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From "Jian He (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-1210) During RM restart, RM should start a new attempt only when previous attempt exits for real
Date Wed, 18 Sep 2013 05:41:52 GMT

    [ https://issues.apache.org/jira/browse/YARN-1210?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13770457#comment-13770457
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Jian He commented on YARN-1210:
-------------------------------

Nowadays on NM resync with RM, all containers including AM is killed before NM can reregister
with RM. So the 1st AM should be guaranteed to exit before the 2nd AM is launched as long
as they are running on the same machine. If the 2nd AM is running on a different machine from
the 1st AM, we may still see 2 AMs running though.

                
> During RM restart, RM should start a new attempt only when previous attempt exits for
real
> ------------------------------------------------------------------------------------------
>
>                 Key: YARN-1210
>                 URL: https://issues.apache.org/jira/browse/YARN-1210
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>            Reporter: Vinod Kumar Vavilapalli
>            Assignee: Vinod Kumar Vavilapalli
>
> When RM recovers, it can wait for existing AMs to contact RM back and then kill them
forcefully before even starting a new AM. Worst case, RM will start a new AppAttempt after
waiting for 10 mins ( the expiry interval). This way we'll minimize multiple AMs racing with
each other. This can help issues with downstream components like Pig, Hive and Oozie during
RM restart.
> In the mean while, new apps will proceed as usual as existing apps wait for recovery.
> This can continue to be useful after work-preserving restart, so that AMs which can properly
sync back up with RM can continue to run and those that don't are guaranteed to be killed
before starting a new attempt.

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