[GitHub] [helix] kaisun2000 commented on a change in pull request #1344: Reduce unnecessary getChildren call in subscribeForChanges

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

kaisun2000 commented on a change in pull request #1344:
URL: https://github.com/apache/helix/pull/1344#discussion_r483224509



##########
File path: helix-core/src/main/java/org/apache/helix/manager/zk/CallbackHandler.java
##########
@@ -646,10 +645,14 @@ private void subscribeForChanges(NotificationContext.Type callbackType, String p
               break;
             }
             default: {
-              List<String> childNames = _zkClient.getChildren(path);
-              if (childNames != null) {
-                for (String childName : childNames) {
-                  String childPath = path + "/" + childName;
+              // When callback type is FINALIZE, subscribeChildChange doesn't
+              // get children list. We need to read children to unsubscribe data change listeners.
+              if (callbackType == Type.FINALIZE) {
+                children = _zkClient.getChildren(path);
+              }
+              if (children != null) {
+                for (String child : children) {

Review comment:
       Parallel this using Asyc should bring more performance gain, right? why don't we do it here?
   




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