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Date: Fri, 30 Nov 2012 11:49:59 +0000 (UTC)
From: "Sharad Agarwal (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
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Subject: [jira] [Commented] (MAPREDUCE-4832) MR AM can get in a split brain
 situation
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-4832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13507281#comment-13507281 ] 

Sharad Agarwal commented on MAPREDUCE-4832:
-------------------------------------------

MAPREDUCE-2702 introduced a job level commit. Task commit from competing AMs should not overstep each other.

Job level commit should ensure only the first one succeeds. Are you observing this in the cluster ?
                
> MR AM can get in a split brain situation
> ----------------------------------------
>
>                 Key: MAPREDUCE-4832
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4832
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: applicationmaster
>    Affects Versions: 2.0.2-alpha, 0.23.5
>            Reporter: Robert Joseph Evans
>            Priority: Critical
>
> It is possible for a networking issue to happen where the RM thinks an AM has gone down and launches a replacement, but the previous AM is still up and running.  If the previous AM does not need any more resources from the RM it could try to commit either tasks or jobs.  This could cause lots of problems where the second AM finishes and tries to commit too.  This could result in data corruption.  

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