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From "Karthik Kambatla (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-5110) Long task launch delays can lead to multiple parallel attempts of the task
Date Tue, 16 Apr 2013 06:41:17 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5110?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13632626#comment-13632626
] 

Karthik Kambatla commented on MAPREDUCE-5110:
---------------------------------------------

Thanks for chiming in, Vinod.

My intention was precisely to add an aggressive timeout for task attempt launches and keeping
it job-configurable should be good. We can implement it either on JT or TT. Do you think it
is okay to implement in on TT? Please suggest - I ll upload a patch accordingly.

If interested, the user should be able to configure this timeout to be shorter than the tracker-expiry-interval
to ensure a single attempt.

                
> Long task launch delays can lead to multiple parallel attempts of the task
> --------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-5110
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5110
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: tasktracker
>    Affects Versions: 1.1.2
>            Reporter: Karthik Kambatla
>            Assignee: Karthik Kambatla
>         Attachments: expose-mr-5110.patch, mr-5110.patch, mr-5110.patch, mr-5110-tt-only.patch
>
>
> If a task takes too long to launch, the JT expires the task and schedules another attempt.
The earlier attempt can start after the later attempt leading to two parallel attempts running
at the same time. This is particularly an issue if the user turns off speculation and expects
a single attempt of a task to run at any point in time.

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