[jira] Updated: (MAPREDUCE-873) Simplify Job Recovery

["Sharad Agarwal (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MAPREDUCE-873?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sharad Agarwal updated MAPREDUCE-873:
-------------------------------------

      Resolution: Fixed
    Release Note: 
Simplifies job recovery. On jobtracker restart, incomplete jobs are resubmitted and all tasks reexecute.
This JIRA removes a public constructor in JobInProgress.
    Hadoop Flags: [Incompatible change, Reviewed]  (was: [Incompatible change])
          Status: Resolved  (was: Patch Available)

I just committed this.

> 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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