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https://issues.apache.org/jira/browse/ZOOKEEPER-2746?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15956083#comment-15956083
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Hadoop QA commented on ZOOKEEPER-2746:
--------------------------------------

-1 overall.  GitHub Pull Request  Build
      

    +1 @author.  The patch does not contain any @author tags.

    +1 tests included.  The patch appears to include 3 new or modified tests.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    +1 javac.  The applied patch does not increase the total number of javac 
compiler warnings.

    +1 findbugs.  The patch does not introduce any new Findbugs (version 3.0.1) 
warnings.

    +1 release audit.  The applied patch does not increase the total number of 
release audit warnings.

    -1 core tests.  The patch failed core unit tests.

    +1 contrib tests.  The patch passed contrib unit tests.

Test results: 
https://builds.apache.org/job/PreCommit-ZOOKEEPER-github-pr-build/503//testReport/
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-ZOOKEEPER-github-pr-build/503//artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Console output: 
https://builds.apache.org/job/PreCommit-ZOOKEEPER-github-pr-build/503//console

This message is automatically generated.

> Leader hand-off during dynamic reconfig is best effort, while test always 
> expects it
> ------------------------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-2746
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2746
>             Project: ZooKeeper
>          Issue Type: Test
>    Affects Versions: 3.5.2
>            Reporter: Michael Han
>            Assignee: Michael Han
>             Fix For: 3.6.0
>
>
> When non-trivial config change happens on the leader (e.g. port change, role 
> change) to minimize disruption of quorum we do leader hand off by having the 
> current leader nominate the next leader instead of kicking off a full leader 
> election.
> However this is a best effort and not a guarantee that the new leader of the 
> quorum will be the nominated leader: it is possible that the nominated leader 
> fail to establish the leadership during sync phase, which leads to new 
> election rounds and a different leader elected. 
> In ReconfigTest.testPortChange one check is the new leader after dynamic 
> reconfig of the current leader has to be a different leader; based on what 
> described earlier this is not always the case as the nominated leader might 
> fail to get a quorum to ack its leadership during sync phase, and the old 
> leader might end up as the new leader. We could either fixed the test by 
> removing the check, or always guarantee that the new leader after dynamic 
> reconfig is the nominated leader (which does not make much sense given the 
> nominated leader also has a possibility to crash.).



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