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From aniket ray <aniket....@gmail.com>
Subject Re: Capacity scheduler and map/reduce jobs
Date Wed, 15 Sep 2010 10:54:49 GMT
On Tue, Sep 14, 2010 at 1:45 AM, Arun C Murthy <acm@yahoo-inc.com> wrote:

> Moving mapreduce-user@, bcc common-user@. Please use the appropriate
> project lists for discussions.
> On Sep 13, 2010, at 1:47 AM, aniket ray wrote:
>  I see that the reduces of Queue 1 don't start till maps of Job 2 are over
>> (even though maps of Job 1 are complete). I am not able to understand
>> this behavior and feel that this may be a configuration issue that I am
>> missing. Since they are independent tasks and capacity is free, shouldn't
>> reduce tasks of Queue kick in?
> This shouldn't happen in the CS. Maybe you are hitting 'slowstart' for the
> reduces of Job1?
> From src/mapred/mapred-default.xml:
> <property>
>  <name>mapred.reduce.slowstart.completed.maps</name>
>  <value>0.05</value>
>  <description>Fraction of the number of maps in the job which should be
>  complete before reduces are scheduled for the job.
>  </description>
> </property>
>  I've been trying to run some map/reduce jobs in parallel using the
>> capacity
>> scheduler on hadoop 0.20.2.
> The CS in 0.20.2 is quite dated, you might want to use the Yahoo! GitHub (
> http://github.com/yahoo/hadoop-common) for the latest version of the CS.
> Thanks. I used this version of hadoop with its capacity scheduler and
things work great. I saw a major performance boost.
There is one hit I'm not able to figure out using this version though. Jobs
stay in the queue in a "waiting state" (According to console dump and the
web UI) for much longer, even if no other jobs are running in the queue.

I'm currently working to get the Yahoo codebase released as an Apache
> Release (maybe hadoop-0.20-security), once we get that done you should be
> able to use the latest CapacityScheduler via an Apache Release.
> Arun

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