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From "Flavio Junqueira (JIRA)" <j...@apache.org>
Subject [jira] Commented: (ZOOKEEPER-917) Leader election selected incorrect leader
Date Wed, 03 Nov 2010 17:28:26 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-917?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12927908#action_12927908
] 

Flavio Junqueira commented on ZOOKEEPER-917:
--------------------------------------------

I downloaded your logs, but the out files are empty and I couldn't find the notification messages.
By looking at the excerpts you posted, it sounds like node 1 tells 0 that it is following
2 and node says that it is following (this is fine as node 2 might have received some old
messages), so node 0 must follow 2. Now the question is why node 1 decided to follow 2, specially
because it has a higher zxid and the follower code should have rejected an attempt to follow
a leader from an earlier epoch. 

It would be nice to have a look at the output of node 1. 

> Leader election selected incorrect leader
> -----------------------------------------
>
>                 Key: ZOOKEEPER-917
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-917
>             Project: Zookeeper
>          Issue Type: Bug
>          Components: leaderElection, server
>    Affects Versions: 3.2.2
>         Environment: Cloudera distribution of zookeeper (patched to never cache DNS entries)
> Debian lenny
>            Reporter: Alexandre Hardy
>            Priority: Critical
>             Fix For: 3.3.3, 3.4.0
>
>         Attachments: zklogs-20101102144159SAST.tar.gz
>
>
> We had three nodes running zookeeper:
>   * 192.168.130.10
>   * 192.168.130.11
>   * 192.168.130.14
> 192.168.130.11 failed, and was replaced by a new node 192.168.130.13 (automated startup).
The new node had not participated in any zookeeper quorum previously. The node 192.148.130.11
was permanently removed from service and could not contribute to the quorum any further (powered
off).
> DNS entries were updated for the new node to allow all the zookeeper servers to find
the new node.
> The new node 192.168.130.13 was selected as the LEADER, despite the fact that it had
not seen the latest zxid.
> This particular problem has not been verified with later versions of zookeeper, and no
attempt has been made to reproduce this problem as yet.

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