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From "Vinod Kumar Vavilapalli (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-4813) AM timing out during job commit
Date Tue, 27 Nov 2012 02:06:58 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4813?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13504304#comment-13504304

Vinod Kumar Vavilapalli commented on MAPREDUCE-4813:

Started looking at the patch but realized a thing. When we fix MAPREDUCE-4815, commitJob won't
be expensive anymore? We still need to make sure that a hung DFS move doesn't make the AM
timeout, but I believe that is automatically handled via RPC timeouts for e.g.
> AM timing out during job commit
> -------------------------------
>                 Key: MAPREDUCE-4813
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4813
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: applicationmaster
>    Affects Versions: 0.23.3, 2.0.1-alpha
>            Reporter: Jason Lowe
>            Assignee: Jason Lowe
>            Priority: Critical
>         Attachments: MAPREDUCE-4813.patch
> The AM calls the output committer's {{commitJob}} method synchronously during JobImpl
state transitions, which means the JobImpl write lock is held the entire time the job is being
committed.  Holding the write lock prevents the RM allocator thread from heartbeating to the
RM.  Therefore if committing the job takes too long (e.g.: the job has tons of files to commit
and/or the namenode is bogged down) then the AM appears to be unresponsive to the RM and the
RM kills the AM attempt.

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