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From "David Parks" <davidpark...@yahoo.com>
Subject RE: How can I limit reducers to one-per-node?
Date Sat, 09 Feb 2013 04:24:20 GMT
Hmm, odd, I’m using AWS Mapreduce, and this property is already set to 1 on my cluster by
default (using 15 m1.xlarge boxes which come with 3 reducer slots configured by default).




From: Nan Zhu [mailto:zhunansjtu@gmail.com] 
Sent: Saturday, February 09, 2013 10:59 AM
To: user@hadoop.apache.org
Subject: Re: How can I limit reducers to one-per-node?


I think set tasktracker.reduce.tasks.maximum  to be 1 may meet your requirement






Nan Zhu

School of Computer Science,

McGill University



On Friday, 8 February, 2013 at 10:54 PM, David Parks wrote:

I have a cluster of boxes with 3 reducers per node. I want to limit a particular job to only
run 1 reducer per node.


This job is network IO bound, gathering images from a set of webservers.


My job has certain parameters set to meet “web politeness” standards (e.g. limit connects
and connection frequency).


If this job runs from multiple reducers on the same node, those per-host limits will be violated.
 Also, this is a shared environment and I don’t want long running network bound jobs uselessly
taking up all reduce slots.


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