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From "Hemanth Yamijala (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4981) Prior code fix in Capacity Scheduler prevents speculative execution in jobs
Date Mon, 18 May 2009 11:17:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4981?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12710335#action_12710335
] 

Hemanth Yamijala commented on HADOOP-4981:
------------------------------------------

+1 for the code changes. One minor point is to comment in the test case for the Fake objects
that we are supporting only 1 speculative map / reduce at this point. I think this is enough
for now. We can expand as needed.

> Prior code fix in Capacity Scheduler prevents speculative execution in jobs
> ---------------------------------------------------------------------------
>
>                 Key: HADOOP-4981
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4981
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: contrib/capacity-sched
>            Reporter: Vivek Ratan
>         Attachments: 4981.1.patch, 4981.2.patch, HADOOP-4981-1.patch, HADOOP-4981-2.patch,
HADOOP-4981-3.patch, HADOOP-4981-4.patch
>
>
> As part of the code fix for HADOOP-4035, the Capacity Scheduler obtains a task from JobInProgress
(calling obtainNewMapTask() or obtainNewReduceTask()) only if the number of pending tasks
for a job is greater than zero (see the if-block in TaskSchedulingMgr.getTaskFromJob()). So,
if a job has no pending tasks and only has running tasks, it will never be given a slot, and
will never have a chance to run a speculative task. 

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