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From Konstantin Shvachko <shv.had...@gmail.com>
Subject Re: Looking to a Hadoop 3 release
Date Tue, 03 Mar 2015 07:04:54 GMT

Hadoop 3 seems in general like a good idea to me.
1. I did not understand if you propose to release 3.0 instead of 2.7 or in
   I think 2.7 is needed at least as a stabilization step for the 2.x line.

2. If Hadoop 3 and 2.x are meant to exist together, we run a risk to
manifest split-brain behavior again, as we had with hadoop-1, hadoop-2 and
other versions. If that somehow beneficial for commercial vendors, which I
don't see how, for the community it was proven to be very disruptive. Would
be really good to avoid it this time.

3. Could we release Hadoop 3 directly from trunk? With a proper feature
freeze in advance. Current trunk is in the best working condition I've seen
in years - much better, than when hadoop-2 was coming to life. It could
make a good alpha.
I believe we can start planning 3.0 from trunk right after 2.7 is out.


On Mon, Mar 2, 2015 at 3:19 PM, Andrew Wang <andrew.wang@cloudera.com>

> Hi devs,
> It's been a year and a half since 2.x went GA, and I think we're about due
> for a 3.x release.
> Notably, there are two incompatible changes I'd like to call out, that will
> have a tremendous positive impact for our users.
> First, classpath isolation being done at HADOOP-11656, which has been a
> long-standing request from many downstreams and Hadoop users.
> Second, bumping the source and target JDK version to JDK8 (related to
> HADOOP-11090), which is important since JDK7 is EOL in April 2015 (two
> months from now). In the past, we've had issues with our dependencies
> discontinuing support for old JDKs, so this will future-proof us.
> Between the two, we'll also have quite an opportunity to clean up and
> upgrade our dependencies, another common user and developer request.
> I'd like to propose that we start rolling a series of monthly-ish series of
> 3.0 alpha releases ASAP, with myself volunteering to take on the RM and
> other cat herding responsibilities. There are already quite a few changes
> slated for 3.0 besides the above (for instance the shell script rewrite) so
> there's already value in a 3.0 alpha, and the more time we give downstreams
> to integrate, the better.
> This opens up discussion about inclusion of other changes, but I'm hoping
> to freeze incompatible changes after maybe two alphas, do a beta (with no
> further incompat changes allowed), and then finally a 3.x GA. For those
> keeping track, that means a 3.x GA in about four months.
> I would also like to stress though that this is not intended to be a big
> bang release. For instance, it would be great if we could maintain wire
> compatibility between 2.x and 3.x, so rolling upgrades work. Keeping
> branch-2 and branch-3 similar also makes backports easier, since we're
> likely maintaining 2.x for a while yet.
> Please let me know any comments / concerns related to the above. If people
> are friendly to the idea, I'd like to cut a branch-3 and start working on
> the first alpha.
> Best,
> Andrew

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