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https://issues.apache.org/jira/browse/HADOOP-8217?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13240171#comment-13240171
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Suresh Srinivas commented on HADOOP-8217:
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Todd, I think this has been brought up in other comments as well. I am very
uncomfortable with just creating jiras for each scenarios as we think of,
instead of capturing it in a design document. I cannot keep up with jiras, that
are created and committed in short periods of time. I do not want to comment on
jiras asking for time and impede progress. A design document helps here.
Perhaps, we should setup a meeting to go over the design, and discuss issues in
more detail.
> Edge case split-brain race in ZK-based auto-failover
> ----------------------------------------------------
>
> Key: HADOOP-8217
> URL: https://issues.apache.org/jira/browse/HADOOP-8217
> Project: Hadoop Common
> Issue Type: Bug
> Components: ha
> Affects Versions: 0.24.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
>
> As discussed in HADOOP-8206, the current design for automatic failover has
> the following race:
> - ZKFC1 gets active lock
> - ZKFC1 is about to send transitionToActive() and machine freezes (eg GC
> pause + swapping)
> - ZKFC1 loses its ZK lock, ZKFC2 gets ZK lock
> - ZKFC2 calls transitionToStandby on NN1, and transitions NN2 to active
> - ZKFC1 wakes up from pause, calls transitionToActive(), now we have a bad
> situation
> This is rare, since it requires ZKFC1 to freeze longer than its ZK session
> timeout, but worth fixing, since the results can be disastrous.
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