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https://issues.apache.org/jira/browse/MAPREDUCE-3902?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13447292#comment-13447292
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Tsuyoshi OZAWA commented on MAPREDUCE-3902:
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Thanks for your enumerating remaining tasks, Siddharth. I'll support you as far
as possible.
And I've not yet explained you the relationship between container-reuse work
and MAPREDUCE-4502, so it may confuse you. I'm sorry for the short of
explanation. I'll give it to you briefly. I'm planning to implement
MAPREDUCE-4502 and MAPREDUCE-4525 with container-reuse implementation, because
MRAppMaster in container-reuse implementation has the feature to monitor
whether the running tasks on the containers are "the last task at a machine or
not", for the purpose of exiting JVMs on containers, as you know. This feature
is very similar to monitor task progress per containers, for the purpose of
starting to run combiner for multi-level aggregation (MAPREDUCE-4502 and
MAPREDUCE-4525).
The description here is not documented, so I'll write down my thought as the
design note for MAPREDUCE-4502 and MAPREDUCE-4525 within next one week. I'm
very appreciate if you review it.
Thanks,
Tsuyoshi
> 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: Siddharth Seth
> Attachments: MAPREDUCE-3902.2.patch, 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) : MAPREDUCE-4525
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