[SRU] OpenStack Stable Snapshots

[Corey Bryant]

On Mon, Feb 22, 2021 at 5:16 PM Corey Bryant <corey.bryant at canonical.com>
wrote:

> Hello SRU Team,
>
> I'm writing to discuss delivery of patches from extended maintenance
> stable branches as snapshots.
>
> This would occur during the extended maintenance phase of an upstream
> stable branch, which falls between the maintained phase and EOL phase.
> I would see this process being similar to the current process that is used
> to deliver stable point releases, described at:
> https://wiki.ubuntu.com/OpenStack/StableReleaseUpdates.
>
> Snapshots refers to the process by which we currently deliver package
> updates during a development release and prior to the final release. For
> example, nova 3:22.0.1+git2021012713.d92c0740c6-0ubuntu1 in hirsute
> contains everything in the upstream master git branch up to commit hash
> d92c0740c6.
>
> == What is Extended Maintenance? ==
> First, it's worth understanding what the upstream "Maintained" phase is.
> During this phase, upstream regularly releases stable point releases that
> are based on a specific commit (e.g. the latest HEAD commit for the
> stable/queens branch at a point in time), and we then package those point
> releases up in distro.
>
> Following the "Maintained" phases is the "Extended Maintenance" phase.
> During this phase, upstream no longer cuts any stable point releases for
> that stable branch, however patches continue to be backported to the
> branch. This is the phase where we would like to have the ability to
> deliver snapshots of stable branches. This would allow us to pick up all
> stable branch patches since, say, the final point release for stable/queens
> (bionic). For example, the current version of nova in bionic is
> 2:17.0.13-0ubuntu1, and that is based on the final point release for
> upstream stable/queens. If we were to do a snapshot today for nova in
> bionic, it would be versioned along the lines of
> 2:17.0.13+git2021022200.944443a7b0-0ubuntu1.
>
> More details on upstream maintenance phases can be reviewed at:
> https://docs.openstack.org/project-team-guide/stable-branches.html#maintenance-phases
>
> == Advantages of Stable Snapshots ==
> * Less overhead for the OpenStack engineering and SRU teams. Currently we
> have various cherry-picked patches that are dealt with via separate SRU
> bugs requiring individual testing.
> * As the cherry-pick process is reactive, many of these SRUs tend to be
> high impact or critical for users, requiring immediate action from these
> teams.
> * We have a lot of users that are now on, and moving to, bionic (queens)
> and we would like to be more proactive in fixing bugs for them.
> * This would naturally result in a regular cadence along the lines of the
> monthly stable point release cadence that we currently follow.
> * Cherry-picking individual patches can increase regression potential for
> frequently modified code when they don't apply cleanly.
> * All patches that have landed in an extended maintenance branch have
> already landed in all ensuing stable branches and master, therefore
> negating much of the regression potential mentioned in "Disadvantages"
> below.
>
> == Disadvantages ==
> * Upstream stable branches that are in extended maintenance do not
> guarantee the same upstream test coverage that supported branches do. The
> maintenance-phases documentation states "There is no statement about the
> level of testing and upgrades from Extended Maintenance are not supported
> within the Community."
>
> == What Ubuntu Releases would this affect? ==
> Stable snapshots would only be needed for Ubuntu LTS releases (Upstream
> "Maintained" period is 18 months for stable branches). Currently this would
> only be applicable to Ubuntu 18.04 as bionic is the only LTS with a
> corresponding upstream stable branch that's in extended maintenance.
>
> == How many patches are we talking about? ==
> For a sampling of stable/queens, new snapshots would pick up this many
> patches:
>
> nova: 337
> neutron: 106
> heat: 47
> cinder: 21
> glance: 11
> designate: 11
> swift: 10
> horizon: 8
> keystone: 7
>
> A few of those look daunting, yes, but perhaps that depends on how you
> look at it. Also please keep in mind, queens has been in extended
> maintenance since October of 2019 so this would be quite the one-time
> waterfall for bionic. In the future we'd pick up fewer patches at a time at
> a regular cadence.
>
> Thanks for taking the time to read this. Please let me know if you have
> any opinions or questions about this approach.
>
> Corey
>

Hello SRU Team,

I wanted to see if I could revive this topic and discuss the possibility of
moving forward with stable snapshots as described in this thread.

Would it make sense to add this to a meeting agenda or is the mailing list
a good place to discuss?

Thank you,
Corey
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