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From Jonathan Hung <jyhung2...@gmail.com>
Subject Re: [DISCUSS] Making 2.10 the last minor 2.x release
Date Thu, 21 Nov 2019 23:49:22 GMT
Thanks for the detailed thoughts, everyone.

Eric (Badger), my understanding is the same as yours re. minor vs patch
releases. As for putting features into minor/patch releases, if we keep the
convention of putting new features only into minor releases, my assumption
is still that it's unlikely people will want to get them into branch-2
(based on the 2.10.0 release process). For the java 11 issue, we haven't
even really removed support for java 7 in branch-2 (much less java 8), so I
feel moving to java 11 would go along with a move to branch 3. And as you
mentioned, if people really want to use java 11 on branch-2, we can always
revive branch-2. But for now I think the convenience of not needing to port
to both branch-2 and branch-2.10 (and below) outweighs the cost of
potentially needing to revive branch-2.

Jonathan Hung


On Wed, Nov 20, 2019 at 10:50 AM Eric Yang <eyang@cloudera.com> wrote:

> +1 for 2.10.x as last release for 2.x version.
>
> Software would become more compatible when more companies stress test the
> same software and making improvements in trunk.  Some may be extra caution
> on moving up the version because obligation internally to keep things
> running.  Company obligation should not be the driving force to maintain
> Hadoop branches.  There is no proper collaboration in the community when
> every name brand company maintains its own Hadoop 2.x version.  I think it
> would be more healthy for the community to reduce the branch forking and
> spend energy on trunk to harden the software.  This will give more
> confidence to move up the version than trying to fix n permutations
> breakage like Flash fixing the timeline.
>
> Apache license stated, there is no warranty of any kind for code
> contributions.  Fewer community release process should improve software
> quality when eyes are on trunk, and help steering toward the same end goals.
>
> regards,
> Eric
>
>
>
> On Tue, Nov 19, 2019 at 3:03 PM Eric Badger
> <ebadger@verizonmedia.com.invalid> wrote:
>
>> Hello all,
>>
>> Is it written anywhere what the difference is between a minor release and
>> a
>> point/dot/maintenance (I'll use "point" from here on out) release? I have
>> looked around and I can't find anything other than some compatibility
>> documentation in 2.x that has since been removed in 3.x [1] [2]. I think
>> this would help shape my opinion on whether or not to keep branch-2 alive.
>> My current understanding is that we can't really break compatibility in
>> either a minor or point release. But the only mention of the difference
>> between minor and point releases is how to deal with Stable, Evolving, and
>> Unstable tags, and how to deal with changing default configuration values.
>> So it seems like there really isn't a big official difference between the
>> two. In my mind, the functional difference between the two is that the
>> minor releases may have added features and rewrites, while the point
>> releases only have bug fixes. This might be an incorrect understanding,
>> but
>> that's what I have gathered from watching the releases over the last few
>> years. Whether or not this is a correct understanding, I think that this
>> needs to be documented somewhere, even if it is just a convention.
>>
>> Given my assumed understanding of minor vs point releases, here are the
>> pros/cons that I can think of for having a branch-2. Please add on or
>> correct me for anything you feel is missing or inadequate.
>> Pros:
>> - Features/rewrites/higher-risk patches are less likely to be put into
>> 2.10.x
>> - It is less necessary to move to 3.x
>>
>> Cons:
>> - Bug fixes are less likely to be put into 2.10.x
>> - An extra branch to maintain
>>   - Committers have an extra branch (5 vs 4 total branches) to commit
>> patches to if they should go all the way back to 2.10.x
>> - It is less necessary to move to 3.x
>>
>> So on the one hand you get added stability in fewer features being
>> committed to 2.10.x, but then on the other you get fewer bug fixes being
>> committed. In a perfect world, we wouldn't have to make this tradeoff. But
>> we don't live in a perfect world and committers will make mistakes either
>> because of lack of knowledge or simply because they made a mistake. If we
>> have a branch-2, committers will forget, not know to, or choose not to
>> (for
>> whatever reason) commit valid bug fixes back all the way to branch-2.10.
>> If
>> we don't have a branch-2, committers who want their borderline risky
>> feature in the 2.x line will err on the side of putting it into
>> branch-2.10
>> instead of proposing the creation of a branch-2. Clearly I have made quite
>> a few assumptions here based on my own experiences, so I would like to
>> hear
>> if others have similar or opposing views.
>>
>> As far as 3.x goes, to me it seems like some of the reasoning for killing
>> branch-2 is due to an effort to push the community towards 3.x. This is
>> why
>> I have added movement to 3.x as both a pro and a con. As a community
>> trying
>> to move forward, keeping as many companies on similar branches as possible
>> is a good way to make sure the code is well-tested. However, from a
>> stability point of view, moving to 3.x is still scary and being able to
>> stay on 2.x until you are comfortable to move is very nice. The 2.10.0
>> bridge release effort has been very good at making it possible for people
>> to move from 2.x in 3.x, but the diff between 2.x and 3.x is so large that
>> it is reasonable for companies to want to be extra cautious with 3.x due
>> to
>> potential performance degradation at large scale.
>>
>> A question I'm pondering is what happens when we move to Java 11 and
>> someone is still on 2.x? If they want to backport HADOOP-15338
>> <https://issues.apache.org/jira/browse/HADOOP-15338> for Java 11 support
>> to
>> 2.x, surely not everyone is going to want that (at least not immediately).
>> The 2.10 documentation states, "The JVM requirements will not change
>> across
>> point releases within the same minor release except if the JVM version
>> under question becomes unsupported" [1], so this would warrant a 2.11
>> release until Java 8 becomes unsupported (though one could argue that it
>> is
>> already unsupported since Oracle is no longer giving public Java 8
>> update).
>> If we don't keep branch-2 around now, would a Java 11 backport be the
>> catalyst for a branch-2 revival?
>>
>> Not sure if this really leads to any sort of answer from me on whether or
>> not we should keep branch-2 alive, but these are the things that I am
>> weighing in my mind. For me, the bigger problem beyond having branch-2 or
>> not is committers not being on the same page with where they should commit
>> their patches.
>>
>> Eric
>>
>> [1]
>>
>> https://hadoop.apache.org/docs/r2.10.0/hadoop-project-dist/hadoop-common/Compatibility.html
>> [2]
>>
>> https://hadoop.apache.org/docs/r3.0.0/hadoop-project-dist/hadoop-common/Compatibility.html
>>
>> On Tue, Nov 19, 2019 at 2:49 PM epayne@apache.org <epayne@apache.org>
>> wrote:
>>
>> > Hi Konstantin,
>> >
>> > Sure, I understand those concerns. On the other hand, I worry about the
>> > stability of 2.10, since we will be on it for a couple of years at
>> least.
>> > I worry
>> >  that some committers may want to put new features into a branch 2
>> release,
>> >  and without a branch-2, they will go directly into 2.10. Since we don't
>> > always
>> >  catch corner cases or performance problems for some time (usually not
>> > until
>> >  the release is deployed to a busy, 4-thousand node cluster), it may be
>> > very
>> >  difficult to back out those changes.
>> >
>> > It sounds like I'm in the minority here, so I'm not nixing the idea,
>> but I
>> > do
>> >  have these reservations.
>> >
>> > Thanks,
>> > -Eric
>> >
>> >
>> >
>> > On Tuesday, November 19, 2019, 1:04:15 AM CST, Konstantin Shvachko <
>> > shv.hadoop@gmail.com> wrote:
>> > Hi Eric,
>> >
>> > We had a long discussion on this list regarding making the 2.10 release
>> the
>> > last of branch-2 releases. We intended 2.10 as a bridge release between
>> > Hadoop 2 and 3. We may have bug-fix releases or 2.10, but 2.11 is not in
>> > the picture right now, and many people may object this idea.
>> >
>> > I understand Jonathan's proposal as an attempt to
>> > 1. eliminate confusion which branches people should commit their
>> back-ports
>> > to
>> > 2. save engineering effort committing to more branches than necessary
>> >
>> > "Branches are cheap" as our founder used to say. If we ever decide to
>> > release 2.11 we can resurrect the branch.
>> > Until then I am in favor of Jonathan's proposal +1.
>> >
>> > Thanks,
>> > --Konstantin
>> >
>> >
>> > On Mon, Nov 18, 2019 at 10:41 AM Jonathan Hung <jyhung2357@gmail.com>
>> > wrote:
>> >
>> > > Thanks Eric for the comments - regarding your concerns, I feel the
>> pros
>> > > outweigh the cons. To me, the chances of patch releases on 2.10.x are
>> > much
>> > > higher than a new 2.11 minor release. (There didn't seem to be many
>> > people
>> > > outside of our company who expressed interest in getting new features
>> to
>> > > branch-2 prior to the 2.10.0 release.) Even now, a few weeks after
>> 2.10.0
>> > > release, there's 29 patches that have gone into branch-2 and 9 in
>> > > branch-2.10, so it's already diverged quite a bit.
>> > >
>> > > In any case, we can always reverse this decision if we really need
>> to, by
>> > > recreating branch-2. But this proposal would reduce a lot of confusion
>> > IMO.
>> > >
>> > > Jonathan Hung
>> > >
>> > >
>> > > On Fri, Nov 15, 2019 at 11:41 AM epayne@apache.org <epayne@apache.org
>> >
>> > > wrote:
>> > >
>> > > > Thanks Jonathan for opening the discussion.
>> > > >
>> > > > I am not in favor of this proposal. 2.10 was very recently released,
>> > and
>> > > > moving to 2.10 will take some time for the community. It seems
>> > premature
>> > > to
>> > > > make a decision at this point that there will never be a need for
a
>> > 2.11
>> > > > release.
>> > > >
>> > > > -Eric
>> > > >
>> > > >
>> > > >  On Thursday, November 14, 2019, 8:51:59 PM CST, Jonathan Hung <
>> > > > jyhung2357@gmail.com> wrote:
>> > > >
>> > > > Hi folks,
>> > > >
>> > > > Given the release of 2.10.0, and the fact that it's intended to be
a
>> > > bridge
>> > > > release to Hadoop 3.x [1], I'm proposing we make 2.10.x the last
>> minor
>> > > > release line in branch-2. Currently, the main issue is that there's
>> > many
>> > > > fixes going into branch-2 (the theoretical 2.11.0) that's not going
>> > into
>> > > > branch-2.10 (which will become 2.10.1), so the fixes in branch-2
>> will
>> > > > likely never see the light of day unless they are backported to
>> > > > branch-2.10.
>> > > >
>> > > > To do this, I propose we:
>> > > >
>> > > >  - Delete branch-2.10
>> > > >  - Rename branch-2 to branch-2.10
>> > > >  - Set version in the new branch-2.10 to 2.10.1-SNAPSHOT
>> > > >
>> > > > This way we get all the current branch-2 fixes into the 2.10.x
>> release
>> > > > line. Then the commit chain will look like: trunk -> branch-3.2
->
>> > > > branch-3.1 -> branch-2.10 -> branch-2.9 -> branch-2.8
>> > > >
>> > > > Thoughts?
>> > > >
>> > > > Jonathan Hung
>> > > >
>> > > > [1]
>> > > https://www.mail-archive.com/yarn-dev@hadoop.apache.org/msg29479.html
>> > > >
>> > >
>> >
>> > ---------------------------------------------------------------------
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>> >
>> >
>>
>

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