Merge pull request #9549 from vespa-engine/jvenstad/zk-watcher-serialisation

Jvenstad/zk watcher serialisation

23 files changed, 226 insertions, 145 deletions

diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/GlobalComponentRegistry.java b/configserver/src/main/java/com/yahoo/vespa/config/server/GlobalComponentRegistry.java
index 2f53973f5af..d420c3f21fe 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/GlobalComponentRegistry.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/GlobalComponentRegistry.java
@@ -2,8 +2,10 @@
 package com.yahoo.vespa.config.server;
 
 import com.yahoo.cloud.config.ConfigserverConfig;
+import com.yahoo.concurrent.StripedExecutor;
 import com.yahoo.config.model.api.ConfigDefinitionRepo;
 import com.yahoo.config.provision.Provisioner;
+import com.yahoo.config.provision.TenantName;
 import com.yahoo.config.provision.Zone;
 import com.yahoo.vespa.config.server.application.PermanentApplicationPackage;
 import com.yahoo.vespa.config.server.host.HostRegistries;
@@ -17,6 +19,7 @@ import com.yahoo.vespa.flags.FlagSource;
 
 import java.time.Clock;
 import java.util.Optional;
+import java.util.concurrent.ExecutorService;
 
 /**
  * Interface representing all global config server components used within the config server.
@@ -40,6 +43,7 @@ public interface GlobalComponentRegistry {
     Zone getZone();
     Clock getClock();
     ConfigServerDB getConfigServerDB();
+    StripedExecutor<TenantName> getZkWatcherExecutor();
     FlagSource getFlagSource();
-
+    ExecutorService getZkCacheExecutor();
 }
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/InjectedGlobalComponentRegistry.java b/configserver/src/main/java/com/yahoo/vespa/config/server/InjectedGlobalComponentRegistry.java
index f8e53350e5c..ff76afd1c98 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/InjectedGlobalComponentRegistry.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/InjectedGlobalComponentRegistry.java
@@ -3,8 +3,11 @@ package com.yahoo.vespa.config.server;
 
 import com.google.inject.Inject;
 import com.yahoo.cloud.config.ConfigserverConfig;
+import com.yahoo.concurrent.StripedExecutor;
+import com.yahoo.concurrent.ThreadFactoryFactory;
 import com.yahoo.config.model.api.ConfigDefinitionRepo;
 import com.yahoo.config.provision.Provisioner;
+import com.yahoo.config.provision.TenantName;
 import com.yahoo.config.provision.Zone;
 import com.yahoo.vespa.config.server.application.PermanentApplicationPackage;
 import com.yahoo.vespa.config.server.host.HostRegistries;
@@ -14,12 +17,15 @@ import com.yahoo.vespa.config.server.provision.HostProvisionerProvider;
 import com.yahoo.vespa.config.server.rpc.RpcServer;
 import com.yahoo.vespa.config.server.session.SessionPreparer;
 import com.yahoo.vespa.config.server.tenant.TenantListener;
+import com.yahoo.vespa.config.server.tenant.TenantRepository;
 import com.yahoo.vespa.config.server.zookeeper.ConfigCurator;
 import com.yahoo.vespa.curator.Curator;
 import com.yahoo.vespa.flags.FlagSource;
 
 import java.time.Clock;
 import java.util.Optional;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 /**
  * Registry containing all the "static"/"global" components in a config server in one place.
@@ -42,6 +48,8 @@ public class InjectedGlobalComponentRegistry implements GlobalComponentRegistry
     private final Zone zone;
     private final ConfigServerDB configServerDB;
     private final FlagSource flagSource;
+    private final StripedExecutor<TenantName> zkWatcherExecutor;
+    private final ExecutorService zkCacheExecutor;
 
     @SuppressWarnings("WeakerAccess")
     @Inject
@@ -74,6 +82,8 @@ public class InjectedGlobalComponentRegistry implements GlobalComponentRegistry
         this.zone = zone;
         this.configServerDB = configServerDB;
         this.flagSource = flagSource;
+        this.zkWatcherExecutor = new StripedExecutor<>();
+        this.zkCacheExecutor = Executors.newFixedThreadPool(1, ThreadFactoryFactory.getThreadFactory(TenantRepository.class.getName()));
     }
 
     @Override
@@ -116,5 +126,15 @@ public class InjectedGlobalComponentRegistry implements GlobalComponentRegistry
     public ConfigServerDB getConfigServerDB() { return configServerDB; }
 
     @Override
+    public StripedExecutor<TenantName> getZkWatcherExecutor() {
+        return zkWatcherExecutor;
+    }
+
+    @Override
     public FlagSource getFlagSource() { return flagSource; }
+
+    @Override
+    public ExecutorService getZkCacheExecutor() {
+        return zkCacheExecutor;
+    }
 }
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java b/configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java
index 91016e3c91b..bc33336a79b 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.config.server.application;
 
+import com.yahoo.concurrent.StripedExecutor;
 import com.yahoo.concurrent.ThreadFactoryFactory;
 import com.yahoo.config.provision.ApplicationId;
 import com.yahoo.config.provision.TenantName;
@@ -8,6 +9,7 @@ import com.yahoo.log.LogLevel;
 import com.yahoo.path.Path;
 import com.yahoo.text.Utf8;
 import com.yahoo.transaction.Transaction;
+import com.yahoo.vespa.config.server.GlobalComponentRegistry;
 import com.yahoo.vespa.config.server.ReloadHandler;
 import com.yahoo.vespa.config.server.tenant.TenantRepository;
 import com.yahoo.vespa.curator.Curator;
@@ -25,6 +27,7 @@ import java.util.Optional;
 import java.util.OptionalLong;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.logging.Logger;
@@ -48,26 +51,27 @@ public class TenantApplications {
     private final Curator curator;
     private final Path applicationsPath;
     private final Path locksPath;
-    // One thread pool for all instances of this class
-    private static final ExecutorService pathChildrenExecutor =
-            Executors.newCachedThreadPool(ThreadFactoryFactory.getDaemonThreadFactory(TenantApplications.class.getName()));
     private final Curator.DirectoryCache directoryCache;
     private final ReloadHandler reloadHandler;
     private final Map<ApplicationId, Lock> locks;
+    private final Executor zkWatcherExecutor;
 
-    private TenantApplications(Curator curator, ReloadHandler reloadHandler, TenantName tenant) {
+    private TenantApplications(Curator curator, ReloadHandler reloadHandler, TenantName tenant,
+                               ExecutorService zkCacheExecutor, StripedExecutor<TenantName> zkWatcherExecutor) {
         this.curator = curator;
         this.applicationsPath = TenantRepository.getApplicationsPath(tenant);
         this.locksPath = TenantRepository.getLocksPath(tenant);
         this.locks = new ConcurrentHashMap<>(2);
         this.reloadHandler = reloadHandler;
-        this.directoryCache = curator.createDirectoryCache(applicationsPath.getAbsolute(), false, false, pathChildrenExecutor);
+        this.zkWatcherExecutor = command -> zkWatcherExecutor.execute(tenant, command);
+        this.directoryCache = curator.createDirectoryCache(applicationsPath.getAbsolute(), false, false, zkCacheExecutor);
         this.directoryCache.start();
         this.directoryCache.addListener(this::childEvent);
     }
 
-    public static TenantApplications create(Curator curator, ReloadHandler reloadHandler, TenantName tenant) {
-        return new TenantApplications(curator, reloadHandler, tenant);
+    public static TenantApplications create(GlobalComponentRegistry registry, ReloadHandler reloadHandler, TenantName tenant) {
+        return new TenantApplications(registry.getCurator(), reloadHandler, tenant,
+                                      registry.getZkCacheExecutor(), registry.getZkWatcherExecutor());
     }
 
     /**
@@ -179,23 +183,25 @@ public class TenantApplications {
     }
 
     private void childEvent(CuratorFramework client, PathChildrenCacheEvent event) {
-        switch (event.getType()) {
-            case CHILD_ADDED:
-                applicationAdded(ApplicationId.fromSerializedForm(Path.fromString(event.getData().getPath()).getName()));
-                break;
-            // Event CHILD_REMOVED will be triggered on all config servers if deleteApplication() above is called on one of them
-            case CHILD_REMOVED:
-                applicationRemoved(ApplicationId.fromSerializedForm(Path.fromString(event.getData().getPath()).getName()));
-                break;
-            case CHILD_UPDATED:
-                // do nothing, application just got redeployed
-                break;
-            default:
-                break;
-        }
-        // We may have lost events and may need to remove applications.
-        // New applications are added when session is added, not here. See RemoteSessionRepo.
-        removeUnusedApplications();
+        zkWatcherExecutor.execute(() -> {
+            switch (event.getType()) {
+                case CHILD_ADDED:
+                    applicationAdded(ApplicationId.fromSerializedForm(Path.fromString(event.getData().getPath()).getName()));
+                    break;
+                // Event CHILD_REMOVED will be triggered on all config servers if deleteApplication() above is called on one of them
+                case CHILD_REMOVED:
+                    applicationRemoved(ApplicationId.fromSerializedForm(Path.fromString(event.getData().getPath()).getName()));
+                    break;
+                case CHILD_UPDATED:
+                    // do nothing, application just got redeployed
+                    break;
+                default:
+                    break;
+            }
+            // We may have lost events and may need to remove applications.
+            // New applications are added when session is added, not here. See RemoteSessionRepo.
+            removeUnusedApplications();
+        });
     }
 
     private void applicationRemoved(ApplicationId applicationId) {
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/LocalSessionRepo.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/LocalSessionRepo.java
index acfd81b33bf..f6d73f33504 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/LocalSessionRepo.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/LocalSessionRepo.java
@@ -1,9 +1,13 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.config.server.session;
 
+import com.yahoo.concurrent.InThreadExecutorService;
+import com.yahoo.concurrent.StripedExecutor;
+import com.yahoo.config.provision.TenantName;
 import com.yahoo.log.LogLevel;
 import com.yahoo.path.Path;
 import com.yahoo.transaction.NestedTransaction;
+import com.yahoo.vespa.config.server.GlobalComponentRegistry;
 import com.yahoo.vespa.config.server.deploy.TenantFileSystemDirs;
 import com.yahoo.vespa.config.server.tenant.TenantRepository;
 import com.yahoo.vespa.config.server.zookeeper.ConfigCurator;
@@ -12,10 +16,12 @@ import com.yahoo.vespa.curator.Curator;
 import java.io.File;
 import java.io.FilenameFilter;
 import java.time.Clock;
+import java.time.Duration;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.Executor;
 import java.util.concurrent.TimeUnit;
 import java.util.logging.Logger;
 
@@ -33,23 +39,24 @@ public class LocalSessionRepo extends SessionRepo<LocalSession> {
     private final long sessionLifetime; // in seconds
     private final Clock clock;
     private final Curator curator;
+    private final Executor zkWatcherExecutor;
 
-    public LocalSessionRepo(TenantFileSystemDirs tenantFileSystemDirs, LocalSessionLoader loader,
-                            Clock clock, long sessionLifeTime, Curator curator) {
-        this(clock, curator, sessionLifeTime);
+    public LocalSessionRepo(TenantName tenantName, GlobalComponentRegistry registry, TenantFileSystemDirs tenantFileSystemDirs, LocalSessionLoader loader) {
+        this(registry.getClock(), registry.getCurator(), registry.getConfigserverConfig().sessionLifetime(),
+             command -> registry.getZkWatcherExecutor().execute(tenantName, command));
         loadSessions(tenantFileSystemDirs.sessionsPath(), loader);
     }
 
     // Constructor public only for testing
     public LocalSessionRepo(Clock clock, Curator curator) {
-        this(clock, curator, TimeUnit.DAYS.toMillis(1));
+        this(clock, curator, Duration.ofDays(1).toMillis(), Runnable::run);
     }
 
-    // Constructor public only for testing
-    private LocalSessionRepo(Clock clock, Curator curator, long sessionLifetime) {
+    private LocalSessionRepo(Clock clock, Curator curator, long sessionLifetime, Executor zkWatcherExecutor) {
         this.clock = clock;
         this.curator = curator;
         this.sessionLifetime = sessionLifetime;
+        this.zkWatcherExecutor = zkWatcherExecutor;
     }
 
     @Override
@@ -58,7 +65,7 @@ public class LocalSessionRepo extends SessionRepo<LocalSession> {
         Path sessionsPath = TenantRepository.getSessionsPath(session.getTenantName());
         long sessionId = session.getSessionId();
         Curator.FileCache fileCache = curator.createFileCache(sessionsPath.append(String.valueOf(sessionId)).append(ConfigCurator.SESSIONSTATE_ZK_SUBPATH).getAbsolute(), false);
-        sessionStateWatchers.put(sessionId, new LocalSessionStateWatcher(fileCache, session, this));
+        sessionStateWatchers.put(sessionId, new LocalSessionStateWatcher(fileCache, session, this, zkWatcherExecutor));
     }
 
     private void loadSessions(File applicationsDir, LocalSessionLoader loader) {
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/LocalSessionStateWatcher.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/LocalSessionStateWatcher.java
index 37082888d70..53a472c2b67 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/LocalSessionStateWatcher.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/LocalSessionStateWatcher.java
@@ -2,11 +2,11 @@
 package com.yahoo.vespa.config.server.session;
 
 import com.yahoo.concurrent.ThreadFactoryFactory;
+import com.yahoo.config.provision.TenantName;
 import com.yahoo.log.LogLevel;
 import com.yahoo.text.Utf8;
 import com.yahoo.vespa.curator.Curator;
 import org.apache.curator.framework.recipes.cache.ChildData;
-import org.apache.curator.framework.recipes.cache.NodeCacheListener;
 
 import java.util.concurrent.Executor;
 import java.util.concurrent.Executors;
@@ -21,17 +21,18 @@ import java.util.logging.Logger;
 public class LocalSessionStateWatcher {
 
     private static final Logger log = Logger.getLogger(LocalSessionStateWatcher.class.getName());
-    // One thread pool for all instances of this class
-    private static final Executor executor = Executors.newCachedThreadPool(ThreadFactoryFactory.getDaemonThreadFactory(LocalSessionStateWatcher.class.getName()));
 
     private final Curator.FileCache fileCache;
     private final LocalSession session;
     private final LocalSessionRepo localSessionRepo;
+    private final Executor zkWatcherExecutor;
 
-    LocalSessionStateWatcher(Curator.FileCache fileCache, LocalSession session, LocalSessionRepo localSessionRepo) {
+    LocalSessionStateWatcher(Curator.FileCache fileCache, LocalSession session,
+                             LocalSessionRepo localSessionRepo, Executor zkWatcherExecutor) {
         this.fileCache = fileCache;
         this.session = session;
         this.localSessionRepo = localSessionRepo;
+        this.zkWatcherExecutor = zkWatcherExecutor;
         this.fileCache.start();
         this.fileCache.addListener(this::nodeChanged);
     }
@@ -60,7 +61,7 @@ public class LocalSessionStateWatcher {
     }
 
     public void nodeChanged() {
-        executor.execute(() -> {
+        zkWatcherExecutor.execute(() -> {
             try {
                 ChildData data = fileCache.getCurrentData();
                 if (data != null) {
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSessionRepo.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSessionRepo.java
index 27e1a7e43b4..24eb862c528 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSessionRepo.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSessionRepo.java
@@ -3,14 +3,18 @@ package com.yahoo.vespa.config.server.session;
 
 import com.google.common.collect.HashMultiset;
 import com.google.common.collect.Multiset;
+import com.yahoo.concurrent.InThreadExecutorService;
+import com.yahoo.concurrent.StripedExecutor;
 import com.yahoo.concurrent.ThreadFactoryFactory;
 import com.yahoo.config.provision.ApplicationId;
 import com.yahoo.config.provision.TenantName;
 import com.yahoo.log.LogLevel;
 import com.yahoo.path.Path;
+import com.yahoo.vespa.config.server.GlobalComponentRegistry;
 import com.yahoo.vespa.config.server.ReloadHandler;
 import com.yahoo.vespa.config.server.application.TenantApplications;
 import com.yahoo.vespa.config.server.monitoring.MetricUpdater;
+import com.yahoo.vespa.config.server.monitoring.Metrics;
 import com.yahoo.vespa.config.server.tenant.TenantRepository;
 import com.yahoo.vespa.config.server.zookeeper.ConfigCurator;
 import com.yahoo.vespa.curator.Curator;
@@ -28,6 +32,7 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.logging.Level;
@@ -45,9 +50,6 @@ import java.util.stream.Collectors;
 public class RemoteSessionRepo extends SessionRepo<RemoteSession> {
 
     private static final Logger log = Logger.getLogger(RemoteSessionRepo.class.getName());
-    // One thread pool for all instances of this class
-    private static final ExecutorService pathChildrenExecutor =
-            Executors.newCachedThreadPool(ThreadFactoryFactory.getDaemonThreadFactory(RemoteSessionRepo.class.getName()));
 
     private final Curator curator;
     private final Path sessionsPath;
@@ -59,31 +61,26 @@ public class RemoteSessionRepo extends SessionRepo<RemoteSession> {
     private final FlagSource flagSource;
     private final Curator.DirectoryCache directoryCache;
     private final TenantApplications applicationRepo;
+    private final Executor zkWatcherExecutor;
 
-    /**
-     * @param curator              a {@link Curator} instance.
-     * @param remoteSessionFactory a {@link com.yahoo.vespa.config.server.session.RemoteSessionFactory}
-     * @param reloadHandler        a {@link com.yahoo.vespa.config.server.ReloadHandler}
-     * @param tenantName           a {@link TenantName} instance.
-     * @param applicationRepo      a {@link TenantApplications} instance.
-     */
-    public RemoteSessionRepo(Curator curator,
+    public RemoteSessionRepo(GlobalComponentRegistry registry,
                              RemoteSessionFactory remoteSessionFactory,
                              ReloadHandler reloadHandler,
                              TenantName tenantName,
-                             TenantApplications applicationRepo,
-                             MetricUpdater metricUpdater,
-                             FlagSource flagSource) {
-        this.curator = curator;
+                             TenantApplications applicationRepo) {
+
+        this.curator = registry.getCurator();
         this.sessionsPath = TenantRepository.getSessionsPath(tenantName);
         this.applicationRepo = applicationRepo;
         this.remoteSessionFactory = remoteSessionFactory;
         this.reloadHandler = reloadHandler;
         this.tenantName = tenantName;
-        this.metrics = metricUpdater;
-        this.flagSource = flagSource;
+        this.metrics = registry.getMetrics().getOrCreateMetricUpdater(Metrics.createDimensions(tenantName));
+        this.flagSource = registry.getFlagSource();
+        StripedExecutor<TenantName> zkWatcherExecutor = registry.getZkWatcherExecutor();
+        this.zkWatcherExecutor = command -> zkWatcherExecutor.execute(tenantName, command);
         initializeSessions();
-        this.directoryCache = curator.createDirectoryCache(sessionsPath.getAbsolute(), false, false, pathChildrenExecutor);
+        this.directoryCache = curator.createDirectoryCache(sessionsPath.getAbsolute(), false, false, registry.getZkCacheExecutor());
         this.directoryCache.addListener(this::childEvent);
         this.directoryCache.start();
     }
@@ -99,6 +96,7 @@ public class RemoteSessionRepo extends SessionRepo<RemoteSession> {
         this.directoryCache = null;
         this.applicationRepo = null;
         this.flagSource = new InMemoryFlagSource();
+        this.zkWatcherExecutor = Runnable::run;
     }
 
     public List<Long> getSessions() {
@@ -168,7 +166,7 @@ public class RemoteSessionRepo extends SessionRepo<RemoteSession> {
             Curator.FileCache fileCache = curator.createFileCache(sessionPath.append(ConfigCurator.SESSIONSTATE_ZK_SUBPATH).getAbsolute(), false);
             fileCache.addListener(this::nodeChanged);
             loadSessionIfActive(session);
-            sessionStateWatchers.put(sessionId, new RemoteSessionStateWatcher(fileCache, reloadHandler, session, metrics));
+            sessionStateWatchers.put(sessionId, new RemoteSessionStateWatcher(fileCache, reloadHandler, session, metrics, zkWatcherExecutor));
             addSession(session);
             metrics.incAddedSessions();
         } catch (Exception e) {
@@ -208,31 +206,35 @@ public class RemoteSessionRepo extends SessionRepo<RemoteSession> {
     }
 
     private void nodeChanged() {
-        Multiset<Session.Status> sessionMetrics = HashMultiset.create();
-        for (RemoteSession session : listSessions()) {
-            sessionMetrics.add(session.getStatus());
-        }
-        metrics.setNewSessions(sessionMetrics.count(Session.Status.NEW));
-        metrics.setPreparedSessions(sessionMetrics.count(Session.Status.PREPARE));
-        metrics.setActivatedSessions(sessionMetrics.count(Session.Status.ACTIVATE));
-        metrics.setDeactivatedSessions(sessionMetrics.count(Session.Status.DEACTIVATE));
+        zkWatcherExecutor.execute(() -> {
+            Multiset<Session.Status> sessionMetrics = HashMultiset.create();
+            for (RemoteSession session : listSessions()) {
+                sessionMetrics.add(session.getStatus());
+            }
+            metrics.setNewSessions(sessionMetrics.count(Session.Status.NEW));
+            metrics.setPreparedSessions(sessionMetrics.count(Session.Status.PREPARE));
+            metrics.setActivatedSessions(sessionMetrics.count(Session.Status.ACTIVATE));
+            metrics.setDeactivatedSessions(sessionMetrics.count(Session.Status.DEACTIVATE));
+        });
     }
 
     @SuppressWarnings("unused")
     private void childEvent(CuratorFramework ignored, PathChildrenCacheEvent event) {
-        log.log(LogLevel.DEBUG, () -> "Got child event: " + event);
-        switch (event.getType()) {
-            case CHILD_ADDED:
-                sessionsChanged();
-                synchronizeOnNew(getSessionListFromDirectoryCache(Collections.singletonList(event.getData())));
-                break;
-            case CHILD_REMOVED:
-                sessionsChanged();
-                break;
-            case CONNECTION_RECONNECTED:
-                sessionsChanged();
-                break;
-        }
+        zkWatcherExecutor.execute(() -> {
+            log.log(LogLevel.DEBUG, () -> "Got child event: " + event);
+            switch (event.getType()) {
+                case CHILD_ADDED:
+                    sessionsChanged();
+                    synchronizeOnNew(getSessionListFromDirectoryCache(Collections.singletonList(event.getData())));
+                    break;
+                case CHILD_REMOVED:
+                    sessionsChanged();
+                    break;
+                case CONNECTION_RECONNECTED:
+                    sessionsChanged();
+                    break;
+            }
+        });
     }
 
     private void synchronizeOnNew(List<Long> sessionList) {
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSessionStateWatcher.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSessionStateWatcher.java
index ef59e28f458..653a2616cbe 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSessionStateWatcher.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSessionStateWatcher.java
@@ -1,17 +1,16 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.config.server.session;
 
-import com.yahoo.concurrent.ThreadFactoryFactory;
+import com.yahoo.concurrent.StripedExecutor;
+import com.yahoo.config.provision.TenantName;
 import com.yahoo.log.LogLevel;
 import com.yahoo.text.Utf8;
 import com.yahoo.vespa.config.server.ReloadHandler;
 import com.yahoo.vespa.config.server.monitoring.MetricUpdater;
 import com.yahoo.vespa.curator.Curator;
 import org.apache.curator.framework.recipes.cache.ChildData;
-import org.apache.curator.framework.recipes.cache.NodeCacheListener;
 
 import java.util.concurrent.Executor;
-import java.util.concurrent.Executors;
 import java.util.logging.Logger;
 
 /**
@@ -24,24 +23,25 @@ public class RemoteSessionStateWatcher {
 
     private static final Logger log = Logger.getLogger(RemoteSessionStateWatcher.class.getName());
     // One thread pool for all instances of this class
-    private static final Executor executor = Executors.newCachedThreadPool(ThreadFactoryFactory.getDaemonThreadFactory(RemoteSessionStateWatcher.class.getName()));
 
     private final Curator.FileCache fileCache;
     private final ReloadHandler reloadHandler;
     private final RemoteSession session;
     private final MetricUpdater metrics;
-
+    private final Executor zkWatcherExecutor;
 
     RemoteSessionStateWatcher(Curator.FileCache fileCache,
                               ReloadHandler reloadHandler,
                               RemoteSession session,
-                              MetricUpdater metrics) {
+                              MetricUpdater metrics,
+                              Executor zkWatcherExecutor) {
         this.fileCache = fileCache;
         this.reloadHandler = reloadHandler;
         this.session = session;
         this.metrics = metrics;
         this.fileCache.start();
         this.fileCache.addListener(this::nodeChanged);
+        this.zkWatcherExecutor = zkWatcherExecutor;
     }
 
     private void sessionChanged(Session.Status status) {
@@ -73,7 +73,7 @@ public class RemoteSessionStateWatcher {
     }
 
     public void nodeChanged() {
-        executor.execute(() -> {
+        zkWatcherExecutor.execute(() -> {
             try {
                 ChildData data = fileCache.getCurrentData();
                 if (data != null) {
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/Tenant.java b/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/Tenant.java
index 88e71d7ddd1..0aed3977625 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/Tenant.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/Tenant.java
@@ -142,15 +142,20 @@ public class Tenant implements TenantHandlerProvider {
     }
 
     /**
-     * Closes any watchers, thread pools that may react to changes in tenant state, and removes any state
-     * in filesystem and zookeeper
+     * Closes any watchers, thread pools that may react to changes in tenant state,
+     * and removes any session data in filesystem and zookeeper.
+     * Called by watchers as a reaction to {@link #delete()}.
      */
-    public void close() {
-        tenantFileSystemDirs.delete();
-        remoteSessionRepo.close();
-        applicationRepo.close();
-        localSessionRepo.deleteAllSessions();
-        curator.delete(path);
+    void close() {
+        tenantFileSystemDirs.delete();          // Deletes all local files.
+        remoteSessionRepo.close();              // Closes watchers and clears memory.
+        applicationRepo.close();                // Closes watchers.
+        localSessionRepo.deleteAllSessions();   // Closes watchers, clears memory, and deletes some local files and ZK session state.
+    }
+
+    /** Deletes the tenant tree from ZooKeeper (application and session status for the tenant) and triggers {@link #close()}. */
+    void delete() {
+        curator.delete(path);                   // Deletes tenant ZK tree: applications and sessions.
     }
 
 }
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantBuilder.java b/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantBuilder.java
index 9b5da267c6e..861b2f91c8f 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantBuilder.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantBuilder.java
@@ -98,9 +98,7 @@ public class TenantBuilder {
 
 	private void createLocalSessionRepo() {
         if (localSessionRepo == null) {
-            localSessionRepo = new LocalSessionRepo(tenantFileSystemDirs, localSessionLoader, componentRegistry.getClock(),
-                                                    componentRegistry.getConfigserverConfig().sessionLifetime(),
-                                                    componentRegistry.getCurator());
+            localSessionRepo = new LocalSessionRepo(tenant, componentRegistry, tenantFileSystemDirs, localSessionLoader);
         }
     }
 
@@ -129,8 +127,7 @@ public class TenantBuilder {
                                                                  tenant,
                                                                  Collections.singletonList(componentRegistry.getReloadListener()),
                                                                  ConfigResponseFactory.create(componentRegistry.getConfigserverConfig()),
-                                                                 componentRegistry.getHostRegistries(),
-                                                                 componentRegistry.getCurator());
+                                                                 componentRegistry);
             if (hostValidator == null) {
                 this.hostValidator = impl;
             }
@@ -149,13 +146,12 @@ public class TenantBuilder {
 
     private void createRemoteSessionRepo() {
         if (remoteSessionRepo == null) {
-            remoteSessionRepo = new RemoteSessionRepo(componentRegistry.getCurator(),
-                    remoteSessionFactory,
-                    reloadHandler,
-                    tenant,
-                    applicationRepo,
-                    componentRegistry.getMetrics().getOrCreateMetricUpdater(Metrics.createDimensions(tenant)),
-                    componentRegistry.getFlagSource());
+            remoteSessionRepo = new RemoteSessionRepo(componentRegistry,
+                                                      remoteSessionFactory,
+                                                      reloadHandler,
+                                                      tenant,
+                                                      applicationRepo);
+
         }
     }
 
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantRepository.java b/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantRepository.java
index 53d01fdf933..ad2472add89 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantRepository.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantRepository.java
@@ -4,6 +4,7 @@ package com.yahoo.vespa.config.server.tenant;
 import com.google.common.collect.ImmutableSet;
 import com.google.inject.Inject;
 import com.yahoo.cloud.config.ConfigserverConfig;
+import com.yahoo.concurrent.StripedExecutor;
 import com.yahoo.concurrent.ThreadFactoryFactory;
 import com.yahoo.config.provision.ApplicationId;
 import com.yahoo.config.provision.TenantName;
@@ -73,7 +74,8 @@ public class TenantRepository {
     private final Curator curator;
 
     private final MetricUpdater metricUpdater;
-    private final ExecutorService pathChildrenExecutor = Executors.newFixedThreadPool(1, ThreadFactoryFactory.getThreadFactory(TenantRepository.class.getName()));
+    private final ExecutorService zkCacheExecutor;
+    private final StripedExecutor<TenantName> zkWatcherExecutor;
     private final ExecutorService bootstrapExecutor;
     private final ScheduledExecutorService checkForRemovedApplicationsService = new ScheduledThreadPoolExecutor(1);
     private final Optional<Curator.DirectoryCache> directoryCache;
@@ -104,6 +106,8 @@ public class TenantRepository {
         this.curator = globalComponentRegistry.getCurator();
         metricUpdater = globalComponentRegistry.getMetrics().getOrCreateMetricUpdater(Collections.emptyMap());
         this.tenantListeners.add(globalComponentRegistry.getTenantListener());
+        this.zkCacheExecutor = globalComponentRegistry.getZkCacheExecutor();
+        this.zkWatcherExecutor = globalComponentRegistry.getZkWatcherExecutor();
         curator.framework().getConnectionStateListenable().addListener(this::stateChanged);
 
         curator.create(tenantsPath);
@@ -112,7 +116,7 @@ public class TenantRepository {
         curator.create(vespaPath);
 
         if (useZooKeeperWatchForTenantChanges) {
-            this.directoryCache = Optional.of(curator.createDirectoryCache(tenantsPath.getAbsolute(), false, false, pathChildrenExecutor));
+            this.directoryCache = Optional.of(curator.createDirectoryCache(tenantsPath.getAbsolute(), false, false, zkCacheExecutor));
             this.directoryCache.get().start();
             this.directoryCache.get().addListener(this::childEvent);
         } else {
@@ -147,22 +151,19 @@ public class TenantRepository {
         return curator.getChildren(tenantsPath).stream().map(TenantName::from).collect(Collectors.toSet());
     }
 
-    private synchronized void updateTenants() {
+    /** Public for testing. */
+    public synchronized void updateTenants() {
         Set<TenantName> allTenants = readTenantsFromZooKeeper(curator);
         log.log(LogLevel.DEBUG, "Create tenants, tenants found in zookeeper: " + allTenants);
-        checkForRemovedTenants(allTenants);
-        allTenants.stream().filter(tenantName -> ! tenants.containsKey(tenantName)).forEach(this::createTenant);
+        for (TenantName tenantName : Set.copyOf(tenants.keySet()))
+            if ( ! allTenants.contains(tenantName))
+                zkWatcherExecutor.execute(tenantName, () -> closeTenant(tenantName));
+        for (TenantName tenantName : allTenants)
+            if ( ! tenants.containsKey(tenantName))
+                zkWatcherExecutor.execute(tenantName, () -> createTenant(tenantName));
         metricUpdater.setTenants(tenants.size());
     }
 
-    private void checkForRemovedTenants(Set<TenantName> newTenants) {
-        for (TenantName tenantName : ImmutableSet.copyOf(tenants.keySet())) {
-            if (!newTenants.contains(tenantName)) {
-                deleteTenant(tenantName);
-            }
-        }
-    }
-
     private void bootstrapTenants() {
         // Keep track of tenants created
         Map<TenantName, Future<?>> futures = new HashMap<>();
@@ -273,19 +274,25 @@ public class TenantRepository {
      * Removes the given tenant from ZooKeeper and filesystem. Assumes that tenant exists.
      *
      * @param name name of the tenant
-     * @return this TenantRepository instance
      */
-    public synchronized TenantRepository deleteTenant(TenantName name) {
+    public synchronized void deleteTenant(TenantName name) {
         if (name.equals(DEFAULT_TENANT))
             throw new IllegalArgumentException("Deleting 'default' tenant is not allowed");
+        if ( ! tenants.containsKey(name))
+            throw new IllegalArgumentException("Deleting '" + name + "' failed, tenant does not exist");
+
         log.log(LogLevel.INFO, "Deleting tenant '" + name + "'");
+        tenants.get(name).delete();
+    }
+
+    public synchronized void closeTenant(TenantName name) {
         Tenant tenant = tenants.remove(name);
-        if (tenant == null) {
-            throw new IllegalArgumentException("Deleting '" + name + "' failed, tenant does not exist");
-        }
+        if (tenant == null)
+            throw new IllegalArgumentException("Closing '" + name + "' failed, tenant does not exist");
+
+        log.log(LogLevel.INFO, "Closing tenant '" + name + "'");
         notifyRemovedTenant(name);
         tenant.close();
-        return this;
     }
 
     // For unit testing
@@ -353,9 +360,10 @@ public class TenantRepository {
     public void close() {
         directoryCache.ifPresent(Curator.DirectoryCache::close);
         try {
-            pathChildrenExecutor.shutdown();
+            zkCacheExecutor.shutdown();
             checkForRemovedApplicationsService.shutdown();
-            pathChildrenExecutor.awaitTermination(50, TimeUnit.SECONDS);
+            zkWatcherExecutor.shutdownAndWait();
+            zkCacheExecutor.awaitTermination(50, TimeUnit.SECONDS);
             checkForRemovedApplicationsService.awaitTermination(50, TimeUnit.SECONDS);
         }
         catch (InterruptedException e) {
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantRequestHandler.java b/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantRequestHandler.java
index 65b92558216..2f9a5eb9277 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantRequestHandler.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantRequestHandler.java
@@ -2,6 +2,7 @@
 package com.yahoo.vespa.config.server.tenant;
 
 import com.yahoo.component.Version;
+import com.yahoo.concurrent.StripedExecutor;
 import com.yahoo.config.FileReference;
 import com.yahoo.config.provision.ApplicationId;
 import com.yahoo.config.provision.TenantName;
@@ -9,6 +10,7 @@ import com.yahoo.log.LogLevel;
 import com.yahoo.vespa.config.ConfigKey;
 import com.yahoo.vespa.config.GetConfigRequest;
 import com.yahoo.vespa.config.protocol.ConfigResponse;
+import com.yahoo.vespa.config.server.GlobalComponentRegistry;
 import com.yahoo.vespa.config.server.NotFoundException;
 import com.yahoo.vespa.config.server.ReloadHandler;
 import com.yahoo.vespa.config.server.ReloadListener;
@@ -33,6 +35,7 @@ import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Optional;
 import java.util.Set;
+import java.util.concurrent.ExecutorService;
 
 import static java.util.stream.Collectors.toSet;
 
@@ -60,15 +63,15 @@ public class TenantRequestHandler implements RequestHandler, ReloadHandler, Host
                                 TenantName tenant,
                                 List<ReloadListener> reloadListeners,
                                 ConfigResponseFactory responseFactory,
-                                HostRegistries hostRegistries,
-                                Curator curator) { // TODO jvenstad: Merge this class with TenantApplications, and straighten this out.
+                                GlobalComponentRegistry registry) { // TODO jvenstad: Merge this class with TenantApplications, and straighten this out.
         this.metrics = metrics;
         this.tenant = tenant;
         this.reloadListeners = List.copyOf(reloadListeners);
         this.responseFactory = responseFactory;
         this.tenantMetricUpdater = metrics.getOrCreateMetricUpdater(Metrics.createDimensions(tenant));
-        this.hostRegistry = hostRegistries.createApplicationHostRegistry(tenant);
-        this.applications = TenantApplications.create(curator, this, tenant);
+        this.hostRegistry = registry.getHostRegistries().createApplicationHostRegistry(tenant);
+        this.applications = TenantApplications.create(registry, this, tenant);
+
     }
 
     /**
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/TestComponentRegistry.java b/configserver/src/test/java/com/yahoo/vespa/config/server/TestComponentRegistry.java
index e369d5bd3bb..62685734a47 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/TestComponentRegistry.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/TestComponentRegistry.java
@@ -3,9 +3,13 @@ package com.yahoo.vespa.config.server;
 
 import com.google.common.io.Files;
 import com.yahoo.cloud.config.ConfigserverConfig;
+import com.yahoo.concurrent.InThreadExecutorService;
+import com.yahoo.concurrent.StripedExecutor;
+import com.yahoo.concurrent.ThreadFactoryFactory;
 import com.yahoo.config.model.NullConfigModelRegistry;
 import com.yahoo.config.model.api.ConfigDefinitionRepo;
 import com.yahoo.config.provision.Provisioner;
+import com.yahoo.config.provision.TenantName;
 import com.yahoo.config.provision.Zone;
 import com.yahoo.vespa.config.server.application.PermanentApplicationPackage;
 import com.yahoo.vespa.config.server.host.HostRegistries;
@@ -17,6 +21,7 @@ import com.yahoo.vespa.config.server.session.MockFileDistributionFactory;
 import com.yahoo.vespa.config.server.session.SessionPreparer;
 import com.yahoo.vespa.config.server.tenant.MockTenantListener;
 import com.yahoo.vespa.config.server.tenant.TenantListener;
+import com.yahoo.vespa.config.server.tenant.TenantRepository;
 import com.yahoo.vespa.config.server.tenant.TenantRequestHandlerTest;
 import com.yahoo.vespa.config.server.zookeeper.ConfigCurator;
 import com.yahoo.vespa.curator.Curator;
@@ -28,6 +33,8 @@ import com.yahoo.vespa.model.VespaModelFactory;
 import java.time.Clock;
 import java.util.Collections;
 import java.util.Optional;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 
 /**
@@ -51,6 +58,8 @@ public class TestComponentRegistry implements GlobalComponentRegistry {
     private final Zone zone;
     private final Clock clock;
     private final ConfigServerDB configServerDB;
+    private final StripedExecutor<TenantName> zkWatcherExecutor;
+    private final ExecutorService zkCacheExecutor;
 
     private TestComponentRegistry(Curator curator, ConfigCurator configCurator, Metrics metrics,
                                   ModelFactoryRegistry modelFactoryRegistry,
@@ -81,6 +90,8 @@ public class TestComponentRegistry implements GlobalComponentRegistry {
         this.zone = zone;
         this.clock = clock;
         this.configServerDB = new ConfigServerDB(configserverConfig);
+        this.zkWatcherExecutor = new StripedExecutor<>(new InThreadExecutorService());
+        this.zkCacheExecutor = new InThreadExecutorService();
     }
 
     public static class Builder {
@@ -90,6 +101,7 @@ public class TestComponentRegistry implements GlobalComponentRegistry {
         private ConfigserverConfig configserverConfig = new ConfigserverConfig(
                 new ConfigserverConfig.Builder()
                         .configServerDBDir(Files.createTempDir().getAbsolutePath())
+                        .sessionLifetime(5)
                         .configDefinitionsDir(Files.createTempDir().getAbsolutePath()));
         private ConfigDefinitionRepo defRepo = new StaticConfigDefinitionRepo();
         private TenantRequestHandlerTest.MockReloadListener reloadListener = new TenantRequestHandlerTest.MockReloadListener();
@@ -194,9 +206,20 @@ public class TestComponentRegistry implements GlobalComponentRegistry {
     public Clock getClock() { return clock;}
     @Override
     public ConfigServerDB getConfigServerDB() { return configServerDB;}
+
+    @Override
+    public StripedExecutor<TenantName> getZkWatcherExecutor() {
+        return zkWatcherExecutor;
+    }
+
     @Override
     public FlagSource getFlagSource() { return new InMemoryFlagSource(); }
 
+    @Override
+    public ExecutorService getZkCacheExecutor() {
+        return zkCacheExecutor;
+    }
+
     public FileDistributionFactory getFileDistributionFactory() { return fileDistributionFactory; }
 
 }
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/application/TenantApplicationsTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/application/TenantApplicationsTest.java
index ac7ff1e85c5..e3335dded4c 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/application/TenantApplicationsTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/application/TenantApplicationsTest.java
@@ -6,6 +6,7 @@ import com.yahoo.config.provision.TenantName;
 import com.yahoo.text.Utf8;
 import com.yahoo.vespa.config.server.MockReloadHandler;
 
+import com.yahoo.vespa.config.server.TestComponentRegistry;
 import com.yahoo.vespa.config.server.tenant.TenantRepository;
 import com.yahoo.vespa.curator.Curator;
 import com.yahoo.vespa.curator.mock.MockCurator;
@@ -115,7 +116,7 @@ public class TenantApplicationsTest {
     }
 
     private TenantApplications createZKAppRepo(MockReloadHandler reloadHandler) {
-        return TenantApplications.create(curator, reloadHandler, tenantName);
+        return TenantApplications.create(new TestComponentRegistry.Builder().curator(curator).build(), reloadHandler, tenantName);
     }
 
     private static ApplicationId createApplicationId(String name) {
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/http/v2/SessionActiveHandlerTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/http/v2/SessionActiveHandlerTest.java
index a62a2841995..087a8c0cb8c 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/http/v2/SessionActiveHandlerTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/http/v2/SessionActiveHandlerTest.java
@@ -105,7 +105,7 @@ public class SessionActiveHandlerTest extends SessionHandlerTest {
                 .modelFactoryRegistry(new ModelFactoryRegistry(Collections.singletonList(modelFactory)))
                 .build();
         tenantRepository = new TenantRepository(componentRegistry, false);
-        applicationRepo = TenantApplications.create(curator, new MockReloadHandler(), tenantName);
+        applicationRepo = TenantApplications.create(componentRegistry, new MockReloadHandler(), tenantName);
         localRepo = new LocalSessionRepo(clock, curator);
         pathPrefix = "/application/v2/tenant/" + tenantName + "/session/";
         hostProvisioner = new MockProvisioner();
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/http/v2/SessionCreateHandlerTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/http/v2/SessionCreateHandlerTest.java
index 0946ef3992c..81dd41ac714 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/http/v2/SessionCreateHandlerTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/http/v2/SessionCreateHandlerTest.java
@@ -72,7 +72,7 @@ public class SessionCreateHandlerTest extends SessionHandlerTest {
     @Before
     public void setupRepo() {
         Curator curator = new MockCurator();
-        applicationRepo = TenantApplications.create(curator, new MockReloadHandler(), tenant);
+        applicationRepo = TenantApplications.create(componentRegistry, new MockReloadHandler(), tenant);
         localSessionRepo = new LocalSessionRepo(Clock.systemUTC(), curator);
         tenantRepository = new TenantRepository(componentRegistry, false);
         sessionFactory = new MockSessionFactory();
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/http/v2/SessionPrepareHandlerTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/http/v2/SessionPrepareHandlerTest.java
index 7b0b00caa8b..a264b440af8 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/http/v2/SessionPrepareHandlerTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/http/v2/SessionPrepareHandlerTest.java
@@ -88,7 +88,7 @@ public class SessionPrepareHandlerTest extends SessionHandlerTest {
                 .withSessionFactory(new MockSessionFactory())
                 .withLocalSessionRepo(localRepo)
                 .withRemoteSessionRepo(remoteSessionRepo)
-                .withApplicationRepo(TenantApplications.create(curator, new MockReloadHandler(), tenant));
+                .withApplicationRepo(TenantApplications.create(componentRegistry, new MockReloadHandler(), tenant));
         tenantRepository.addTenant(tenantBuilder);
     }
 
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/maintenance/TenantsMaintainerTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/maintenance/TenantsMaintainerTest.java
index a2f52bc5321..fdc6ffeacf0 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/maintenance/TenantsMaintainerTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/maintenance/TenantsMaintainerTest.java
@@ -37,6 +37,7 @@ public class TenantsMaintainerTest {
         assertNotNull(tenantRepository.getTenant(shouldNotBeDeleted));
 
         new TenantsMaintainer(applicationRepository, tester.curator(), Duration.ofDays(1)).run();
+        tenantRepository.updateTenants();
 
         // One tenant should now have been deleted
         assertNull(tenantRepository.getTenant(shouldBeDeleted));
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/session/LocalSessionRepoTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/session/LocalSessionRepoTest.java
index 3626c6269cc..d3f364e30ac 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/session/LocalSessionRepoTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/session/LocalSessionRepoTest.java
@@ -46,7 +46,6 @@ public class LocalSessionRepoTest {
     }
 
     private void setupSessions(TenantName tenantName, boolean createInitialSessions) throws Exception {
-        GlobalComponentRegistry globalComponentRegistry = new TestComponentRegistry.Builder().curator(new MockCurator()).build();
         TenantFileSystemDirs tenantFileSystemDirs = new TenantFileSystemDirs(temporaryFolder.newFolder(), tenantName);
         if (createInitialSessions) {
             IOUtils.copyDirectory(testApp, new File(tenantFileSystemDirs.sessionsPath(), "1"));
@@ -54,11 +53,14 @@ public class LocalSessionRepoTest {
             IOUtils.copyDirectory(testApp, new File(tenantFileSystemDirs.sessionsPath(), "3"));
         }
         clock = new ManualClock(Instant.ofEpochSecond(1));
+        GlobalComponentRegistry globalComponentRegistry = new TestComponentRegistry.Builder().curator(new MockCurator())
+                                                                                             .clock(clock)
+                                                                                             .build();
         LocalSessionLoader loader = new SessionFactoryImpl(globalComponentRegistry,
-                                                           TenantApplications.create(new MockCurator(), new MockReloadHandler(), tenantName),
+                                                           TenantApplications.create(globalComponentRegistry, new MockReloadHandler(), tenantName),
                                                            tenantFileSystemDirs, new HostRegistry<>(),
                                                            tenantName);
-        repo = new LocalSessionRepo(tenantFileSystemDirs, loader, clock, 5, globalComponentRegistry.getCurator());
+        repo = new LocalSessionRepo(tenantName, globalComponentRegistry, tenantFileSystemDirs, loader);
     }
 
     @Test
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/session/LocalSessionTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/session/LocalSessionTest.java
index d7f0914c4cf..96caff9b3a7 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/session/LocalSessionTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/session/LocalSessionTest.java
@@ -16,7 +16,7 @@ import com.yahoo.path.Path;
 import com.yahoo.slime.Slime;
 import com.yahoo.transaction.NestedTransaction;
 import com.yahoo.vespa.config.server.MockReloadHandler;
-import com.yahoo.vespa.config.server.SuperModelGenerationCounter;
+import com.yahoo.vespa.config.server.TestComponentRegistry;
 import com.yahoo.vespa.config.server.application.TenantApplications;
 import com.yahoo.vespa.config.server.deploy.DeployHandlerLogger;
 import com.yahoo.vespa.config.server.deploy.TenantFileSystemDirs;
@@ -192,7 +192,7 @@ public class LocalSessionTest {
         zkClient.write(Collections.singletonMap(new Version(0, 0, 0), new MockFileRegistry()));
         File sessionDir = new File(tenantFileSystemDirs.sessionsPath(), String.valueOf(sessionId));
         sessionDir.createNewFile();
-        TenantApplications applications = TenantApplications.create(curator, new MockReloadHandler(), tenant);
+        TenantApplications applications = TenantApplications.create(new TestComponentRegistry.Builder().curator(curator).build(), new MockReloadHandler(), tenant);
         applications.createApplication(zkc.readApplicationId());
         return new LocalSession(tenant, sessionId, preparer,
                 new SessionContext(
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/session/RemoteSessionRepoTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/session/RemoteSessionRepoTest.java
index 9dda653dbc1..83183a27666 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/session/RemoteSessionRepoTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/session/RemoteSessionRepoTest.java
@@ -10,6 +10,7 @@ import com.yahoo.config.provision.TenantName;
 import com.yahoo.path.Path;
 import com.yahoo.text.Utf8;
 
+import com.yahoo.vespa.config.server.GlobalComponentRegistry;
 import com.yahoo.vespa.config.server.MockReloadHandler;
 import com.yahoo.vespa.config.server.TestComponentRegistry;
 import com.yahoo.vespa.config.server.application.TenantApplications;
@@ -100,11 +101,12 @@ public class RemoteSessionRepoTest {
     public void testBadApplicationRepoOnActivate() {
         long sessionId = 3L;
         TenantName mytenant = TenantName.from("mytenant");
-        TenantApplications applicationRepo = TenantApplications.create(curator, new MockReloadHandler(), mytenant);
+        GlobalComponentRegistry registry = new TestComponentRegistry.Builder().curator(curator).build();
+        TenantApplications applicationRepo = TenantApplications.create(registry, new MockReloadHandler(), mytenant);
         curator.set(TenantRepository.getApplicationsPath(mytenant).append("mytenant:appX:default"), new byte[0]); // Invalid data
-        Tenant tenant = TenantBuilder.create(new TestComponentRegistry.Builder().curator(curator).build(), mytenant)
-                .withApplicationRepo(applicationRepo)
-                .build();
+        Tenant tenant = TenantBuilder.create(registry, mytenant)
+                                     .withApplicationRepo(applicationRepo)
+                                     .build();
         curator.create(TenantRepository.getSessionsPath(mytenant));
         remoteSessionRepo = tenant.getRemoteSessionRepo();
         assertThat(remoteSessionRepo.listSessions().size(), is(0));
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/session/SessionPreparerTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/session/SessionPreparerTest.java
index b80149859cb..072dcf0e26f 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/session/SessionPreparerTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/session/SessionPreparerTest.java
@@ -217,7 +217,7 @@ public class SessionPreparerTest {
         return new SessionContext(app,
                                   new SessionZooKeeperClient(curator, sessionsPath),
                                   app.getAppDir(),
-                                  TenantApplications.create(curator, new MockReloadHandler(), TenantName.from("tenant")),
+                                  TenantApplications.create(componentRegistry, new MockReloadHandler(), TenantName.from("tenant")),
                                   new HostRegistry<>(),
                                   flagSource);
     }
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/tenant/TenantRequestHandlerTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/tenant/TenantRequestHandlerTest.java
index 6aa5aa7cd70..4275dc7e16a 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/tenant/TenantRequestHandlerTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/tenant/TenantRequestHandlerTest.java
@@ -93,11 +93,11 @@ public class TenantRequestHandlerTest {
         Metrics sh = Metrics.createTestMetrics();
         List<ReloadListener> listeners = new ArrayList<>();
         listeners.add(listener);
-        server = new TenantRequestHandler(sh, tenant, listeners, new UncompressedConfigResponseFactory(), new HostRegistries(), curator);
         componentRegistry = new TestComponentRegistry.Builder()
                 .curator(curator)
                 .modelFactoryRegistry(createRegistry())
                 .build();
+        server = new TenantRequestHandler(sh, tenant, listeners, new UncompressedConfigResponseFactory(), componentRegistry);
     }
 
     private void feedApp(File appDir, long sessionId, ApplicationId appId, boolean  internalRedeploy) throws IOException {
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/tenant/TenantTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/tenant/TenantTest.java
index baab250a508..e140dae3650 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/tenant/TenantTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/tenant/TenantTest.java
@@ -38,7 +38,7 @@ public class TenantTest {
         TenantRepository tenantRepository = new TenantRepository(componentRegistry, false);
         TenantName tenantName = TenantName.from(name);
         TenantBuilder tenantBuilder = TenantBuilder.create(componentRegistry, tenantName)
-                .withApplicationRepo(TenantApplications.create(new MockCurator(), new MockReloadHandler(), tenantName));
+                .withApplicationRepo(TenantApplications.create(componentRegistry, new MockReloadHandler(), tenantName));
         tenantRepository.addTenant(tenantBuilder);
         return tenantRepository.getTenant(tenantName);
     }