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From "Zhang Zhaoning (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-718) Support for per-phase speculative execution
Date Fri, 16 Oct 2009 01:52:31 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12766370#action_12766370
] 

Zhang Zhaoning commented on MAPREDUCE-718:
------------------------------------------

I think we can incorporate MAPREDUCE-211 with the Health Status for the node anticipated finish
time of the  speculative execution.

> Support for per-phase speculative execution
> -------------------------------------------
>
>                 Key: MAPREDUCE-718
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-718
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: jobtracker
>    Affects Versions: 0.21.0
>            Reporter: Devaraj Das
>             Fix For: 0.21.0
>
>
> It would be good to have support for per-phase speculative execution where the algorithm
looks at the current phase of a task, and compares with the other tasks in the same phase
before deciding to launch a speculative task. That would have the following benefits:
> 1) Support for jobs where map tasks progresses jumps from 0% to 100%. This is true for
some jobs like randomwriter. Today, we would launch speculative tasks for such jobs (assuming
that the tasks are not making progress). But most of them would be unnecessary. 
> 2) In reality, for reduces, the three phases are quite different from each other, and
they take different times too. We should see better results when we look at per-phase speculation.

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