pkuwm opened a new pull request #1109:
URL: https://github.com/apache/helix/pull/1109


   ### Issues
   
   - [ ] My PR addresses the following Helix issues and references them in the 
PR description:
   
   Fixes #962 
   
   ### Description
   
   - [ ] Here are some details about my PR, including screenshots of any UI 
changes:
   
   For ZkClient's getChildren() operation, if there are a large number of 
children and the response packet size exceeds jute.maxbuffer default value 4MB 
on zk client side, ZkClient will get a ConnectionLossException and keep 
retrying connecting to ZK. The consequence is, the infinite retry may cause 
heavy GC on ZK server and kill ZK server.
   
   We could consider getting number of children in the path and check if it 
exceeds the limit. If it exceeds the children limit, there is no need to retry 
and then exist retry.
   
   The default children limit is set for helix messages length using UUID. 
Packet length of 100K messages doesn't exceed 4 MB.
   
   This change is a workaround to exit retry loop. Once we have a better way to 
solve the problem on ZK server side, we should remove this check.
   
   ### Tests
   
   - [ ] The following tests are written for this issue:
   
   - testGetChildrenOnLargeNumChildren
   
   - [ ] The following is the result of the "mvn test" command on the 
appropriate module:
   
   Running...
   
   ### Commits
   
   - [ ] My commits all reference appropriate Apache Helix GitHub issues in 
their subject lines. In addition, my commits follow the guidelines from "[How 
to write a good git commit message](http://chris.beams.io/posts/git-commit/)":
     1. Subject is separated from body by a blank line
     1. Subject is limited to 50 characters (not including Jira issue reference)
     1. Subject does not end with a period
     1. Subject uses the imperative mood ("add", not "adding")
     1. Body wraps at 72 characters
     1. Body explains "what" and "why", not "how"
   
   ### Documentation (Optional)
   
   - [ ] In case of new functionality, my PR adds documentation in the 
following wiki page:
   
   (Link the GitHub wiki you added)
   
   ### Code Quality
   
   - [ ] My diff has been formatted using helix-style.xml 
   (helix-style-intellij.xml if IntelliJ IDE is used)


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