zookeeper.server.RequestProcessor;
-import org.apache.zookeeper.server.ServerMetrics;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-public class SendAckRequestProcessor implements RequestProcessor, Flushable {
-
-    private static final Logger LOG = LoggerFactory.getLogger(SendAckRequestProcessor.class);
-
-    final Learner learner;
-
-    SendAckRequestProcessor(Learner peer) {
-        this.learner = peer;
-    }
-
-    public void processRequest(Request si) {
-        if (si.type != OpCode.sync) {
-            QuorumPacket qp = new QuorumPacket(Leader.ACK, si.getHdr().getZxid(), null, null);
-            try {
-                si.logLatency(ServerMetrics.getMetrics().PROPOSAL_ACK_CREATION_LATENCY);
-
-                learner.writePacket(qp, false);
-            } catch (IOException e) {
-                LOG.warn("Closing connection to leader, exception during packet send", e);
-                try {
-                    if (!learner.sock.isClosed()) {
-                        learner.sock.close();
-                    }
-                } catch (IOException e1) {
-                    // Nothing to do, we are shutting things down, so an exception here is irrelevant
-                    LOG.debug("Ignoring error closing the connection", e1);
-                }
-            }
-        }
-    }
-
-    public void flush() throws IOException {
-        try {
-            learner.writePacket(null, true);
-        } catch (IOException e) {
-            LOG.warn("Closing connection to leader, exception during packet send", e);
-            try {
-                Socket socket = learner.sock;
-                if (socket != null && !socket.isClosed()) {
-                    learner.sock.close();
-                }
-            } catch (IOException e1) {
-                // Nothing to do, we are shutting things down, so an exception here is irrelevant
-                LOG.debug("Ignoring error closing the connection", e1);
-            }
-        }
-    }
-
-    public void shutdown() {
-        // Nothing needed
-    }
-
-}
diff --git a/zookeeper-server/zookeeper-server/CMakeLists.txt b/zookeeper-server/zookeeper-server/CMakeLists.txt
index c7e9679ed24..30ed1ed4404 100644
--- a/zookeeper-server/zookeeper-server/CMakeLists.txt
+++ b/zookeeper-server/zookeeper-server/CMakeLists.txt
@@ -1,4 +1,4 @@
 # Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-install_jar(zookeeper-server-3.9.1-jar-with-dependencies.jar)
+install_jar(zookeeper-server-3.9.2-jar-with-dependencies.jar)
 # Make symlink so that we have a default version, should be done only in zookeeper-server module
-install_symlink(lib/jars/zookeeper-server-3.9.1-jar-with-dependencies.jar lib/jars/zookeeper-server-jar-with-dependencies.jar)
+install_symlink(lib/jars/zookeeper-server-3.9.2-jar-with-dependencies.jar lib/jars/zookeeper-server-jar-with-dependencies.jar)
diff --git a/zookeeper-server/zookeeper-server/pom.xml b/zookeeper-server/zookeeper-server/pom.xml
index f1b33dd0ae7..791c026234a 100644
--- a/zookeeper-server/zookeeper-server/pom.xml
+++ b/zookeeper-server/zookeeper-server/pom.xml
@@ -8,11 +8,11 @@
     <version>8-SNAPSHOT</version>
     <relativePath>../pom.xml</relativePath>
   </parent>
-  <artifactId>zookeeper-server-3.9.1</artifactId>
+  <artifactId>zookeeper-server-3.9.2</artifactId>
   <packaging>container-plugin</packaging>
   <version>8-SNAPSHOT</version>
   <properties>
-    <zookeeper.version>3.9.1</zookeeper.version>
+    <zookeeper.version>3.9.2</zookeeper.version>
   </properties>
   <dependencies>
     <dependency>
diff --git a/zookeeper-server/zookeeper-server/src/main/java/com/yahoo/vespa/zookeeper/VespaZooKeeperAdminImpl.java b/zookeeper-server/zookeeper-server/src/main/java/com/yahoo/vespa/zookeeper/VespaZooKeeperAdminImpl.java
index 891a35582b3..c74a020bcf4 100644
--- a/zookeeper-server/zookeeper-server/src/main/java/com/yahoo/vespa/zookeeper/VespaZooKeeperAdminImpl.java
+++ b/zookeeper-server/zookeeper-server/src/main/java/com/yahoo/vespa/zookeeper/VespaZooKeeperAdminImpl.java
@@ -26,6 +26,7 @@ public class VespaZooKeeperAdminImpl implements VespaZooKeeperAdmin {
 
     private static final Logger log = java.util.logging.Logger.getLogger(VespaZooKeeperAdminImpl.class.getName());
 
+
     @SuppressWarnings("try")
     @Override
     public void reconfigure(String connectionSpec, String servers) throws ReconfigException {
diff --git a/zookeeper-server/zookeeper-server/src/main/java/org/apache/zookeeper/server/ZooKeeperServer.java b/zookeeper-server/zookeeper-server/src/main/java/org/apache/zookeeper/server/ZooKeeperServer.java
index 895bbeffa5f..00af31b46d4 100644
--- a/zookeeper-server/zookeeper-server/src/main/java/org/apache/zookeeper/server/ZooKeeperServer.java
+++ b/zookeeper-server/zookeeper-server/src/main/java/org/apache/zookeeper/server/ZooKeeperServer.java
@@ -384,13 +384,13 @@ public class ZooKeeperServer implements SessionExpirer, ServerStats.Provider {
                 + " minSessionTimeout {} ms"
                 + " maxSessionTimeout {} ms"
                 + " clientPortListenBacklog {}"
-                + " datadir {}"
+                + " dataLogdir {}"
                 + " snapdir {}",
             tickTime,
             getMinSessionTimeout(),
             getMaxSessionTimeout(),
             getClientPortListenBacklog(),
-            txnLogFactory.getDataDir(),
+            txnLogFactory.getDataLogDir(),
             txnLogFactory.getSnapDir());
     }
 
@@ -442,7 +442,7 @@ public class ZooKeeperServer implements SessionExpirer, ServerStats.Provider {
         pwriter.print("dataDirSize=");
         pwriter.println(getDataDirSize());
         pwriter.print("dataLogDir=");
-        pwriter.println(zkDb.snapLog.getDataDir().getAbsolutePath());
+        pwriter.println(zkDb.snapLog.getDataLogDir().getAbsolutePath());
         pwriter.print("dataLogSize=");
         pwriter.println(getLogDirSize());
         pwriter.print("tickTime=");
@@ -464,7 +464,7 @@ public class ZooKeeperServer implements SessionExpirer, ServerStats.Provider {
         return new ZooKeeperServerConf(
             getClientPort(),
             zkDb.snapLog.getSnapDir().getAbsolutePath(),
-            zkDb.snapLog.getDataDir().getAbsolutePath(),
+            zkDb.snapLog.getDataLogDir().getAbsolutePath(),
             getTickTime(),
             getMaxClientCnxnsPerHost(),
             getMinSessionTimeout(),
@@ -649,7 +649,7 @@ public class ZooKeeperServer implements SessionExpirer, ServerStats.Provider {
         if (zkDb == null) {
             return 0L;
         }
-        File path = zkDb.snapLog.getDataDir();
+        File path = zkDb.snapLog.getSnapDir();
         return getDirSize(path);
     }
 
@@ -658,7 +658,7 @@ public class ZooKeeperServer implements SessionExpirer, ServerStats.Provider {
         if (zkDb == null) {
             return 0L;
         }
-        File path = zkDb.snapLog.getSnapDir();
+        File path = zkDb.snapLog.getDataLogDir();
         return getDirSize(path);
     }
 
@@ -1506,7 +1506,9 @@ public class ZooKeeperServer implements SessionExpirer, ServerStats.Provider {
             throw new CloseRequestException(msg, ServerCnxn.DisconnectReason.NOT_READ_ONLY_CLIENT);
         }
         if (request.getLastZxidSeen() > zkDb.dataTree.lastProcessedZxid) {
-            String msg = "Refusing session request for client "
+            String msg = "Refusing session(0x"
+                         + Long.toHexString(sessionId)
+                         + ") request for client "
                          + cnxn.getRemoteSocketAddress()
                          + " as it has seen zxid 0x"
                          + Long.toHexString(request.getLastZxidSeen())
diff --git a/zookeeper-server/zookeeper-server/src/main/java/org/apache/zookeeper/server/quorum/Learner.java b/zookeeper-server/zookeeper-server/src/main/java/org/apache/zookeeper/server/quorum/Learner.java
index 8d8b6dabce8..3c7b2148400 100644
--- a/zookeeper-server/zookeeper-server/src/main/java/org/apache/zookeeper/server/quorum/Learner.java
+++ b/zookeeper-server/zookeeper-server/src/main/java/org/apache/zookeeper/server/quorum/Learner.java
@@ -597,7 +597,6 @@ public class Learner {
                     willSnapshot = false;          // but anything after this needs to go to the transaction log; or
                 }
 
-                self.setCurrentEpoch(newEpoch);
                 sock.setSoTimeout(self.tickTime * self.syncLimit);
                 self.setSyncMode(QuorumPeer.SyncMode.NONE);
                 zk.startupWithoutServing();
@@ -613,6 +612,8 @@ public class Learner {
                     delayedProposals.clear();
                     fzk.syncProcessor.syncFlush();
                 }
+
+                self.setCurrentEpoch(newEpoch);
             }
 
             void flushAcks() throws InterruptedException {