[GitHub] [helix] dasahcc commented on a change in pull request #1489: Refine the HelixTaskExecutor to reduce duplicate code and clarify the code structure.

[GitBox <gi...@apache.org>]

dasahcc commented on a change in pull request #1489:
URL: https://github.com/apache/helix/pull/1489#discussion_r513783040



##########
File path: helix-core/src/main/java/org/apache/helix/messaging/handling/HelixTaskExecutor.java
##########
@@ -192,43 +191,38 @@ public void registerMessageHandlerFactory(String type, MessageHandlerFactory fac
   @Override
   public void registerMessageHandlerFactory(String type, MessageHandlerFactory factory,
       int threadpoolSize) {
-    if (factory instanceof  MultiTypeMessageHandlerFactory) {
+    if (factory instanceof MultiTypeMessageHandlerFactory) {
       if (!((MultiTypeMessageHandlerFactory) factory).getMessageTypes().contains(type)) {
         throw new HelixException("Message factory type mismatch. Type: " + type + ", factory: "
             + ((MultiTypeMessageHandlerFactory) factory).getMessageTypes());
       }
     } else {
       if (!factory.getMessageType().equals(type)) {
         throw new HelixException(
-            "Message factory type mismatch. Type: " + type + ", factory: " + factory.getMessageType());
+            "Message factory type mismatch. Type: " + type + ", factory: " + factory
+                .getMessageType());
       }
     }
 
     _isShuttingDown = false;
 
-    MsgHandlerFactoryRegistryItem newItem = new MsgHandlerFactoryRegistryItem(factory, threadpoolSize);
+    MsgHandlerFactoryRegistryItem newItem =
+        new MsgHandlerFactoryRegistryItem(factory, threadpoolSize);
     MsgHandlerFactoryRegistryItem prevItem = _hdlrFtyRegistry.putIfAbsent(type, newItem);
     if (prevItem == null) {
-      ExecutorService newPool = Executors.newFixedThreadPool(threadpoolSize, new ThreadFactory() {
-        @Override public Thread newThread(Runnable r) {
-          return new Thread(r, "HelixTaskExecutor-message_handle_thread_" + thread_uid.getAndIncrement());
-        }
-      });
-      ExecutorService prevExecutor = _executorMap.putIfAbsent(type, newPool);
-      if (prevExecutor != null) {
-        LOG.warn("Skip creating a new thread pool for type: " + type + ", already existing pool: "
-            + prevExecutor + ", isShutdown: " + prevExecutor.isShutdown());
-        newPool.shutdown();
-        newPool = null;
-      } else {
+      _executorMap.computeIfAbsent(type, msgType -> {

Review comment:
       We can use putIfAbsent since we are not using the return value anymore here.

##########
File path: helix-core/src/main/java/org/apache/helix/messaging/handling/HelixTaskExecutor.java
##########
@@ -997,30 +873,186 @@ public void onMessage(String instanceName, List<Message> messages,
       }
     }
 
-    // update message state to READ in batch and schedule all read messages
+    // update message state to READ in batch and schedule tasks for all read messages
     if (readMsgs.size() > 0) {
       updateMessageState(readMsgs, accessor, instanceName);
 
-      // Remove message if schedule tasks are failed.
       for (Map.Entry<String, MessageHandler> handlerEntry : stateTransitionHandlers.entrySet()) {
         MessageHandler handler = handlerEntry.getValue();
         NotificationContext context = stateTransitionContexts.get(handlerEntry.getKey());
-        Message msg = handler._message;
-        if (!scheduleTask(new HelixTask(msg, context, handler, this))) {
-          removeMessageFromTaskAndFutureMap(msg);
-          removeMessageFromZK(accessor, msg, instanceName);
-        }
+        scheduleTaskForMessage(instanceName, accessor, handler, context);
       }
 
       for (int i = 0; i < nonStateTransitionHandlers.size(); i++) {
         MessageHandler handler = nonStateTransitionHandlers.get(i);
         NotificationContext context = nonStateTransitionContexts.get(i);
-        Message msg = handler._message;
-        if (!scheduleTask(new HelixTask(msg, context, handler, this))) {
-          removeMessageFromTaskAndFutureMap(msg);
-          removeMessageFromZK(accessor, msg, instanceName);
+        scheduleTaskForMessage(instanceName, accessor, handler, context);
+      }
+    }
+  }
+
+  /**
+   * Inspect the message. Report and remove it if no operation needs to be done.
+   * @param message
+   * @param instanceName
+   * @param changeContext
+   * @param manager
+   * @param sessionId
+   * @param stateTransitionHandlers
+   * @return True if the message is no-op message and no other process step is required.
+   */
+  private boolean checkForNoOpMessage(Message message, String instanceName,

Review comment:
       nit: better to name it as isNoOpMessage? The word check could be confusing here.




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