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From "Jason Lowe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-4982) AM hung with one pending map task
Date Fri, 08 Feb 2013 14:37:12 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4982?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13574513#comment-13574513
] 

Jason Lowe commented on MAPREDUCE-4982:
---------------------------------------

bq. Think this could happen if there's no node or rack-local tasks for a container. The assignToMap
in branch-0.23 then falls back to pulling an attempt from 'maps' - which could be a previously
failed attempt.

I initially thought that as well, but given that the {{maps}} field is a {{LinkedHashMap}}
I thought traversal would be in the order they were added to the map.  If that's that case,
I'm not sure how a failed attempt for one map task got ahead of the initial attempt of another
map task.
                
> AM hung with one pending map task
> ---------------------------------
>
>                 Key: MAPREDUCE-4982
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4982
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mr-am
>    Affects Versions: 0.23.6
>            Reporter: Jason Lowe
>
> Saw a job that hung with one pending map task that never ran.  The task was in the SCHEDULED
state with a single attempt that was in the UNASSIGNED state.  The AM looked like it was waiting
for a container from the RM, but the RM was never granting it the one container it needed.
> I suspect the AM botched the container request bookkeeping somehow.  More details to
follow.

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