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From "Scott Chen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1608) Allow users to do speculative execution of a task manually
Date Tue, 16 Nov 2010 22:05:21 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12932675#action_12932675
] 

Scott Chen commented on MAPREDUCE-1608:
---------------------------------------

Hi Arun,
bq. How do you prevent devious/malicious users from speculating on all their tasks via a simple
shell script?
Currently if a user wants to do that, the user can achieve this by setting
{code}
 mapreduce.job.speculative.slowtaskthreshold = 0
{code}
This way is even simpler.

> Allow users to do speculative execution of a task manually
> ----------------------------------------------------------
>
>                 Key: MAPREDUCE-1608
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1608
>             Project: Hadoop Map/Reduce
>          Issue Type: New Feature
>            Reporter: Scott Chen
>            Assignee: Scott Chen
>
> Speculative execution improves the latency of the job. Sometimes the job has few very
slow reducers. Spending a little more resource on speculative tasks can improve the latency
a lot. It will be nice that the users can manually select one task and force the speculative
execution on that task just like we can manually kill/fail task.
> The proposal is add link says "speculate" in taskdetails.jsp page where we do "kill/fail".
> Thoughts? 

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