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From Tom White <...@cloudera.com>
Subject Re: [DISCUSS] - YARN as a sub-project of Apache Hadoop
Date Thu, 26 Jul 2012 14:23:05 GMT
On Wed, Jul 25, 2012 at 9:40 PM, Arun C Murthy <acm@hortonworks.com> wrote:
> Folks,
> It's been nearly a year since we merged Hadoop YARN into trunk and we have made several
releases since.
> It's exciting to see various open-source communities (both in the ASF and externally)
start to explore integration with YARN such as Apache Hama, Apache Giraph, Apache S4, Spark
etc. This promises to help us realize our hopes of making Apache Hadoop a much more general
data processing platform (& storage, of course) and not tied to MapReduce alone for processing
data. Furthermore, we already have people contributing interesting prototypes such as DistributedShell
and PaaS on YARN.
> Given this, I think it would be useful to make YARN a sub-project of Apache Hadoop along
with Common, HDFS & MapReduce. I believe this would help other communities realize that
they could consider using YARN as a general-purpose resource management layer and help us
enhance YARN beyond it's humble beginnings.
> Clearly, YARN and MapReduce are different enough that they can and will attract a diverse
> I'd like to clarify that this proposal *does not* mean we move the code base out of hadoop/common/
tree. It just alleviates hadoop-yarn alongside hadoop-common, hadoop-hdfs & hadoop-mapreduce
in hadoop/trunk. Also, there would be *no changes* to release cycles - YARN would be co-released
with Common, HDFS & MapReduce.
> Thoughts?

+1 to the direction.

> ----
> What does it mean to the Hadoop developer community?
> # Project dependencies
> The change is that Hadoop would now have 4 sub-projects: Common, HDFS, YARN & MapReduce.
As today, the dependencies *do not change*:
> - Common is the base
> - HDFS depends only on Common
> - YARN depends only on Common & HDFS
> - MapReduce depends on Common, HDFS & YARN.

To be clear, these are runtime dependencies - YARN and MapReduce
should not have any compile-time dependencies on HDFS. See

> # Jira & Mailing lists
> We would have a separate YARN jira project and a yarn-dev@ mailing list.
> We already use separate MAPREDUCE jira issues for making changes to YARN (ResourceManager,
NodeManager) and to the MapReduce framework (MapReduce ApplicationMaster, MapReduce runtime
etc.). Hence, this isn't a much of a change.
> # Subversion
> Not much at all! YARN has, since the beginning, been developed with the understanding
that it is very independent of MapReduce and the code-bases are already independent i.e. hadoop-mapreduce-project/hadoop-yarn
and hadoop-mapreduce-project/hadoop-mapreduce-client.
> Essentially the change would be:
> $ svn mv hadoop-mapreduce-project/hadoop-yarn hadoop-yarn-project/hadoop-yarn
> ... and the necessary, albeit small, changes to our maven build infrastructure.

It would be good to eliminate the resulting redundant level in the
hierarchy at the same time: i.e.
hadoop-mapreduce-project/hadoop-mapreduce-client ->


> # Release Cycles
> No changes.
> YARN would be co-released with Common, HDFS & MapReduce, as is the case today.
> thanks,
> Arun

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