Hi Praveenesh, * You can set the maximum amount of reducers per node in your mapred-site.xml using mapred.tasktracker.reduce.tasks.maximum (default set to 2). * You can set the default number of reduce tasks with mapred.reduce.tasks (default set to 1 - this causes your single reducer). * Your job can try to override this setting by calling Job.setNumReduceTasks(INT) (http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/mapreduce/Job.html#setNumReduceTasks(int)).
Cheers, Evert > -----Original Message----- > From: modemide [mailto:[email protected]] > Sent: vrijdag 20 mei 2011 15:26 > To: [email protected] > Subject: Re: Why Only 1 Reducer is running ?? > > what does your mapred-site.xml file say? > > I've used wordcount and had close to 12 reduces running on a 6 > datanode cluster on a 3 GB file. > > > I have a configuration in there which says: > mapred.reduce.tasks = 12 > > The reason I chose 12 was because it was recommended that I choose 2x > number of tasktrackers. > > > > > > On 5/20/11, praveenesh kumar <[email protected]> wrote: > > Hello everyone, > > > > I am using wordcount application to test on my hadoop cluster of 5 > nodes. > > The file size is around 5 GB. > > Its taking around 2 min - 40 sec for execution. > > But when I am checking the JobTracker web portal, I am seeing only > one > > reducer is running. Why so ?? > > How can I change the code so that I will run multiple reducers also > ?? > > > > Thanks, > > Praveenesh > >
