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Date: Sat, 26 Jan 2013 07:01:14 +0000 (UTC)
From: "Jerry Chen (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Message-ID: <JIRA.12629228.1359098764854.195232.1359183674994@arcas>
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Subject: [jira] [Updated] (MAPREDUCE-4961) Map reduce running local should
 also go through ShuffleConsumerPlugin for enabling different MergeManager
 implementations
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     [ https://issues.apache.org/jira/browse/MAPREDUCE-4961?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jerry Chen updated MAPREDUCE-4961:
----------------------------------

    Release Note:   (was: Resubmit the patch for fixing the find bug warnings.)
    
> 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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