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https://issues.apache.org/jira/browse/HADOOP-8163?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13236116#comment-13236116
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Todd Lipcon commented on HADOOP-8163:
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bq. Am I missing something, or are ensureBaseZNode and baseNodeExists only
called by the tests? If so, we should probably relocate them, or at least mark
them @VisibleForTesting if they can't be moved for some reason.
These are used by my forthcoming patch for the ZK-based automatic failover
controller. The ZKFC has a "-formatZK" flag which calls through to
ensureBaseZNode. Once this gets committed I'll move forward uploading the patch
there.
I fixed the other three of ATM's comments. I'll wait til tomorrow to commit
this in case Bikas has any additional feedback.
> Improve ActiveStandbyElector to provide hooks for fencing old active
> --------------------------------------------------------------------
>
> Key: HADOOP-8163
> URL: https://issues.apache.org/jira/browse/HADOOP-8163
> Project: Hadoop Common
> Issue Type: Improvement
> Components: ha
> Affects Versions: 0.23.3, 0.24.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Attachments: hadoop-8163.txt, hadoop-8163.txt, hadoop-8163.txt
>
>
> When a new node becomes active in an HA setup, it may sometimes have to take
> fencing actions against the node that was formerly active. This JIRA extends
> the ActiveStandbyElector which adds an extra non-ephemeral node into the ZK
> directory, which acts as a second copy of the active node's information.
> Then, if the active loses its ZK session, the next active to be elected may
> easily locate the unfenced node to take the appropriate actions.
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