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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-873) Simplify Job Recovery
Date Tue, 01 Sep 2009 10:49:32 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-873?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12749849#action_12749849

Hudson commented on MAPREDUCE-873:

Integrated in Hadoop-Mapreduce-trunk-Commit #9 (See [http://hudson.zones.apache.org/hudson/job/Hadoop-Mapreduce-trunk-Commit/9/])
    . Moving the CHANGES.txt comment to Incompatible section.
. Simplify job recovery. InComplete jobs are resubmitted on jobtracker restart. Contributed
by Sharad Agarwal.

> Simplify Job Recovery
> ---------------------
>                 Key: MAPREDUCE-873
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-873
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: jobtracker
>    Affects Versions: 0.20.1
>            Reporter: Devaraj Das
>            Assignee: Sharad Agarwal
>             Fix For: 0.21.0
>         Attachments: 873_v1.patch, 873_v2.patch, 873_v3.patch
> On a couple of occasions we have seen the JobTracker not being able to handle job recovery
well, and leading to cluster downtime after a restart. The current design for handling job
recovery is complex and prone to corner cases not being handled well enough. In retrospect,
it seems like the transaction log based approach as was proposed on HADOOP-3245 (http://tinyurl.com/luh9hb),
would have been a better/simpler model. However, that is a big project, and it seems for the
medium term, just handling job re-submissions after a restart is a good tradeoff. That is,
the JobTracker after getting restarted, will resubmit all jobs that were running in its past
life. They will all start from the beginning (downside is completed tasks will reexecute).
In the long term, the transaction log model or some variant of that should be pursued.
> Thoughts/comments welcome.

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