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Posted to mapreduce-issues@hadoop.apache.org by "Allen Wittenauer (JIRA)" <ji...@apache.org> on 2014/07/17 20:25:08 UTC

[jira] [Resolved] (MAPREDUCE-155) Each task tracker should not execute more than one speculative task

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

Allen Wittenauer resolved MAPREDUCE-155.
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    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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