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From "Amar Kamat (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3632) Fix speculative execution or allow premature stop
Date Wed, 25 Jun 2008 05:16:47 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3632?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12607860#action_12607860

Amar Kamat commented on HADOOP-3632:

One crude way of doing this would be to set the _{{mapred.max.map.failures.percent}}_ to something
like 1% and then kill all the attempts that are stragglers using _{{JobTracker.killTask()}}_.
 You should kill atleast _{{mapred.map.max.attempts}}_ to get the TIP killed.  One thing that
can be added in the framework would be the facility to kill a TIP.

> Fix speculative execution or allow premature stop
> -------------------------------------------------
>                 Key: HADOOP-3632
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3632
>             Project: Hadoop Core
>          Issue Type: New Feature
>    Affects Versions: 0.16.3
>            Reporter: Severin Hacker
>   Original Estimate: 72h
>  Remaining Estimate: 72h
> I run 50 iterations of a program with 500 maps and no reduces. I have noticed the following
> In 50% of the iterations:
> 499 maps finish in 50 seconds
> 1 map finishes after 4 minutes
> Total time is 4 minutes.
> In 50% of the iterations:
> 500 maps finish in 50 seconds
> Total time is 50 seconds.
> It would be nice if I could tell hadoop to stop after 99% of the maps have finished (and
not wait for that last straggler). In my application it's perfectly fine if I only get 99%
of the results, as long as the straggler is not always using the same data.
> Please fix!

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