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https://issues.apache.org/jira/browse/ZOOKEEPER-2746?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15956074#comment-15956074
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ASF GitHub Bot commented on ZOOKEEPER-2746:
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Github user shralex commented on the issue:
https://github.com/apache/zookeeper/pull/213
LGTM
> Leader hand off during dynamic reconfig is a best effort, not a guarantee,
> when none trivial changes happen on current leader.
> ------------------------------------------------------------------------------------------------------------------------------
>
> 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
>
> When none 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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