Support reconfiguration without config

3 files changed, 75 insertions, 4 deletions

diff --git a/zookeeper-server/zookeeper-server-common/src/main/java/com/yahoo/vespa/zookeeper/Reconfigurer.java b/zookeeper-server/zookeeper-server-common/src/main/java/com/yahoo/vespa/zookeeper/Reconfigurer.java
index 9c2a543d2ef..ba2e8d9c92b 100644
--- a/zookeeper-server/zookeeper-server-common/src/main/java/com/yahoo/vespa/zookeeper/Reconfigurer.java
+++ b/zookeeper-server/zookeeper-server-common/src/main/java/com/yahoo/vespa/zookeeper/Reconfigurer.java
@@ -20,7 +20,7 @@ import java.util.logging.Logger;
 import java.util.stream.Collectors;
 
 /**
- * Starts zookeeper server and supports reconfiguring zookeeper cluster. Created as a component
+ * Starts or reconfigures a ZooKeeper server as necessary. This is created as a component
  * without any config injected, to make sure that it is not recreated when config changes.
  *
  * @author hmusum
@@ -45,12 +45,13 @@ public class Reconfigurer extends AbstractComponent {
         this(vespaZooKeeperAdmin, new Sleeper());
     }
 
-    Reconfigurer(VespaZooKeeperAdmin vespaZooKeeperAdmin, Sleeper sleeper) {
+    public Reconfigurer(VespaZooKeeperAdmin vespaZooKeeperAdmin, Sleeper sleeper) {
         this.vespaZooKeeperAdmin = Objects.requireNonNull(vespaZooKeeperAdmin);
         this.sleeper = Objects.requireNonNull(sleeper);
         log.log(Level.FINE, "Created ZooKeeperReconfigurer");
     }
 
+    /** Start a ZooKeeper server or reconfigure a currently running cluster */
     void startOrReconfigure(ZookeeperServerConfig newConfig, VespaZooKeeperServer server,
                             Supplier<QuorumPeer> quorumPeerGetter, Consumer<QuorumPeer> quorumPeerSetter) {
         if (zooKeeperRunner == null) {
@@ -58,10 +59,22 @@ public class Reconfigurer extends AbstractComponent {
             zooKeeperRunner = startServer(newConfig, server);
         }
         quorumPeerSetter.accept(peer);
+        reconfigure(newConfig);
+    }
 
-        if (shouldReconfigure(newConfig)) {
-            reconfigure(newConfig);
+    /** Reconfigure a running ZooKeeper cluster with given servers. This is a no-op if servers are unchanged */
+    public void reconfigure(List<ZooKeeperServer> wantedServers) {
+        ZookeeperServerConfig.Builder b = new ZookeeperServerConfig.Builder();
+        b.myid(-1) // Required by ZookeeperServerConfig, but not used for reconfiguration
+         .dynamicReconfiguration(true);
+        for (var server : wantedServers) {
+            ZookeeperServerConfig.Server.Builder serverBuilder = new ZookeeperServerConfig.Server.Builder();
+            serverBuilder.id(server.id())
+                         .hostname(server.hostname());
+            b.server(serverBuilder);
         }
+        ZookeeperServerConfig newConfig = b.build();
+        reconfigure(newConfig);
     }
 
     ZookeeperServerConfig activeConfig() {
@@ -86,7 +99,9 @@ public class Reconfigurer extends AbstractComponent {
         return runner;
     }
 
+    /** Reconfigure ZooKeeper cluster with given config, if necessary */
     private void reconfigure(ZookeeperServerConfig newConfig) {
+        if (!shouldReconfigure(newConfig)) return;
         Instant reconfigTriggered = Instant.now();
         // No point in trying to reconfigure if there is only one server in the new ensemble,
         // the others will be shutdown or are about to be shutdown
diff --git a/zookeeper-server/zookeeper-server-common/src/main/java/com/yahoo/vespa/zookeeper/ZooKeeperServer.java b/zookeeper-server/zookeeper-server-common/src/main/java/com/yahoo/vespa/zookeeper/ZooKeeperServer.java
new file mode 100644
index 00000000000..ef75d0b5da7
--- /dev/null
+++ b/zookeeper-server/zookeeper-server-common/src/main/java/com/yahoo/vespa/zookeeper/ZooKeeperServer.java
@@ -0,0 +1,47 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.vespa.zookeeper;
+
+import java.util.Objects;
+
+/**
+ * A ZooKeeper server and its ID.
+ *
+ * @author mpolden
+ */
+public class ZooKeeperServer {
+
+    private final int id;
+    private final String hostname;
+
+    public ZooKeeperServer(int id, String hostname) {
+        if (id < 0 || id > 255) throw new IllegalArgumentException("server id must be between 0 and 255");
+        this.id = id;
+        this.hostname = Objects.requireNonNull(hostname);
+    }
+
+    public int id() {
+        return id;
+    }
+
+    public String hostname() {
+        return hostname;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        ZooKeeperServer that = (ZooKeeperServer) o;
+        return id == that.id && hostname.equals(that.hostname);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(id, hostname);
+    }
+
+    @Override
+    public String toString() {
+        return "server " + id + "=" + hostname;
+    }
+}
diff --git a/zookeeper-server/zookeeper-server-common/src/test/java/com/yahoo/vespa/zookeeper/ReconfigurerTest.java b/zookeeper-server/zookeeper-server-common/src/test/java/com/yahoo/vespa/zookeeper/ReconfigurerTest.java
index 94ccbc26f03..5b99ef70f57 100644
--- a/zookeeper-server/zookeeper-server-common/src/test/java/com/yahoo/vespa/zookeeper/ReconfigurerTest.java
+++ b/zookeeper-server/zookeeper-server-common/src/test/java/com/yahoo/vespa/zookeeper/ReconfigurerTest.java
@@ -14,6 +14,7 @@ import java.io.IOException;
 import java.nio.file.Path;
 import java.time.Duration;
 import java.util.Arrays;
+import java.util.List;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -81,6 +82,14 @@ public class ReconfigurerTest {
         assertEquals("1=node2:2182:2183;2181,2=node3:2182:2183;2181", reconfigurer.joiningServers());
         assertEquals("1,2", reconfigurer.leavingServers());
         assertSame(nextConfig, reconfigurer.activeConfig());
+
+        // Reconfigure without using config
+        reconfigurer.reconfigure(List.of(new ZooKeeperServer(0, "node0"),
+                                         new ZooKeeperServer(1, "node2"),
+                                         new ZooKeeperServer(3, "node4")));
+        assertEquals(4, reconfigurer.reconfigurations());
+        assertEquals("3=node4:2182:2183;2181", reconfigurer.joiningServers());
+        assertEquals("2", reconfigurer.leavingServers());
     }
 
     @Test