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From Karthik Kambatla <ka...@cloudera.com>
Subject Re: [DISCUSS] merging YARN-2928 (Timeline Service v.2) to trunk
Date Tue, 21 Jun 2016 02:29:07 GMT
Firstly, thanks Sangjin and others for driving this major feature.

Merging to trunk and including in 3.0.0-alpha1 seems reasonable, as it will
give early access to downstream users.

With regards to merging, it would help to have clear documentation on how
to setup and use ATS.

Slightly unrelated to the merge, do we plan to support any other simpler
backend for users to try out, in addition to HBase? LevelDB? I understand
this wouldn't scale, but would it help with initial adoption and feedback
from early users?

On Mon, Jun 20, 2016 at 10:26 AM, Sangjin Lee <sjlee@apache.org> wrote:

> Hi all,
> I’d like to open a discussion on merging the Timeline Service v.2 feature
> to trunk (YARN-2928 and MAPREDUCE-6331) [1][2]. We have been developing the
> feature in a feature branch (YARN-2928 [3]) for a while, and we are
> reasonably confident that the state of the feature meets the criteria to be
> merged onto trunk and we'd love folks to get their hands on it and provide
> valuable feedback so that we can make it production-ready.
> In a nutshell, Timeline Service v.2 delivers significant scalability and
> usability improvements based on a new architecture. You can browse the
> requirements/design doc, the storage schema doc, the new entity/data model,
> the YARN documentation, and also discussions on subsequent milestones on
> YARN-2928 [1].
> What we would like to merge to trunk is termed "alpha 1" (milestone 1). The
> feature has a complete end-to-end read/write flow, and you should be able
> to start setting it up and testing it. At a high level, the following are
> the key features that have been implemented:
> - distributed writers (collectors) as NM aux services
> - HBase storage
> - new entity model that includes flows
> - setting the flow context via YARN app tags
> - real time metrics aggregation to the application level and the flow level
> - rich REST API that supports filters, complex conditionals, limits,
> content selection, etc.
> - YARN generic events and system metrics
> - integration with Distributed Shell and MapReduce
> There are a total of 139 subtasks that were completed as part of this
> effort.
> We paid close attention to ensure that once disabled Timeline Service v.2
> does not impact existing functionality when disabled (by default).
> I'd like to call out a couple of things to discuss in particular.
> *First*, if the merge vote is approved, to which branch should this be
> merged and what would be the release version? My preference is that *it
> would be merged to branch "trunk" and be part of 3.0.0-alpha1* if approved.
> Since the 3.0.0-alpha1 is in active progress, I wanted to get your thoughts
> on this.
> *Second*, Timeline Service v.2 introduces a dependency on HBase from YARN.
> It is not a cyclical dependency (as HBase does not really depend on YARN).
> However, the version of Hadoop that HBase currently supports lags behind
> the Hadoop version that Timeline Service is based on, so there is a
> potential for subtle dependency conflicts. We made some efforts to isolate
> the issue (see [4] and [5]). The HBase folks have also been responsive in
> keeping up with the trunk as much as they can. Nonetheless, this is
> something to keep in mind.
> I would love to get your thoughts on these and more before we open a real
> voting thread. Thanks!
> Regards,
> Sangjin
> [1] YARN-2928: https://issues.apache.org/jira/browse/YARN-2928
> [2] MAPREDUCE-6331: https://issues.apache.org/jira/browse/MAPREDUCE-6331
> [3] YARN-2928 commits: https://github.com/apache/hadoop/commits/YARN-2928
> [4] YARN-5045: https://issues.apache.org/jira/browse/YARN-5045
> [5] YARN-5071: https://issues.apache.org/jira/browse/YARN-5071

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