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From "Jason Lowe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-4813) AM timing out during job commit
Date Tue, 27 Nov 2012 14:27:59 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4813?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13504635#comment-13504635
] 

Jason Lowe commented on MAPREDUCE-4813:
---------------------------------------

MAPREDUCE-4815 only addresses FileOutputCommitter and friends, but the committer is arbitrary
user code.  It could be doing all sorts of things including connecting to databases, etc.
 So I still think we need this, although the priority of it is reduced given how many things
are built from FileOutputCommitter.
                
> 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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