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Posted to mapreduce-issues@hadoop.apache.org by "Mingzhe Hao (JIRA)" <ji...@apache.org> on 2014/04/28 04:02:14 UTC

[jira] [Commented] (MAPREDUCE-5863) Killing task attempts while speculation is enabled can cause the job to fail

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5863?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13982705#comment-13982705 ] 

Mingzhe Hao commented on MAPREDUCE-5863:
----------------------------------------

instead of being killed, the succeeded TA can also fail to change the task into SCHEDULED state

> Killing task attempts while speculation is enabled can cause the job to fail
> ----------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-5863
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5863
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>    Affects Versions: 2.4.0
>            Reporter: Mingzhe Hao
>
> There could be a race condition when a T_ADD_SPEC_ATTEMPT is being fired, the task gets succeeded and then killed by the client. In that case, the task state changes from SUCCEEDED to SCHEDULED, and then task gets a T_ADD_SPEC_ATTEMPT event, which is invalid for SCHEDULED state.
> 1. Task is running.
> 2. Speculator fires a T_ADD_SPEC_ATTEMPT
> 3. Before task receives T_ADD_SPEC_ATTEMPT, it succeeds
> 4. Succeeded TA receives TA_KILL from client. Now the task is at SCHEDULED state.
> 5. Task receives T_ADD_SPEC_ATTEMPT, since this is an unexpected event, the job fails.



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