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Date: Tue, 16 Feb 2010 10:29:27 +0000 (UTC)
From: "Amareshwari Sriramadasu (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Updated: (MAPREDUCE-1398) TaskLauncher remains stuck on
 tasks waiting for free nodes even if task is killed.
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     [ https://issues.apache.org/jira/browse/MAPREDUCE-1398?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Amareshwari Sriramadasu updated MAPREDUCE-1398:
-----------------------------------------------

    Attachment: patch-1398-ydist.txt

Patch for Yahoo! distribution. 
Ran ant test and test-patch.  test-patch failed because of MAPREDUCE-1497. All unit tests passed except TestNodeRefresh (due to MAPREDUCE-677). TestNodeRefresh passed when I reran the test.

> TaskLauncher remains stuck on tasks waiting for free nodes even if task is killed.
> ----------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-1398
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1398
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: tasktracker
>            Reporter: Hemanth Yamijala
>            Assignee: Amareshwari Sriramadasu
>             Fix For: 0.22.0
>
>         Attachments: patch-1398-1.txt, patch-1398-2.txt, patch-1398-ydist.txt, patch-1398.txt
>
>
> Tasks could be assigned to trackers for slots that are running other tasks in a commit pending state. This is an optimization done to pipeline task assignment and launch. When the task reaches the tracker, it waits until sufficient slots become free for it. This wait is done in the TaskLauncher thread. Now, while waiting, if the task is killed externally (maybe because the job finishes, etc), the TaskLauncher is not notified of this. So, it continues to wait for the killed task to get sufficient slots. If slots do not become free for a long time, this would result in considerable delay in waking up the TaskLauncher thread. If the waiting task happens to be a high RAM task, then it is also wasteful, because by waking up, it can make way for normal tasks that can run on the available number of slots.

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