diff --git a/Documentation/dev-bazel.txt b/Documentation/dev-bazel.txt
index a6f8f5f7de..ef1279aa1b 100644
--- a/Documentation/dev-bazel.txt
+++ b/Documentation/dev-bazel.txt
@@ -3,7 +3,7 @@
 [[installation]]
 == Installation
 
-You need to use Java 8 and Node.js for building gerrit.
+You need to use Python 2, Java 8, and Node.js for building gerrit.
 
 You can install Bazel from the bazel.io:
 https://www.bazel.io/versions/master/docs/install.html
diff --git a/gerrit-pgm/src/main/java/com/google/gerrit/pgm/util/BatchProgramModule.java b/gerrit-pgm/src/main/java/com/google/gerrit/pgm/util/BatchProgramModule.java
index 9e5723d461..918da61a67 100644
--- a/gerrit-pgm/src/main/java/com/google/gerrit/pgm/util/BatchProgramModule.java
+++ b/gerrit-pgm/src/main/java/com/google/gerrit/pgm/util/BatchProgramModule.java
@@ -52,7 +52,9 @@ import com.google.gerrit.server.config.DisableReverseDnsLookupProvider;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.config.GitReceivePackGroups;
 import com.google.gerrit.server.config.GitUploadPackGroups;
+import com.google.gerrit.server.extensions.events.EventUtil;
 import com.google.gerrit.server.extensions.events.GitReferenceUpdated;
+import com.google.gerrit.server.extensions.events.RevisionCreated;
 import com.google.gerrit.server.git.MergeUtil;
 import com.google.gerrit.server.git.SearchingChangeCacheImpl;
 import com.google.gerrit.server.git.TagCache;
@@ -172,7 +174,9 @@ public class BatchProgramModule extends FactoryModule {
     factory(SubmitRuleEvaluator.Factory.class);
 
     bind(ChangeJson.Factory.class).toProvider(Providers.<ChangeJson.Factory>of(null));
-    bind(AccountVisibility.class).toProvider(AccountVisibilityProvider.class).in(SINGLETON);
+    bind(EventUtil.class).toProvider(Providers.<EventUtil>of(null));
     bind(GitReferenceUpdated.class).toInstance(GitReferenceUpdated.DISABLED);
+    bind(RevisionCreated.class).toInstance(RevisionCreated.DISABLED);
+    bind(AccountVisibility.class).toProvider(AccountVisibilityProvider.class).in(SINGLETON);
   }
 }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/AgreementSignup.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/AgreementSignup.java
index 669690af28..45f1159eca 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/AgreementSignup.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/AgreementSignup.java
@@ -19,7 +19,9 @@ import com.google.gerrit.extensions.events.AgreementSignupListener;
 import com.google.gerrit.extensions.registration.DynamicSet;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 
+@Singleton
 public class AgreementSignup {
   private final DynamicSet<AgreementSignupListener> listeners;
   private final EventUtil util;
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/AssigneeChanged.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/AssigneeChanged.java
index 2583744a30..8f8f13ed22 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/AssigneeChanged.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/AssigneeChanged.java
@@ -23,10 +23,12 @@ import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.sql.Timestamp;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class AssigneeChanged {
   private static final Logger log = LoggerFactory.getLogger(AssigneeChanged.class);
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeAbandoned.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeAbandoned.java
index ef6961606c..8b8522ac5e 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeAbandoned.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeAbandoned.java
@@ -29,11 +29,13 @@ import com.google.gerrit.server.patch.PatchListObjectTooLargeException;
 import com.google.gerrit.server.permissions.PermissionBackendException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.io.IOException;
 import java.sql.Timestamp;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class ChangeAbandoned {
   private static final Logger log = LoggerFactory.getLogger(ChangeAbandoned.class);
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeMerged.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeMerged.java
index e9ae356046..217e5d67c2 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeMerged.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeMerged.java
@@ -29,11 +29,13 @@ import com.google.gerrit.server.patch.PatchListObjectTooLargeException;
 import com.google.gerrit.server.permissions.PermissionBackendException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.io.IOException;
 import java.sql.Timestamp;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class ChangeMerged {
   private static final Logger log = LoggerFactory.getLogger(ChangeMerged.class);
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeRestored.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeRestored.java
index c25deab366..6715467569 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeRestored.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeRestored.java
@@ -29,11 +29,13 @@ import com.google.gerrit.server.patch.PatchListObjectTooLargeException;
 import com.google.gerrit.server.permissions.PermissionBackendException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.io.IOException;
 import java.sql.Timestamp;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class ChangeRestored {
   private static final Logger log = LoggerFactory.getLogger(ChangeRestored.class);
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeReverted.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeReverted.java
index e57cbdd0cf..1e91ab3cc4 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeReverted.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ChangeReverted.java
@@ -21,10 +21,12 @@ import com.google.gerrit.extensions.registration.DynamicSet;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.sql.Timestamp;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class ChangeReverted {
   private static final Logger log = LoggerFactory.getLogger(ChangeReverted.class);
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/CommentAdded.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/CommentAdded.java
index 77cd1a8ef3..03ad58c3d7 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/CommentAdded.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/CommentAdded.java
@@ -30,12 +30,14 @@ import com.google.gerrit.server.patch.PatchListObjectTooLargeException;
 import com.google.gerrit.server.permissions.PermissionBackendException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.io.IOException;
 import java.sql.Timestamp;
 import java.util.Map;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class CommentAdded {
   private static final Logger log = LoggerFactory.getLogger(CommentAdded.class);
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/EventUtil.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/EventUtil.java
index 95d7132749..8feeee0e6b 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/EventUtil.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/EventUtil.java
@@ -34,6 +34,7 @@ import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
+import com.google.inject.Singleton;
 import java.io.IOException;
 import java.sql.Timestamp;
 import java.util.EnumSet;
@@ -42,6 +43,7 @@ import java.util.Map;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class EventUtil {
   private static final Logger log = LoggerFactory.getLogger(EventUtil.class);
 
@@ -64,7 +66,7 @@ public class EventUtil {
 
   private final ChangeData.Factory changeDataFactory;
   private final Provider<ReviewDb> db;
-  private final ChangeJson changeJson;
+  private final ChangeJson.Factory changeJsonFactory;
 
   @Inject
   EventUtil(
@@ -73,11 +75,11 @@ public class EventUtil {
       Provider<ReviewDb> db) {
     this.changeDataFactory = changeDataFactory;
     this.db = db;
-    this.changeJson = changeJsonFactory.create(CHANGE_OPTIONS);
+    this.changeJsonFactory = changeJsonFactory;
   }
 
   public ChangeInfo changeInfo(Change change) throws OrmException {
-    return changeJson.format(change);
+    return changeJsonFactory.create(CHANGE_OPTIONS).format(change);
   }
 
   public RevisionInfo revisionInfo(Project project, PatchSet ps)
@@ -90,7 +92,7 @@ public class EventUtil {
       throws OrmException, PatchListNotAvailableException, GpgException, IOException,
           PermissionBackendException {
     ChangeData cd = changeDataFactory.create(db.get(), project, ps.getId().getParentKey());
-    return changeJson.getRevisionInfo(cd, ps);
+    return changeJsonFactory.create(CHANGE_OPTIONS).getRevisionInfo(cd, ps);
   }
 
   public AccountInfo accountInfo(Account a) {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/GitReferenceUpdated.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/GitReferenceUpdated.java
index 2b65965c0b..be14827e4a 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/GitReferenceUpdated.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/GitReferenceUpdated.java
@@ -21,11 +21,13 @@ import com.google.gerrit.extensions.registration.DynamicSet;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import org.eclipse.jgit.lib.BatchRefUpdate;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.RefUpdate;
 import org.eclipse.jgit.transport.ReceiveCommand;
 
+@Singleton
 public class GitReferenceUpdated {
   public static final GitReferenceUpdated DISABLED =
       new GitReferenceUpdated() {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/HashtagsEdited.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/HashtagsEdited.java
index b086beba75..1c4b43cf91 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/HashtagsEdited.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/HashtagsEdited.java
@@ -24,12 +24,14 @@ import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.sql.Timestamp;
 import java.util.Collection;
 import java.util.Set;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class HashtagsEdited {
   private static final Logger log = LoggerFactory.getLogger(HashtagsEdited.class);
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/PluginEvent.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/PluginEvent.java
index bd643e2020..8680ab1528 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/PluginEvent.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/PluginEvent.java
@@ -17,7 +17,9 @@ package com.google.gerrit.server.extensions.events;
 import com.google.gerrit.extensions.events.PluginEventListener;
 import com.google.gerrit.extensions.registration.DynamicSet;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 
+@Singleton
 public class PluginEvent {
   private final DynamicSet<PluginEventListener> listeners;
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ReviewerAdded.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ReviewerAdded.java
index fc6881dfea..6ffdd02d84 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ReviewerAdded.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ReviewerAdded.java
@@ -30,12 +30,14 @@ import com.google.gerrit.server.patch.PatchListObjectTooLargeException;
 import com.google.gerrit.server.permissions.PermissionBackendException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.io.IOException;
 import java.sql.Timestamp;
 import java.util.List;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class ReviewerAdded {
   private static final Logger log = LoggerFactory.getLogger(ReviewerAdded.class);
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ReviewerDeleted.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ReviewerDeleted.java
index 28e07a96e7..1d00a50527 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ReviewerDeleted.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/ReviewerDeleted.java
@@ -30,12 +30,14 @@ import com.google.gerrit.server.patch.PatchListObjectTooLargeException;
 import com.google.gerrit.server.permissions.PermissionBackendException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.io.IOException;
 import java.sql.Timestamp;
 import java.util.Map;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class ReviewerDeleted {
   private static final Logger log = LoggerFactory.getLogger(ReviewerDeleted.class);
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/RevisionCreated.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/RevisionCreated.java
index 76779caa58..d2ef2d5f81 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/RevisionCreated.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/RevisionCreated.java
@@ -29,14 +29,27 @@ import com.google.gerrit.server.patch.PatchListObjectTooLargeException;
 import com.google.gerrit.server.permissions.PermissionBackendException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.io.IOException;
 import java.sql.Timestamp;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class RevisionCreated {
   private static final Logger log = LoggerFactory.getLogger(RevisionCreated.class);
 
+  public static final RevisionCreated DISABLED =
+      new RevisionCreated() {
+        @Override
+        public void fire(
+            Change change,
+            PatchSet patchSet,
+            Account uploader,
+            Timestamp when,
+            NotifyHandling notify) {}
+      };
+
   private final DynamicSet<RevisionCreatedListener> listeners;
   private final EventUtil util;
 
@@ -46,6 +59,11 @@ public class RevisionCreated {
     this.util = util;
   }
 
+  private RevisionCreated() {
+    this.listeners = null;
+    this.util = null;
+  }
+
   public void fire(
       Change change, PatchSet patchSet, Account uploader, Timestamp when, NotifyHandling notify) {
     if (!listeners.iterator().hasNext()) {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/TopicEdited.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/TopicEdited.java
index d7e7245864..7275ced355 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/TopicEdited.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/TopicEdited.java
@@ -23,10 +23,12 @@ import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.sql.Timestamp;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class TopicEdited {
   private static final Logger log = LoggerFactory.getLogger(TopicEdited.class);
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/VoteDeleted.java b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/VoteDeleted.java
index 8944698f76..c377bdc54e 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/VoteDeleted.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/extensions/events/VoteDeleted.java
@@ -30,12 +30,14 @@ import com.google.gerrit.server.patch.PatchListObjectTooLargeException;
 import com.google.gerrit.server.permissions.PermissionBackendException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.io.IOException;
 import java.sql.Timestamp;
 import java.util.Map;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+@Singleton
 public class VoteDeleted {
   private static final Logger log = LoggerFactory.getLogger(VoteDeleted.class);