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https://issues.apache.org/jira/browse/HADOOP-8163?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13236276#comment-13236276
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Todd Lipcon commented on HADOOP-8163:
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bq. So paranoid admin deletes the lock hoping a new master might solve this
If the admin is mucking about in ZK, then all bets are off. The proper thing
for the admin to do is to kill B's failover controller, not to go delete a
znode.
bq. Yes. I am suggesting to do this within the Elector and not at the
ZKFailoverController level. The "self" compare approach would be reasonable as
long as we can assure ourselves that appData will not be same across different
candidates
K, that's the approach in the latest patch I uploaded.
> 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,
> 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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