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From jiang licht <licht_ji...@yahoo.com>
Subject Re: specify number of mappers/reducers per node per job?
Date Thu, 21 Oct 2010 18:37:30 GMT
Actually I believe this cannot be achieved by current m/r scheduler since as I understand,
a scheduler can only control how much resource in total to be assigned to a job but it does
not allow external control which node a mapper/reducer will run on, which is reasonable (jobtracker
has to base its task assignment on the current status of the cluster, like if a node is blacklisted,
then you cannot run any tasks on it).

Thanks,

Michael

--- On Thu, 10/21/10, jiang licht <licht_jiang@yahoo.com> wrote:

From: jiang licht <licht_jiang@yahoo.com>
Subject: Re: specify number of mappers/reducers per node per job?
To: common-user@hadoop.apache.org
Date: Thursday, October 21, 2010, 12:38 PM

Thanks, Harsh.

That's my suspect as well. It's part of what a schedule is responsible for, s.a. capacity
scheduler. Want to make sure I didn't miss it if there is another node-wise property at job-level
to limit resource available to a job in parallel with "mapred.tasktracker.*.tasks.maximum".

Thanks,

Michael

--- On Thu, 10/21/10, Harsh J <qwertymaniac@gmail.com> wrote:

From: Harsh J <qwertymaniac@gmail.com>
Subject: Re: specify number of mappers/reducers per node per job?
To: common-user@hadoop.apache.org
Date: Thursday, October 21, 2010, 1:03 AM

AFAIK there is no way to control this from a job submission perspective.
Maybe the scheduler concept in Hadoop MapReduce can help you.

--
Harsh J
http://www.harshj.com

On Oct 21, 2010 6:32 AM, "jiang licht" <licht_jiang@yahoo.com> wrote:

Is there a way to control maximum number of mappers or reducers per node per
job? i.e. say I have a cluster, now I want
 to run a job such that on each
node, no more than 2 mappers are expected to run at the same time (but
maximum numbers of m/r slots on a node are some bigger numbers specified by
"mapred.tasktracker.map.tasks.maximum",
"mapred.tasktracker.reduce.tasks.maximum").

Thanks,

Michael



      


      
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