[GitHub] [helix] zhangmeng916 commented on a change in pull request #1460: Allow Stale Reply Messages to Pass without Exceptions

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

zhangmeng916 commented on a change in pull request #1460:
URL: https://github.com/apache/helix/pull/1460#discussion_r504121634



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File path: helix-core/src/main/java/org/apache/helix/messaging/handling/AsyncCallbackService.java
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@@ -113,12 +104,19 @@ public HelixTaskResult handleMessage() throws InterruptedException {
           + _correlationId);
 
       AsyncCallback callback = _callbackMap.get(_correlationId);
-      synchronized (callback) {
-        callback.onReply(_message);
-        if (callback.isDone()) {
-          _logger.info("Removing finished callback, correlationid:" + _correlationId);
-          _callbackMap.remove(_correlationId);
+      if (callback != null) {
+        synchronized (callback) {
+          callback.onReply(_message);
+          if (callback.isDone()) {
+            _logger.info("Removing finished callback, correlationid:" + _correlationId);
+            _callbackMap.remove(_correlationId);
+          }
         }
+      } else {
+        String msg = "Message " + _message.getMsgId()
+            + " does not have correponding callback. Probably timed out already. Correlation id: "
+            + _correlationId;
+        _logger.warn(msg);

Review comment:
       A question regarding the description, if the error is just logged here, meaning the users won't really know there is a mismatch. If the callback is not done, they won't be able to distinguish between this error and other errors. Is this the expected behavior?




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