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From Radhe Radhe <radhe.krishna.ra...@live.com>
Subject RE: Doubt regarding Binary Compatibility\Source Compatibility with old *mapred* APIs and new *mapreduce* APIs in Hadoop
Date Tue, 15 Apr 2014 20:35:46 GMT
Thanks Zhijie for the explanation.
Regarding #3 if I have ONLY the binaries i.e. jar file (compiled\build against old MRv1 mapred
APIS) then how can I compile it since I don't have the source code i.e. Java files. All I
can do with binaries i.e. jar file is execute it. 
-RR
Date: Tue, 15 Apr 2014 13:03:53 -0700
Subject: Re: Doubt regarding Binary Compatibility\Source Compatibility with old *mapred* APIs
and new *mapreduce* APIs in Hadoop
From: zshen@hortonworks.com
To: user@hadoop.apache.org

1. If you have the binaries that were compiled against MRv1 mapred libs, it should just work
with MRv2.2. If you have the source code that refers to MRv1 mapred libs, it should be compilable
without code changes. Of course, you're free to change your code.
3. If you have the binaries that were compiled against MRv1 mapreduce libs, it may not be
executable directly with MRv2, but you should able to compile it against MRv2 mapreduce libs
without code changes, and execute it.

- Zhijie

On Tue, Apr 15, 2014 at 12:44 PM, Radhe Radhe <radhe.krishna.radhe@live.com> wrote:




Thanks John for your comments,
I believe MRv2 has support for both the old *mapred* APIs and new *mapreduce* APIs.
I see this way:[1.]  One may have binaries i.e. jar file of the M\R program that used old
*mapred* APIs
This will work directly on MRv2(YARN).
[2.]  One may have the source code i.e. Java Programs of the M\R program that used old *mapred*
APIs
For this I need to recompile and generate the binaries i.e. jar file. Do I have to change
the old *org.apache.hadoop.mapred* APIs to new *org.apache.hadoop.mapreduce* APIs? or No code
changes are needed?

-RR
> Date: Mon, 14 Apr 2014 10:37:56 -0400
> Subject: Re: Doubt regarding Binary Compatibility\Source Compatibility with old *mapred*
APIs and new *mapreduce* APIs in Hadoop

> From: john.meagher@gmail.com
> To: user@hadoop.apache.org
> 

> Also, "Source Compatibility" also means ONLY a recompile is needed.
> No code changes should be needed.
> 
> On Mon, Apr 14, 2014 at 10:37 AM, John Meagher <john.meagher@gmail.com> wrote:

> > Source Compatibility = you need to recompile and use the new version
> > as part of the compilation
> >
> > Binary Compatibility = you can take something compiled against the old
> > version and run it on the new version

> >
> > On Mon, Apr 14, 2014 at 9:19 AM, Radhe Radhe
> > <radhe.krishna.radhe@live.com> wrote:
> >> Hello People,

> >>
> >> As per the Apache site
> >> http://hadoop.apache.org/docs/r2.3.0/hadoop-mapreduce-client/hadoop-mapreduce-client-core/MapReduce_Compatibility_Hadoop1_Hadoop2.html

> >>
> >> Binary Compatibility
> >> ====================
> >> First, we ensure binary compatibility to the applications that use old
> >> mapred APIs. This means that applications which were built against MRv1

> >> mapred APIs can run directly on YARN without recompilation, merely by
> >> pointing them to an Apache Hadoop 2.x cluster via configuration.
> >>
> >> Source Compatibility

> >> ====================
> >> We cannot ensure complete binary compatibility with the applications that
> >> use mapreduce APIs, as these APIs have evolved a lot since MRv1. However, we

> >> ensure source compatibility for mapreduce APIs that break binary
> >> compatibility. In other words, users should recompile their applications
> >> that use mapreduce APIs against MRv2 jars. One notable binary

> >> incompatibility break is Counter and CounterGroup.
> >>
> >> For "Binary Compatibility" I understand that if I had build a MR job with
> >> old *mapred* APIs then they can be run directly on YARN without and changes.

> >>
> >> Can anybody explain what do we mean by "Source Compatibility" here and also
> >> a use case where one will need it?
> >>
> >> Does that mean code changes if I already have a MR job source code written

> >> with with old *mapred* APIs and I need to make some changes to it to run in
> >> then I need to use the new "mapreduce* API and generate the new  binaries?
> >>
> >> Thanks,

> >> -RR
> >>
> >>
 		 	   		  


-- 
Zhijie ShenHortonworks Inc.http://hortonworks.com/





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