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MapReduce >> mail # user >> When and who move the reduce output file part-0000X to the final output directory


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Ling Kun 2013-05-10, 03:19
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Harsh J 2013-05-10, 05:26
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Re: When and who move the reduce output file part-0000X to the final output directory
Thanks Harsh!
your reply helps me a lot.

Kun Ling
On Fri, May 10, 2013 at 1:26 PM, Harsh J <[EMAIL PROTECTED]> wrote:

> The task itself moves it when it receives a commitTask message. See
> the OutputCommitter class:
>
> http://hadoop.apache.org/docs/current/api/org/apache/hadoop/mapred/OutputCommitter.html#commitTask(org.apache.hadoop.mapred.TaskAttemptContext)
>
> On Fri, May 10, 2013 at 8:49 AM, Ling Kun <[EMAIL PROTECTED]> wrote:
> > Dear all,
> >
> >      I am looking into the MR work flow, and want to know more details
> about
> > the reduce output data copy .
> >
> >     Here is my question.
> >
> >    For the DFSIO test or some other MR jobs. Each reduce task will run
> on a
> > TT, and generate files to some dirs named like this:  "
> > XXX//_temporary/_attempt_201305101045_0005_r_000000_0/", there will also
> be
> > a result file named part-00000.
> >
> >   After the reducer done the task. the reducer output data part-00000
> should
> > be moved from  the local disk to the HDFS.
> >
> > My question is: Is that the time that when reducer finish the task that
> > part-00000 will be copied to the HDFS? Who make this file copy happen?
> The
> > Reducer child? The TaskTracker which run the reduce task? Or the
> JobTracker?
> >
> > Thanks,
> >
> > yours,
> > Kun Ling
> >
> > --
> > http://www.lingcc.com
>
>
>
> --
> Harsh J
>

--
http://www.lingcc.com