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https://issues.apache.org/jira/browse/HADOOP-4018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12626842#action_12626842
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Devaraj Das commented on HADOOP-4018:
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Sorry Dhruba, I somehow missed the jira mail with your earlier comment.
I think we should do this in the server (if at all we want to do it) since this
should be a admin configured param. Also proper warning should be given as
response to the user if the JT discards a job because of too many splits..
Maybe we should maintain a global count of the tasks across all jobs as well
and if that is exceeded we don't accept any job till some job(s) complete..
By the way, configuring the mapred.jobtracker.completeuserjobs.maximum to a
lower value should help your case.
> 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
>
>
> 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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