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From Bikas Saha <bi...@hortonworks.com>
Subject RE: [DISCUSS] Publishing and releasing jars for different hadoop version dependencies
Date Sun, 08 Mar 2015 21:54:50 GMT
As an aside, Flink could consider moving to a more current version. There have been many key
improvements in Timeline Server, preemption, node labels, resource monitoring etc. that users
may want to take advantage of.

If Tez publishes Hadoop version specific binaries to maven then Flink and others may be able
to consume them directly during development.

Bikas

-----Original Message-----
From: Robert Metzger [mailto:rmetzger@apache.org] 
Sent: Sunday, March 08, 2015 6:40 AM
To: dev@tez.apache.org
Subject: Re: [DISCUSS] Publishing and releasing jars for different hadoop version dependencies

Hi Hitesh,

I've talked about this with Kostas, let me check on some of our assumptions.

You can compile Flink against a hadoop1 and hadoop2 profile. We would include flink-on-tez
only into our (default) hadoop2 profile.
For that profile, we use Hadoop 2.2.0.

You can see on maven central, that we publish two versions of each flink module for each release,
a 0.8.1-hadoop1 and a 0.8.1 version.
This way users from both Hadoop APIs can use our system.

Adding Tez as a dependency to Flink (hadoop2) would cause a dependency conflict on the Hadoop
version. Our parent pom enforces Hadoop 2.2.0 for all dependencies, so we force Tez to use
Hadoop 2.2.0 as well.
In my understanding the compilation fails in that case.

If there would be a Tez version compatible with Hadoop 2.2.0 in mvn central, we could add
the "flink-on-tez" module to maven central.

If thats not possible, users who want to use Flink-on-Tez have to compile Flink against Hadoop
2.6.0 themselves. Its only one maven command, but less convenient than something on mvn central.


On Fri, Mar 6, 2015 at 8:03 PM, Hitesh Shah <hitesh@apache.org> wrote:

> Thanks for the feedback, Kostas,
>
> One clarification though - are you saying Tez should publish jars to 
> maven central built against different versions of Hadoop? If yes, is 
> this mainly due to the hadoop dependencies that Tez pulls in or due to 
> any incompatibilities that you have noticed?
>
> thanks
> — Hitesh
>
>
> On Mar 6, 2015, at 9:03 AM, Kostas Tzoumas <ktzoumas@apache.org> wrote:
>
> > Publishing jars for different Hadoop dependencies, and in particular 
> > for Hadoop 2.2 would also be beneficial for Flink on Tez as we offer 
> > maven archetypes for users to create Flink applications.  Currently, 
> > we need to ask users that want to run Flink apps with Tez as backend 
> > to compile the Flink code themselves due to a Hadoop version mismatch.
> >
> >
> >
> > On Thu, Mar 5, 2015 at 1:46 AM, Hitesh Shah <hitesh@apache.org> wrote:
> >
> >> From an ASF perspective, verifiable releases are only source releases.
> The
> >> binaries are just convenience artifacts that can also made 
> >> available
> with a
> >> given release. Hence in terms of supporting multiple hadoop 
> >> versions,
> we do
> >> want to allow various users/distros to compile Tez against their
> particular
> >> version of hadoop.
> >>
> >> From a run-time point of view , if Tez compiled against hadoop-2.6 
> >> is
> run
> >> on a 2.4 cluster, it should work normally as long as acls are 
> >> disabled ( via tez config tez.am.acls.enabled ). That said, there 
> >> are probably some improvements that could be done to handle the 
> >> case where acls are
> enabled
> >> on a 2.4 cluster in a more cleaner manner.
> >>
> >> thanks
> >> — Hitesh
> >>
> >> On Mar 4, 2015, at 9:21 AM, Chris K Wensel <chris@wensel.net> wrote:
> >>
> >>> compile what against hadoop 2.4? Tez? Hopefully no one except Tez 
> >>> devs
> >> ever compile Tez (once the apache committers offer up pre-built
> binaries, I
> >> only ever do for this reason).
> >>>
> >>> if compiling application code against Tez and Hadoop 2.4, the jar 
> >>> won't
> >> come into play unless running tests (so i believe).
> >>>
> >>> I would then enhance option two to gracefully fail if -acls (the
> >> Manager) is not applicable (on hadoop 2.4) but mistakenly included 
> >> in
> the
> >> 2.4 classpath (testing app code against hadoop 2.4)
> >>>
> >>> of course then this is really option 1 now with two jars.
> >>>
> >>> ckw
> >>>
> >>>> On Mar 2, 2015, at 3:05 PM, Hitesh Shah <hitesh@apache.org> wrote:
> >>>>
> >>>> Thanks for the suggestions, Chris. Filed TEZ-2168 for this.
> >>>>
> >>>> At this point, I am inclined to follow option 2 mainly to retain 
> >>>> the
> >> ability for users to compile against hadoop 2.4. I am not sure if 
> >> there
> is
> >> a simple and performant way ( without using reflection for all 2.6
> specific
> >> calls ) to retain compile compatibility with option 1.
> >>>>
> >>>> Any other comments for other folks on this issue in general or on 
> >>>> the
> 2
> >> options that Chris suggested?
> >>>>
> >>>> thanks
> >>>> — Hitesh
> >>>>
> >>>>
> >>>> On Feb 26, 2015, at 1:18 PM, Chris K Wensel <chris@wensel.net>
wrote:
> >>>>
> >>>>> The immediate issue is having two mutually exclusive artifacts:
> >> tez-yarn-timeline-history and tez-yarn-timeline-history
> >>>>>
> >>>>> outside of ATSHistoryACLPolicyManager, the code is identical. 
> >>>>> just
> the
> >> dependencies are changed.
> >>>>>
> >>>>> TezClient attempts to load this Manager, under the assumption if

> >>>>> it
> >> exists, it is running on hadoop 2.6. (running on 2.4 is fatal)
> >>>>>
> >>>>> My recommendation would be never to change artifact names (or
> >> conditionally choose them) inside of major releases, but accreting 
> >> new, optional, ones as versions progress is fine.
> >>>>>
> >>>>> thus I would either:
> >>>>>
> >>>>> create a single artifact tez-yarn-timeline-history compiled with

> >>>>> a
> >> default dep of hadoop 2.6, that includes the Manager. update the
> TezClient
> >> code to gracefully fail if the Manager is not applicable (the 
> >> runtime
> env
> >> is Hadoop 2.4).
> >>>>>
> >>>>> or
> >>>>>
> >>>>> offer tez-yarn-timeline-history-with-acls as an optional 
> >>>>> artifact for
> >> Hadoop 2.6 deployments, with the single Manager class in it, which 
> >> in
> turn
> >> requires the tez-yarn-timeline-history artifact -- which is 
> >> sufficient
> for
> >> a 2.4 runtime. if the user provides the additional -with-acls 
> >> artifact, they are knowingly going to have problems on Hadoop 2.4.
> >>>>>
> >>>>> I prefer the first as it keeps my build file simple. graceful
> >> degradation of services per environment (with appropriate logging) 
> >> is a well accepted practice.
> >>>>>
> >>>>> and you can now test Tez across multiple versions Hadoop/Yarn at
> >> runtime (outside of compile time).
> >>>>>
> >>>>> we do this with Cascading, just simple build file modifications

> >>>>> to
> >> verify binary compatibility (vendors fork this repo to verify their 
> >> distributions, and been known to find critical bugs):
> >>>>>
> >>>>> https://github.com/Cascading/cascading.compatibility
> >>>>>
> >>>>> ckw
> >>>>>
> >>>>>> On Feb 26, 2015, at 11:03 AM, Hitesh Shah <hitesh@apache.org>
> wrote:
> >>>>>>
> >>>>>> Hi folks,
> >>>>>>
> >>>>>> Chris raised a good point earlier in terms of publishing jars

> >>>>>> for
> use
> >> against different versions of hadoop. For the most part, I think we 
> >> have done well to ensure that the user-facing modules are version 
> >> agnostic
> but
> >> the same does not hold for other modules which are times are needed 
> >> by other applications for testing.
> >>>>>>
> >>>>>> There aren’t really too many different options we can try.
 The
> >> simplest option I can think of is just to build tez against 
> >> different versions of hadoop with the tez.version set to something 
> >> along the
> lines of
> >> “tez.version-hadoop.version”. This would imply having
> >> tez-api-0.6.0-hadoop2.4 or tez-api-0.6.0-hadoop26. For a usability
> point of
> >> view, depending on the option we pick, users will need to switch 
> >> their dependencies to point to an appropriate version based on what 
> >> version of hadoop they are using. For apps such as hive and pig, 
> >> they will need to manage picking a particular version of tez based 
> >> on which hadoop profile they are building against.
> >>>>>>
> >>>>>> Any other suggestions for publishing version dependent jars?
> >>>>>>
> >>>>>> For binary releases, should we release only the minimal 
> >>>>>> tarball? or
> >> both the minimal and full tar balls? The full tarball is the 
> >> recommended deployment model as it is more robust towards 
> >> compatibility on a
> changing
> >> cluster. It should work in most scenarios as long as the hadoop 
> >> client libraries that Tez depends on are compatible with the 
> >> servers running on the cluster.
> >>>>>>
> >>>>>> General questions for the community/past release managers:
> >>>>>> - Should we retain the simple version ( i.e. plain only x.y.z
) 
> >>>>>> when
> >> building against the default version of hadoop as determined by Tez?
> This
> >> “default.version” will have a tendency to evolve over time :) . 
> >> These simple version jars would be in addition to the version specific jars.
> >>>>>> - What versions of hadoop should we compile against? 2.2, 2.4

> >>>>>> and
> 2.6
> >> or 2.2,2.3,2.4,2.5,2.6 ? Please note that I am ignoring the minor
> version
> >> so we should pick the latest version in each line i.e. 2.2.1 over 
> >> 2.2.0
> if
> >> 2.2.1 exists.
> >>>>>>
> >>>>>> Any other comments?
> >>>>>>
> >>>>>> thanks
> >>>>>> — Hitesh
> >>>>>>
> >>>>>>
> >>>>>
> >>>>> —
> >>>>> Chris K Wensel
> >>>>> chris@wensel.net
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>
> >>> —
> >>> Chris K Wensel
> >>> chris@wensel.net
> >>>
> >>>
> >>>
> >>>
> >>
> >>
>
>
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