That is a per job property and you can raise it when submitting a job itself.
You can pass it via -D args (See http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/util/Tool.html) or via a conf.set(name, value) from inside the code. Mostly, any prop that is not of the format mapred(uce).{jobtracker,tasktracker}.* aren't going to be requiring a restart of services. On Wed, Jun 13, 2012 at 6:24 PM, Matthias Zengler <matthias.zeng...@googlemail.com> wrote: > I want to change the mapreduce.(map|reduce).java.opts for a bigger heap > space of my map and reduce parts. > > 2012/6/13 Harsh J <ha...@cloudera.com> > >> Matthias, >> >> It depends on what config you're trying to change. There are several >> per-job configs that do not require changes on JT/TT mapred-site.xml >> and can be passed via -D parameters to a job's configuration directly >> from CLI (if you use the Tool and ToolRunner methods of writing a >> driver), or manually via the JobConf/Job.getConfiguration() objects >> inside the code. >> >> So question to you: Which set of configs are you wishing to change >> every job run? Cause only config changes that apply to JT or TTs need >> those services to be restarted, the rest can be applied on a per job >> basis, without requiring a restart of anything. >> >> On Wed, Jun 13, 2012 at 5:50 PM, Matthias Zengler >> <matthias.zeng...@googlemail.com> wrote: >> > Hi, >> > >> > I've got a question regarding hadoop configuration. Is it possible to >> pass >> > configuration parameters on job start up? >> > Something like that: >> > >> > hadoop -HADOOP_HEAPSIZE=4G jar some.jar some.class.to.execute param1 >> param2 >> > >> > Or do I have to restart the hadoop cluster every time I want to change >> > something even if it is just for a specific job or workflow? >> > We have some jobs running which needs a lot of time and we want to start >> > another one with a slightly different configuration because it needs more >> > memory to finish. >> > We are using CDH3. >> > >> > Greetings, >> > Mat >> >> >> >> -- >> Harsh J >> -- Harsh J
