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https://issues.apache.org/jira/browse/MAPREDUCE-3902?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arun C Murthy updated MAPREDUCE-3902:
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Summary: MR AM should reuse containers for map tasks, there-by allowing
fine-grained control on num-maps for users without need for
CombineFileInputFormat etc. (was: MR AM should reuse containers for map tasks)
bq. Is there a cap on the amount of re-use? For example, if the container has
been in use for more than 1 minute then do not re-use it.
Not currently, but we could add something like this - except it won't make too
much difference since you need to run the remaining maps in other containers
anyway! :)
bq. Or to rephrase, what prevents a cluster with a few large jobs from having
hogged containers?
The central scheduler (e.g CapacityScheduler) already uses queue-capacities and
user-limits, (and in future, preemption) to prevent this.
> MR AM should reuse containers for map tasks, there-by allowing fine-grained
> control on num-maps for users without need for CombineFileInputFormat etc.
> ------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-3902
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-3902
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: applicationmaster, mrv2
> Reporter: Arun C Murthy
> Assignee: Arun C Murthy
> Attachments: MAPREDUCE-3902.patch
>
>
> The MR AM is now in a great position to reuse containers across (map) tasks.
> This is something similar to JVM re-use we had in 0.20.x, but in a
> significantly better manner:
> # Consider data-locality when re-using containers
> # Consider the new shuffle - ensure that reduces fetch output of the whole
> container at once (i.e. all maps)
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