[jira] [Commented] (MAPREDUCE-4813) AM timing out during job commit

["Vinod Kumar Vavilapalli (JIRA)" <ji...@apache.org>]

    [ 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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