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MapReduce, mail # user - Re: Set the number of maps


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Re: Set the number of maps
Marcos Ortiz 2012-11-01, 18:03
The option since 0.21 was renamed to
mapreduce.tasktracker.map.tasks.maximum, and like
Harsh said to you, is is a TaskTracker service level option.

Another thing is that this option is very united to the
mapreduce.child.java.opts, so , make sure
to monitor constantly the effect of these changes in your cluster.

On 11/01/2012 11:55 AM, Harsh J wrote:
> It can't be set from the code this way - the slot property is applied
> at the TaskTracker service level (as the name goes).
>
> Since you're just testing at the moment, try to set these values,
> restart TTs, and run your jobs again. You do not need to restart JT at
> any point for tweaking these values.
>
> On Thu, Nov 1, 2012 at 7:13 PM, Cogan, Peter (Peter)
> <[EMAIL PROTECTED]> wrote:
>> Hi
>>
>> I understand that the maximum number of concurrent map tasks is set by
>> mapred.tasktracker.map.tasks.maximum  - however I wish to run with a smaller
>> number of maps (am testing disk IO). I thought that I could set that within
>> the main program using
>>
>> conf.set("mapred.tasktracker.map.tasks.maximuma", "4");
>>
>>
>> to run with 4 maps � but that seems to have no impact. I know I could just
>> change the mapred-site.xml and restart map reduce but that's kind of a pain.
>> Can it be set from within the code?
>>
>>
>> Thanks
>>
>> Peter
>
>

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