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From "Vinod Kumar Vavilapalli (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MAPREDUCE-5221) Reduce side Combiner is not used when using the new API
Date Wed, 15 May 2013 22:31:18 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-5221?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vinod Kumar Vavilapalli updated MAPREDUCE-5221:
-----------------------------------------------

    Status: Open  (was: Patch Available)

Thanks for taking this up, Tsuyoshi!

Comments on your patch:
 - In ReduceTask.getCombinerClass(), there is a lot of implicit type-casting. I am not sure
if this will even work. getCombinerClass(), the variable clazz pointing to shuffle-plugin
and ShuffleConsumerPlugin.Context all take in a Class<? extends Reducer> which won't
be true for the new combiner. Did you test this at all? Can you please run a job with a new
combiner with the patch? I doubt that it works.
 - Please fix the typos "Cominer" in the tests.
 - May be also add another simple test to verify if both new and old combiners are set.
 - Move this test code to the existing mapred.TestReduceTask.

                
> Reduce side Combiner is not used when using the new API
> -------------------------------------------------------
>
>                 Key: MAPREDUCE-5221
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5221
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>    Affects Versions: 2.0.4-alpha
>            Reporter: Siddharth Seth
>            Assignee: Tsuyoshi OZAWA
>         Attachments: MAPREDUCE-5221.1.patch, MAPREDUCE-5221.2.patch, MAPREDUCE-5221.3.patch
>
>
> If a combiner is specified using o.a.h.mapreduce.Job.setCombinerClass - this will silently
ignored on the reduce side since the reduce side usage is only aware of the old api combiner.
> This doesn't fail the job - since the new combiner key does not deprecate the old key.

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