[cfe-dev] [Openmp-dev] RFC: Release process changes

[Tom Stellard via cfe-dev]

On 05/25/2020 05:48 AM, Hans Wennborg wrote:
> On Thu, May 21, 2020 at 8:59 PM Tom Stellard via Openmp-dev
> <openmp-dev at lists.llvm.org> wrote:
>>
>> Hi,
>>
>> I would like to propose a few changes to the LLVM release process.  The
>> current process is documented here:  https://llvm.org/docs/HowToReleaseLLVM.html
>>
>> There are two parts to this proposal.  The first is a list of clarifications,
>> which are things we are currently doing that aren't documented. The second
>> is a list of changes which would actually modify how releases are currently
>> managed.
>>
>>
>>
>> *** Proposed Clarifications ***
>>
>>
>>
>> **  Release manager is allowed to commit changes to the release branch without
>>     code owner approval.  However, the release manager is encouraged to consult
>>     with code owners or patch reviewers for non-trivial changes.
>>
>> It's not practical to get code owner approval every time.  Either because there
>> is no code owner or because the number of backports is too high (e.g. pre-rc1 / pre-rc2).
>> This proposed clarification matches how releases are currently managed.
> 
> +1
> 
> Maybe even stronger than "is allowed to commit", I think we should
> really think about it as the release manager owning the branch, and
> has full authority over what goes into it or not. Consulting code
> owners often makes sense of course, but for many patches, consulting
> the code owner (when there is one) is an unnecessary slowdown.
> 
>> ** There is no official release criteria.
>>
>> We have time-based releases and when the release is 'ready' has been
>> up to the discretion of the release manager.  Changing the release
>> criteria is out of the scope of this proposal, but I do think it would
>> be good to have a discussion about this as a community, so I'm going to
>> start a separate thread to discuss this.
>>
>>
>>
>> *** Proposed Changes ***
>>
>>
>>
>> ** Create a time-based bug-fix release schedule.  After each major release, make
>>    a new bug-fix release every 2 weeks for 12 weeks (6 releases total).
>>
>> ** Eliminate release candidates for bug-fix releases.
>>
>> The current unofficial bug-fix release schedule is:
>>
>> X.Y.1-rc1 (6 weeks after major release)
>> X.Y.1-rc2 (10 weeks after major release)
>> X.Y.1-final (12 weeks after major release)
>>
>> I think this change will improve the overall test coverage of the release branch.
>> I don't think the branch itself or even the release candidates get the same
>> level of testing as the final releases.  If we are consistently snapshotting
>> the release branch and putting out releases, I think this will make it easier
>> and thus more likely that users will test out the release branch code.
>>
>> Additionally, with more frequent bug-fix release it removes the need to have
>> release candidate releases. Every bug-fix release (up until the last one)
>> would serve the same purpose as our current release candidates in that they
>> are intended to give users an easier way to test the code before the final
>> release.
> 
> My first thought is that doing all these releases sounds like a lot of
> work. Would you be doing all of them, or would there be some other
> arrangement? I suppose if we release this often, and also skip the
> RCs, we might become more efficient at it :-)
> 

Yes, I would plan to do all the releases.  For 9.0.1, there were
3 RCs, so 4 releases in total.  Doing 6 instead of 4 is not that much
more work in my opinion.  Also, we may end up skipping releases if
there aren't any new changes in the branch.  But doing extra
releases would be good motivation to try to automates more parts of the
release process.

If we do feel like 6 is too many we could lengthen the interval to 3 weeks,
which would give us just 4 releases.

> Secondly, is having this many releases useful for downstream? One
> concern might be that downstream consumers just wait for the .6 one,
> and then there's no benefit and also no extra testing of the branch.
> Is it mainly increasing test coverage of the branch that's the
> motivation, or is it the demand for more bug-fix releases?
> 

>From me as a distro package maintainer, I'm more likely to package
a final release than a bug-fix release.  Especially if I know there won't
be another release candidate or final release coming very soon after.

Besides increasing testing coverage, I think it helps other projects
avoid having to do things like this: https://lkml.org/lkml/2020/5/5/1446
In this case, the kernel release cycle is about 2 months, so they can't
wait 3 months for a fix.


> Not having at least one release candidate sounds a bit scary to be.
> Without them we could get into a situation where everything works fine
> on the release manager's machines, but is completely broken on other
> platforms, and no way to fix until the next dot release. Maybe that
> kind of breakage is less likely after the major release, but it still
> seems it could make these dot releases less stable?
> 

I think in order to do this we need to have a certain level of CI testing.
I've been experimenting with this in the last few release cycles.  Right now,
in the release branch we have tests running make-check for clang, llvm, lld,
libclc, and running make for lldb.  Each test runs on Linux, Mac, and Windows.
I feel comfortable enough with this that it would catch most obvious issues
with new bug-fix releases.  Especially since the number of changes is low
as compared to major releases.

I think there would need to be some flexibility to do another bug-fix release
ASAP if there is a major problem.  

-Tom

>> ** Create clear rules for what kind of backports are accepted during each
>>    release phase.
>>
>> * Before RC1:Patches should be limited to bug fixes, important optimization
>>   improvements, or completion of features that were started before the branch
>>   was created.  As with all phases, release managers and code owners can reject
>>   patches that are deemed too invasive.
>>
>> * Before RC2: Patches should be limited to bug fixes or backend specific
>>   improvements that are determined to be very safe.
>>
>> * Before RC3/Final: Major Release* Patches should be limited to critical
>>   bugs or regressions.
>>
>> * Bug fix releases: Patches should be limited to bug fixes or very safe
>>   and critical performance improvements.  Patches must maintain both API and
>>   ABI compatibility with the previous major release.
>>
>> * Final bug fix release: Patches should be limited to critical bug fixes only.
> 
> These sound good to me.
> 
> 
> Thanks,
> Hans
>