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From "Robert Joseph Evans (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-5079) Recovery should restore task state from job history info directly
Date Wed, 20 Mar 2013 14:49:16 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5079?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13607665#comment-13607665
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Robert Joseph Evans commented on MAPREDUCE-5079:
------------------------------------------------

I like the approach too +1 for the idea.  I looked at the code and I only have one minor comment
about the code itself.

in JobStartEvent.java {code}long recoveredJobStartTime;{code} is not marked as private.

My Biggest concern is with the testing. Like you pointed out that it needs more unit tests,
especially to cover some of the issues where job recovery hangs that the previous implementation
did not cover.  But also have you done some actual tests on real clusters?  Have you run the
complete set of MR tests, because the precommit only ran a small subset of the tests.

                
> Recovery should restore task state from job history info directly
> -----------------------------------------------------------------
>
>                 Key: MAPREDUCE-5079
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5079
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: mr-am
>    Affects Versions: 0.23.7
>            Reporter: Jason Lowe
>            Assignee: Jason Lowe
>         Attachments: MAPREDUCE-5079.patch
>
>
> We've encountered a lot of hanging issues during MR-AM recovery because the state machines
don't always end up in the same states after recovery.  This is especially true when speculative
execution is enabled.  It should be straightforward to restore task and task attempt states
directly from the TaskInfo and TaskAttemptInfo records in the job history file to avoid relying
on the task state machines ending up in the proper states with the proper number of attempts.
> This should be a more robust solution that would also give us the option of recovering
start time and log locations for tasks that were in-progress when the AM crashed.

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