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https://issues.apache.org/jira/browse/MAPREDUCE-5583?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14344331#comment-14344331
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Junping Du commented on MAPREDUCE-5583:
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bq. As that task completes the ask will go from 0 to 1 since we can now run
another task. In that case oldReqLimit.getNumContainers == 0 and
newReqLimit.getNumContainers() == 1, so they are not the same.
I see. I always forgot our old hacking that compare() in
ResourceRequestComparator is inconsistent with equals() in ResourceRequest. :(
Latest patch LGTM. Given latest patch is upload almost 1 week ago, kick off
Jenkins test again.
+1 pending on Jenkins result.
> Ability to limit running map and reduce tasks
> ---------------------------------------------
>
> Key: MAPREDUCE-5583
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5583
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: mr-am, mrv2
> Affects Versions: 0.23.9, 2.1.1-beta
> Reporter: Jason Lowe
> Assignee: Jason Lowe
> Attachments: MAPREDUCE-5583-branch2.4.1.patch,
> MAPREDUCE-5583v1.patch, MAPREDUCE-5583v2.patch, MAPREDUCE-5583v3.patch,
> MAPREDUCE-5583v4.patch
>
>
> It would be nice if users could specify a limit to the number of map or
> reduce tasks that are running simultaneously. Occasionally users are
> performing operations in tasks that can lead to DDoS scenarios if too many
> tasks run simultaneously (e.g.: accessing a database, web service, etc.).
> Having the ability to throttle the number of tasks simultaneously running
> would provide users a way to mitigate issues with too many tasks on a large
> cluster attempting to access a serivce at any one time.
> This is similar to the functionality requested by MAPREDUCE-224 and
> implemented by HADOOP-3412 but was dropped in mrv2.
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