[jira] [Commented] (HBASE-4914) Enhance MapReduce TableInputFormat to Support N-mappers per Region

["Cosmin Lehene (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-4914?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13231008#comment-13231008 ] 

Cosmin Lehene commented on HBASE-4914:
--------------------------------------

Hadoop 0.20 doesn't behave well with large number of map tasks, so we implemented a N-Regions per map (through a splits_per_map property). 

I guess ideally we should be able to specify a min/max number of map tasks as well and have these two happen implicitly, perhaps with some sane thresholds.
                
> Enhance MapReduce TableInputFormat to Support N-mappers per Region
> ------------------------------------------------------------------
>
>                 Key: HBASE-4914
>                 URL: https://issues.apache.org/jira/browse/HBASE-4914
>             Project: HBase
>          Issue Type: Sub-task
>          Components: client, regionserver
>            Reporter: Nicolas Spiegelberg
>            Priority: Blocker
>             Fix For: 0.94.0
>
>
> Current TableInputFormat based MR jobs create exactly one mapper per region where each mapper sets one Scan with appropriate start/stop row keys. This change allows jobs to be run with any number of mappers per region, so that when a mapper fails, there will be less data to be reprocessed.

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