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From "Amar Kamat (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4018) limit memory usage in jobtracker
Date Wed, 24 Sep 2008 11:48:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12634113#action_12634113
] 

Amar Kamat commented on HADOOP-4018:
------------------------------------

Few comments :

_Main :_

1. There is no need to do the cleanup in init tasks. Simply throwing an exception in init
tasks should do the cleanup and kill/fail the job. There seems to be a bug in the framework
and I have opened HADOOP-4261 to address it. 
2. mapred.max.tasks.per.job should be set at the jobtracker level and not at the job level.
It should be something like an expert-final parameter

_Testcase :_
1. Remove the commented assert statement
2. Most of the imports are not needed. 
3. Rewrite the test to reflect the changes

> limit memory usage in jobtracker
> --------------------------------
>
>                 Key: HADOOP-4018
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4018
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>         Attachments: maxSplits.patch, maxSplits2.patch, maxSplits3.patch, maxSplits4.patch,
maxSplits5.patch, maxSplits6.patch, maxSplits7.patch, maxSplits8.patch
>
>
> We have seen instances when a user submitted a job with many thousands of mappers. The
JobTracker was running with 3GB heap, but it was still not enough to prevent memory trashing
from Garbage collection; effectively the Job Tracker was not able to serve jobs and had to
be restarted.
> One simple proposal would be to limit the maximum number of tasks per job. This can be
a configurable parameter. Is there other things that eat huge globs of memory in job Tracker?

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