You can specify that a group of keys should go to the same host for reducing, but I have never encountered any situation where you need to know beforehand exactly which host a particular key should go to. I am not sure if that can be done. Just out of curiosity, why do you need this kind of control over reduction?
Hari On Sat, Dec 18, 2010 at 11:54 PM, Jane Chen <jxchen_us_1...@yahoo.com>wrote: > But how does this help me request which *host* to schedule the reduce task > to? > Thanks, > Jane > > --- On *Sat, 12/18/10, Hari Sreekumar <hsreeku...@clickable.com>* wrote: > > > From: Hari Sreekumar <hsreeku...@clickable.com> > Subject: Re: How to Influence Reduce Task Location. > To: mapreduce-user@hadoop.apache.org > Date: Saturday, December 18, 2010, 10:16 AM > > > Hi Jane, > > The partitioner class can be used to achieve this. ( > http://hadoop.apache.org/mapreduce/docs/r0.21.0/api/org/apache/hadoop/mapreduce/Partitioner.html > ). > > Thanks, > Hari > > On Sat, Dec 18, 2010 at 11:13 PM, Jane Chen > <jxchen_us_1...@yahoo.com<http://us.mc509.mail.yahoo.com/mc/compose?to=jxchen_us_1...@yahoo.com> > > wrote: > > Hi All, > > Is there anyway to influence where a reduce task is run? We have a case > where we'd like to choose the host to run the reduce task based on the > task's input key. > > Any suggestion is greatly appreciated. > > Thanks, > Jane > > > > > >
