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https://issues.apache.org/jira/browse/MAPREDUCE-4961?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13563539#comment-13563539
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Mariappan Asokan commented on MAPREDUCE-4961:
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Hi Jerry,
I agree with you that local jobs should also be supported by
{{ShuffleConsumerPlugin.}} However, we can simplify the patch if the default
implementation {{Shuffle}} itself calls the static method {{merge()}} in
{{Merger}} for the implementation of {{runLocal()}} mthod. There is no need to
change {{MergeManager.}} What do you think?
-- Asokan
> Map reduce running local should also go through ShuffleConsumerPlugin for
> enabling different MergeManager implementations
> -------------------------------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-4961
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4961
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: trunk
> Reporter: Jerry Chen
> Assignee: Jerry Chen
> Attachments: MAPREDUCE-4961.patch
>
> Original Estimate: 72h
> Remaining Estimate: 72h
>
> MAPREDUCE-4049 provide the ability for pluggable Shuffle and MAPREDUCE-4080
> extends Shuffle to be able to provide different MergeManager implementations.
> While using these pluggable features, I find that when a map reduce is
> running locally, a RawKeyValueIterator was returned directly from a static
> call of Merge.merge, which break the assumption that the Shuffle may provide
> different merge methods although there is no copy phase for this situation.
> The use case is when I am implementating a hash-based MergeManager, we don't
> need sort in map side, while when running the map reduce locally, the
> hash-based MergeManager will have no chance to be used as it goes directly to
> Merger.merge. This makes the pluggable Shuffle and MergeManager incomplete.
> So we need to move the code calling Merger.merge from Reduce Task to
> ShuffleConsumerPlugin implementation, so that the Suffle implementation can
> decide how to do the merge and return corresponding iterator.
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