YARN-4398. Remove unnecessary synchronization in RMStateStore. Contributed by Ning Ding

hadoop-yarn-project/CHANGES.txt

@@ -1121,6 +1121,8 @@ Release 2.7.3 - UNRELEASED
     YARN-4380. TestResourceLocalizationService.testDownloadingResourcesOnContainerKill
     fails intermittently. (Varun Saxena via ozawa)
 
+    YARN-4398. Remove unnecessary synchronization in RMStateStore. (Ning Ding via jianhe)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/event/AsyncDispatcher.java

@@ -64,7 +64,7 @@ public class AsyncDispatcher extends AbstractService implements Dispatcher {
   // For drainEventsOnStop enabled only, block newly coming events into the
   // queue while stopping.
   private volatile boolean blockNewEvents = false;
-  private EventHandler handlerInstance = null;
+  private final EventHandler handlerInstance = new GenericEventHandler();
 
   private Thread eventHandlingThread;
   protected final Map<Class<? extends Enum>, EventHandler> eventDispatchers;
@@ -224,9 +224,6 @@ public class AsyncDispatcher extends AbstractService implements Dispatcher {
 
   @Override
   public EventHandler getEventHandler() {
-    if (handlerInstance == null) {
-      handlerInstance = new GenericEventHandler();
-    }
     return handlerInstance;
   }
 

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/recovery/RMStateStore.java

@@ -737,7 +737,7 @@ public abstract class RMStateStore extends AbstractService {
    * RMAppStoredEvent will be sent on completion to notify the RMApp
    */
   @SuppressWarnings("unchecked")
-  public synchronized void storeNewApplication(RMApp app) {
+  public void storeNewApplication(RMApp app) {
     ApplicationSubmissionContext context = app
                                             .getApplicationSubmissionContext();
     assert context instanceof ApplicationSubmissionContextPBImpl;
@@ -748,7 +748,7 @@ public abstract class RMStateStore extends AbstractService {
   }
 
   @SuppressWarnings("unchecked")
-  public synchronized void updateApplicationState(
+  public void updateApplicationState(
       ApplicationStateData appState) {
     dispatcher.getEventHandler().handle(new RMStateUpdateAppEvent(appState));
   }
@@ -780,7 +780,7 @@ public abstract class RMStateStore extends AbstractService {
    * This does not block the dispatcher threads
    * RMAppAttemptStoredEvent will be sent on completion to notify the RMAppAttempt
    */
-  public synchronized void storeNewApplicationAttempt(RMAppAttempt appAttempt) {
+  public void storeNewApplicationAttempt(RMAppAttempt appAttempt) {
     Credentials credentials = getCredentialsFromAppAttempt(appAttempt);
 
     AggregateAppResourceUsage resUsage =
@@ -798,7 +798,7 @@ public abstract class RMStateStore extends AbstractService {
   }
 
   @SuppressWarnings("unchecked")
-  public synchronized void updateApplicationAttemptState(
+  public void updateApplicationAttemptState(
       ApplicationAttemptStateData attemptState) {
     dispatcher.getEventHandler().handle(
       new RMStateUpdateAppAttemptEvent(attemptState));
@@ -963,7 +963,7 @@ public abstract class RMStateStore extends AbstractService {
    * There is no notification of completion for this operation.
    */
   @SuppressWarnings("unchecked")
-  public synchronized void removeApplication(RMApp app) {
+  public void removeApplication(RMApp app) {
     ApplicationStateData appState =
         ApplicationStateData.newInstance(app.getSubmitTime(),
             app.getStartTime(), app.getApplicationSubmissionContext(),