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From Jothi Padmanabhan <joth...@yahoo-inc.com>
Subject Re: question about when shuffle/sort start working
Date Mon, 01 Jun 2009 04:26:31 GMT
When a Mapper completes, MapCompletionEvents are generated. Reducers try to
fetch map outputs for a given map only on the receipt of such events.


On 5/30/09 10:00 AM, "Jianmin Woo" <jianmin_woo@yahoo.com> wrote:

> Hi, 
> I am being confused by the protocol between mapper and reducer. When mapper
> emitting the (key,value) pair done, is there any signal the mapper send out to
> hadoop framework in protocol to indicate that map is done and the shuffle/sort
> can begin for reducer? If there is no this signal in protocol, when the
> framework begin the shuffle/sort?
> Thanks,
> Jianmin

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