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From Varun saxena <varun.sax...@huawei.com>
Subject RE: [DISCUSS] merging YARN-2928 (Timeline Service v.2) to trunk
Date Tue, 21 Jun 2016 08:07:38 GMT
Thanks Karthik for sharing your views.

With regards to merging, it would help to have clear documentation on how to setup and use
--> We do have documentation on this. You and others who are interested can check out YARN-5174
which is the latest documentation related JIRA for ATSv2.

Slightly unrelated to the merge, do we plan to support any other simpler backend for users
to try out, in addition to HBase? LevelDB?
--> We do have a File System based implementation but it is strictly for test purposes
(as we write data into a local file). It does not support all the features of Timeline Service
v.2 as well.
Regarding LevelDB, Timeline Service v.2 has distributed writers and Level DB writes data (log
files or SSTable files) to local file system. This means there will be no easy way to have
a LevelDB based implementation because we would not know where to read the data from, especially
while fetching flow level information.
We can however, potentially change the Local File System based implementation to a HDFS based
implementation and have it as an alternate for non-production use, if there is a potential
need for it, based on community feedback. This however, would have to be further discussed
with the team.

Varun Saxena.

-----Original Message-----
From: Karthik Kambatla [mailto:kasha@cloudera.com] 
Sent: 21 June 2016 10:29
To: Sangjin Lee
Cc: yarn-dev@hadoop.apache.org
Subject: Re: [DISCUSS] merging YARN-2928 (Timeline Service v.2) to trunk

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

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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