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From xeon Mailinglist <xeonmailingl...@gmail.com>
Subject Re: What is the class that launches the reducers?
Date Fri, 26 Aug 2016 06:07:20 GMT
Right now the map and reduce task produces digests of the output. This
logic is inside the map and reduce functions. I need to pause the execution
when all maps finish because there will be an external program that is
synchronizing several mapreduce runtimes. When all map tasks finish from
the several jobs, the map output will be verified. Then, this external
program will resume the execution.

I really want to create a knob in mapreduce by modifying the source code,
because with this knob I can exclude the identity maps execution and boost
the performance. I think the devs should create this feature.

Anyway, I am looking in the source code for the part where reduce tasks are
set to launch. Does anyone know which class launches the reduce tasks in
mapreduce v2?

On Aug 26, 2016 02:07, "Daniel Templeton" <daniel@cloudera.com> wrote:

> How are you intending to verify the map output?  It's only partially
> dumped to disk.  None of the intermediate data goes into HDFS.
>
> Daniel
>
> On Aug 25, 2016 4:10 PM, "xeon Mailinglist" <xeonmailinglist@gmail.com>
> wrote:
>
>> But then I need to set identity maps to run the reducers. If I suspend a
>> job after the maps finish, I don't need to set identity maps up. I want to
>> suspend a job so that I don't run identity maps and get better
>> performance.
>>
>> On Aug 25, 2016 10:12 PM, "Haibo Chen" <haibochen@cloudera.com> wrote:
>>
>> One thing you can try is to write a map-only job first and then verify the
>> map out.
>>
>> On Thu, Aug 25, 2016 at 1:18 PM, xeon Mailinglist <
>> xeonmailinglist@gmail.com
>> > wrote:
>>
>> > I am using Mapreduce v2.
>> >
>> > On Aug 25, 2016 8:18 PM, "xeon Mailinglist" <xeonmailinglist@gmail.com>
>> > wrote:
>> >
>> > > I am trying to implement a mechanism in MapReduce v2 that allows to
>> > > suspend and resume a job. I must suspend a job when all the mappers
>> > finish,
>> > > and resume the job from that point after some time. I do this,
>> because I
>> > > want to verify the integrity of the map output before executing the
>> > > reducers.
>> > >
>> > > I am looking for the class that tells when the Reduce tasks should
>> start.
>> > > Does anyone know where is this?
>> > >
>> >
>>
>

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