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