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From "Tsuyoshi OZAWA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-4502) Multi-level aggregation with combining the result of maps per node/rack
Date Fri, 07 Sep 2012 16:14:08 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4502?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13450752#comment-13450752
] 

Tsuyoshi OZAWA commented on MAPREDUCE-4502:
-------------------------------------------

After debating with Siddharsh, I decided to implement combining against current trunk branch.
I'll attach the architecture overview and design note as soon as possible(maybe day after
tomorrow).
                
> Multi-level aggregation with combining the result of maps per node/rack
> -----------------------------------------------------------------------
>
>                 Key: MAPREDUCE-4502
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4502
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: applicationmaster, mrv2
>            Reporter: Tsuyoshi OZAWA
>            Assignee: Tsuyoshi OZAWA
>
> The shuffle costs is expensive in Hadoop in spite of the existence of combiner, because
the scope of combining is limited within only one MapTask. To solve this problem, it's a good
way to aggregate the result of maps per node/rack by launch combiner.
> This JIRA is to implement the multi-level aggregation infrastructure, including combining
per container(MAPREDUCE-3902 is related), coordinating containers by application master without
breaking fault tolerance of jobs.

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