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Date: Sat, 18 Dec 2010 19:33:49 +0100
Message-ID: <AANLkTimm8UPP3ktP_uMBTBb2xEQ-fOLE97zZ=5HTO6Kv@mail.gmail.com>
Subject: Re: Passing messages
From: Martin Becker <_martinbecker@web.de>
To: mapreduce-user@hadoop.apache.org
Content-Type: text/plain; charset=ISO-8859-1

Thank you Ted,

I am using the 21.0 API so I would be drawing Counters from the
Context. So if a Counter is increased on a certain Reducer other
Reducers would retrieve that increased value when accessing the same
Counter? If so, then that is an interesting piece of information.

Unfortunately my threshold are doubles. I guess, I could find some
kind of conversion there. But is there any more general way to pass
information between Reducers?

Thanks,
Martin

On Sat, Dec 18, 2010 at 5:44 PM, Ted Yu <yuzhihong@gmail.com> wrote:
> In your reducer, you can utilize Reporter (getCounter and incrCounter
> methods) to pass this information between reducers.
>
> On Sat, Dec 18, 2010 at 8:04 AM, Martin Becker <_martinbecker@web.de> wrote:
>>
>> Hello everbody,
>>
>> I am wondering if there is a feature allowing (in my case) reduce
>> tasks to communicate. For example by some volatile variables at some
>> centralized point. Or maybe just notify other running or to-be-running
>> reduce tasks of a completed reduce task featuring some arguments.
>>
>> In my case, I have reduce tasks doing computations that will
>> output/produce certain quality threshold. Other reduce tasks can/could
>> estimate, if they ever get above those thresholds. If not they could
>> just cease running.
>>
>> Thanks in advance,
>> Martin
>>
>> PS: If such functions are not yet part of the API, I would like to
>> know if there are good reasons for it and if not, propose to introduce
>> such functionality.
>
>