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MapReduce >> mail # user >> Set reducer capacity for a specific M/R job


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Set reducer capacity for a specific M/R job
Hi,

I want to change the cluster's capacity of reduce slots on a per job basis.
Originally I have 8 reduce slots for a tasktracker.
I did:

conf.set("mapred.tasktracker.reduce.tasks.maximum", "4");
...
Job job = new Job(conf, ...)
And in the web UI I can see that for this job, the max reduce tasks is
exactly at 4, like I set. However hadoop still launches 8 reducer per
datanode ... why is this?

How could I achieve this?
--
*JU Han*

Software Engineer Intern @ KXEN Inc.
UTC   -  Université de Technologie de Compiègne
*     **GI06 - Fouille de Données et Décisionnel*

+33 0619608888
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB