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https://issues.apache.org/jira/browse/MAPREDUCE-2705?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13073805#comment-13073805
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Thomas Graves commented on MAPREDUCE-2705:
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when I first submitted the patch the tests on trunk were already broken. For
instance see
https://builds.apache.org/view/G-L/view/Hadoop/job/PreCommit-MAPREDUCE-Build/472/
which is for a different jira. Let me rerun now just to double check and I'll
update you on results.
> tasks localized and launched serially by TaskLauncher - causing other tasks
> to be delayed
> -----------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-2705
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2705
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: tasktracker
> Affects Versions: 0.20.205.0
> Reporter: Thomas Graves
> Assignee: Thomas Graves
> Fix For: 0.20.205.0, 0.23.0
>
> Attachments: MAPREDUCE-2705-branch20.patch, MAPREDUCE-2705-trunk.patch
>
>
> The current TaskLauncher serially launches new tasks one at a time. During
> the launch it does the localization and then starts the map/reduce task.
> This can cause any other tasks to be blocked waiting for the current task to
> be localized and started. In some instances we have seen a task that has a
> large file to localize (1.2MB) block another task for about 40 minutes. This
> particular task being blocked was a cleanup task which caused the job to be
> delayed finishing for the 40 minutes.
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