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From "Bikas Saha (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-1029) Allow embedding leader election into the RM
Date Tue, 17 Dec 2013 04:03:08 GMT

    [ https://issues.apache.org/jira/browse/YARN-1029?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13850087#comment-13850087

Bikas Saha commented on YARN-1029:

I am not sure what additional work is needed in YARN-1177 given that the RM already implements
the HAServiceProtocol. There shouldnt be any since the API needed for ZKFC to manage the RM
are already there. Perhaps we only need some logic in the RM for some additional checks during
automatic failover. So functionally ZKFC supports should already be there. 
This jira was meant to add built-in failover in the RM given that RM already uses ZK store
and to simplify deployments. I think our initial guess was the ZKFC would be simpler to embed
but Karthiks observation after writing some code is that the elector library is simpler to
embed. Lets review the patches to see the merits in the code.
I agree that we dont need to merge the sessions for leader election and storage right now.
They are notionally separate and lets observe a case where one session gets lost but not the
other before trying to merge them together.

> Allow embedding leader election into the RM
> -------------------------------------------
>                 Key: YARN-1029
>                 URL: https://issues.apache.org/jira/browse/YARN-1029
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>            Reporter: Bikas Saha
>            Assignee: Karthik Kambatla
>         Attachments: embedded-zkfc-approach.patch, yarn-1029-0.patch, yarn-1029-0.patch,
> It should be possible to embed common ActiveStandyElector into the RM such that ZooKeeper
based leader election and notification is in-built. In conjunction with a ZK state store,
this configuration will be a simple deployment option.

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