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HDFS >> mail # user >> Re: reducer tasks start time issue


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Re: reducer tasks start time issue
Thanks Rishi,

My question is answered.

regards,
Lin

On Sun, Dec 23, 2012 at 12:09 AM, Rishi Yadav <[EMAIL PROTECTED]> wrote:

> Hi Lin,
>
> Reduce task starts as soon as output is ready from Mappers. The reduce
> method does not get called until all Mappers are done. If that's not the
> case, all operations which are not commutative and associative will yield
> incorrect result.
>
>
>
> Thanks and Regards,
>
> Rishi Yadav
>
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> On Sat, Dec 22, 2012 at 5:25 AM, Lin Ma <[EMAIL PROTECTED]> wrote:
>
>> Hi guys,
>>
>> Supposing in a Hadoop job, there are both mappers and reducers. My
>> question is, reducer tasks cannot begin until all mapper tasks complete? If
>> so, why designed in this way?
>>
>> thanks in advance,
>> Lin
>>
>
>
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB