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https://issues.apache.org/jira/browse/ZOOKEEPER-2189?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14565932#comment-14565932
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Hudson commented on ZOOKEEPER-2189:
-----------------------------------
FAILURE: Integrated in ZooKeeper-trunk #2707 (See
[https://builds.apache.org/job/ZooKeeper-trunk/2707/])
ZOOKEEPER-2189: QuorumCnxManager: use BufferedOutputStream for initial msg
(Raul Gutierrez Segales via hdeng) (hdeng:
http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1682558)
* /zookeeper/trunk/CHANGES.txt
*
/zookeeper/trunk/src/java/main/org/apache/zookeeper/server/quorum/QuorumCnxManager.java
> multiple leaders can be elected when configs conflict
> -----------------------------------------------------
>
> Key: ZOOKEEPER-2189
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2189
> Project: ZooKeeper
> Issue Type: Bug
> Components: leaderElection
> Affects Versions: 3.5.0
> Reporter: Akihiro Suda
>
> This sequence leads the ensemble to a split-brain state:
> * Start server 1 (config=1:participant, 2:participant, 3:participant)
> * Start server 2 (config=1:participant, 2:participant, 3:participant)
> * 1 and 2 believe 2 is the leader
> * Start server 3 (config=1:observer, 2:observer, 3:participant)
> * 3 believes 3 is the leader, although 1 and 2 still believe 2 is the leader
> Such a split-brain ensemble is very unstable.
> Znodes can be lost easily:
> * Create some znodes on 2
> * Restart 1 and 2
> * 1, 2 and 3 can think 3 is the leader
> * znodes created on 2 are lost, as 1 and 2 sync with 3
> I consider this behavior as a bug and that ZK should fail gracefully if a
> participant is listed as an observer in the config.
> In current implementation, ZK cannot detect such an invalid config, as
> FastLeaderElection.sendNotification() sends notifications to only voting
> members and hence there is no message from observers(1 and 2) to the new
> voter (3).
> I think FastLeaderElection.sendNotification() should send notifications to
> all the members and FastLeaderElection.Messenger.WorkerReceiver.run() should
> verify acks.
> Any thoughts?
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