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From "Allen Wittenauer (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (MAPREDUCE-155) Each task tracker should not execute more than one speculative task
Date Thu, 17 Jul 2014 18:25:08 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-155?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Allen Wittenauer resolved MAPREDUCE-155.
----------------------------------------

    Resolution: Incomplete

Closing this as stale since spec exec has undergone quite a bit of overhauling which I'm confident
included fixing this... at least, I've never seen a job get multiple versions of the same
task assigned to the same node in practice.

> Each task tracker should not execute more than one speculative task
> -------------------------------------------------------------------
>
>                 Key: MAPREDUCE-155
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-155
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>            Reporter: Runping Qi
>
> I noticed that sometimes, a tasktracker started 2 or three speculative mapper tasks.
> That seems counter productive. You want to speculative execution complete as soon as
possible.
> Thus, it is better to spread speculative execution over multiple trackers. A simple way
to 
> achieve that is to limit the number of speculative eecution concurrently.



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