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From "Ahmed Radwan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-4304) Deadlock where all containers are held by ApplicationMasters should be prevented
Date Fri, 01 Jun 2012 23:00:24 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4304?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13287762#comment-13287762
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Ahmed Radwan commented on MAPREDUCE-4304:
-----------------------------------------

But, even for the capacity scheduler, what is a good strategy for tuning this property especially
when there are variability in the sizes of jobs, and the resources they require? This can
be really hard, and can endup in either an underutilization of the cluster or the described
deadlock.

A possible approach will be preemption of AM containers if their resource requirements cannot
be fulfilled within a period of time, they can go back to the queue and only restarted when
there are resources. The scheduler can keep track of required resources to avoid recomputation
of resources when the AM is restarted. Thoughts?
                
> Deadlock where all containers are held by ApplicationMasters should be prevented
> --------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-4304
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4304
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: mrv2, resourcemanager
>    Affects Versions: 0.23.1
>            Reporter: Herman Chen
>
> In my test cluster with 4 NodeManagers, each with only ~1.6G container memory, when a
burst of jobs, e.g. >10, are concurrently submitted, it is likely that 4 jobs are accepted,
with 4 ApplicationMasters allocated, but then the jobs block each other indefinitely because
they're all waiting to allocate more containers.
> Note that the problem is not limited to tiny cluster like this.  As long as the number
of jobs being submitted is greater than the rate jobs finish, it may run into a vicious cycle
where more and more containers are locked up by ApplicationMasters.

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