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https://issues.apache.org/jira/browse/MAPREDUCE-4808?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13555211#comment-13555211
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Alejandro Abdelnur commented on MAPREDUCE-4808:
-----------------------------------------------
The goal is to be able to write alternate implementations of the Shuffle, like
the ones Asokan and Jerry are trying to do, while reusing functionality
provided by the Hadoop default implementation. For example, being able to
leverage the logic in the default shuffle (ie fetchers), while replacing the
merge logic and merge resources allocation logic driven by the MergeManager.
While some of this logic replacement could be done at Merge level as you
suggested, other, like MapOutput allocation cannot be done there as this is
driven by the MergeManager. The refactoring of MapOutput allocation from struct
to classes permits alternate implementations that can reuse memory buffers
thus reducing JVM heap allocation.
> Refactor MapOutput and MergeManager to facilitate reuse by Shuffle
> implementations
> ----------------------------------------------------------------------------------
>
> Key: MAPREDUCE-4808
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4808
> Project: Hadoop Map/Reduce
> Issue Type: New Feature
> Affects Versions: 2.0.2-alpha
> Reporter: Arun C Murthy
> Assignee: Mariappan Asokan
> Fix For: 2.0.3-alpha
>
> Attachments: COMBO-mapreduce-4809-4812-4808.patch,
> mapreduce-4808.patch, mapreduce-4808.patch, mapreduce-4808.patch,
> mapreduce-4808.patch, mapreduce-4808.patch, mapreduce-4808.patch,
> mapreduce-4808.patch, MergeManagerPlugin.pdf
>
>
> Now that Shuffle is pluggable (MAPREDUCE-4049), it would be convenient for
> alternate implementations to be able to reuse portions of the default
> implementation.
> This would come with the strong caveat that these classes are LimitedPrivate
> and Unstable.
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