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https://issues.apache.org/jira/browse/HADOOP-8163?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13236970#comment-13236970
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Todd Lipcon commented on HADOOP-8163:
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bq. In my experience API's once made are hard to change. It would be hard for
someone to change the control flow later once important services like NN HA
depend on the current flow. So punting it for the future would be quite a
distant future indeed
Given this is an internal API, there shouldn't be any resistance to changing it
in the future. It's marked Private/Evolving, meaning that there aren't
guarantees of compatibility to external consumers, and that even for internal
consumers it's likely to change as use cases evolve. I'll file a follow-up JIRA
to consider your recommended API changes, OK?
> 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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