Re: Backport Policy

[Andrew Schwartzmeyer]

I believe I fall somewhere between Alex and Ben.

As for deciding what to backport or not, I lean toward Alex's view of 
backporting as little as possible (and agree with his criteria). My 
reasoning is that all changes can have unforeseen consequences, which I 
believe is something to be actively avoided in already released 
versions. The reason for backporting patches to fix regressions is the 
same as the reason to avoid backporting as much as possible: keep 
behavior consistent (and safe) within a release. With that as the goal 
of a branch in maintenance mode, it makes sense to fix regressions, and 
make exceptions to fix CVEs and other critical/blocking issues.

As for who should decide what to backport, I lean toward Ben's view of 
the burden being on the committer. I don't think we should add more work 
for release managers, and I think the committer/shepherd obviously has 
the most understanding of the context around changes proposed for 
backport.

Here's an example of a recent bugfix which I backported: 
https://reviews.apache.org/r/67587/ (for MESOS-3790)

While normally I believe this change falls under "avoid due to 
unforeseen consequences," I made an exception as the bug was old, circa 
2015, (indicating it had been an issue for others), and was causing 
recurring failures in testing. The fix itself was very small, meaning it 
was easier to evaluate for possible side effects, so I felt a little 
safer in that regard. The effect of not having the fix was a fatal and 
undesired crash, which furthermore left troublesome side effects on the 
system (you couldn't bring the agent back up). And lastly, a dependent 
project (DC/OS) wanted it in their next bump, which necessitated 
backporting to the release they were pulling in.

I think in general we should backport only as necessary, and leave it on 
the committers to decide if backporting a particular change is 
necessary.

On 07/13/2018 12:54 am, Alex Rukletsov wrote:
This is exactly where our views differ, Ben : )

Ideally, I would like a release manager to have more ownership and less
manual work. In my imagination, a release manager has more power and
control about dates, features, backports and everything that is related 
to
"their" branch. I would also like us to back port as little as 
possible, to
simplify testing and releasing patch versions.

On Fri, Jul 13, 2018 at 1:17 AM, Benjamin Mahler <bmah...@apache.org> 
wrote:

+user, I probably it would be good to hear from users as well.

Please see the original proposal as well as Alex's proposal and let us 
know
your thoughts.

To continue the discussion from where Alex left off:

> Other bugs and significant improvements, e.g., performance, may be back
ported,
the release manager should ideally be the one who decides on this.

I'm a little puzzled by this, why is the release manager involved? As 
we
already document, backports occur when the bug is fixed, so this 
happens in
the steady state of development, not at release time. The release 
manager
only comes in at the time of the release itself, at which point all
backports have already happened and the release manager handles the 
release
process. Only blocker level issues can stop the release and while the
release manager has a strong say, we should generally agree on what
consists of a release blocking issue.

Just to clarify my workflow, I generally backport every bug fix I 
commit
that applies cleanly, right after I commit it to master (with the
exceptions I listed below).

On Thu, Jul 12, 2018 at 8:39 AM, Alex Rukletsov <a...@mesosphere.com>
wrote:

> I would like to back port as little as possible. I suggest the following
> criteria:
>
> * By default, regressions are back ported to existing release branches. A
> bug is considered a regression if the functionality is present in the
> previous minor or patch version and is not affected by the bug there.
>
> * Critical and blocker issues, e.g., a CVE, can be back ported.
>
> * Other bugs and significant improvements, e.g., performance, may be back
> ported, the release manager should ideally be the one who decides on
this.
>
> On Thu, Jul 12, 2018 at 12:25 AM, Vinod Kone <vinodk...@apache.org>
wrote:
>
> > Ben, thanks for the clarification. I'm in agreement with the points you
> > made.
> >
> > Once we have consensus, would you mind updating the doc?
> >
> > On Wed, Jul 11, 2018 at 5:15 PM Benjamin Mahler <bmah...@apache.org>
> > wrote:
> >
> > > I realized recently that we aren't all on the same page with
> backporting.
> > > We currently only document the following:
> > >
> > > "Typically the fix for an issue that is affecting supported releases
> > lands
> > > on the master branch and is then backported to the release
branch(es).
> In
> > > rare cases, the fix might directly go into a release branch without
> > landing
> > > on master (e.g., fix / issue is not applicable to master)." [1]
> > >
> > > This leaves room for interpretation about what lies outside of
> "typical".
> > > Here's the simplest way I can explain what I stick to, and I'd like
to
> > hear
> > > what others have in mind:
> > >
> > > * By default, bug fixes at any level should be backported to existing
> > > release branches if it affects those releases. Especially important:
> > > crashes, bugs in non-experimental features.
> > >
> > > * Exceptional cases that can omit backporting: difficult to backport
> > fixes
> > > (especially if the bugs are deemed of low priority), bugs in
> experimental
> > > features.
> > >
> > > * Exceptional non-bug cases that can be backported: performance
> > > improvements.
> > >
> > > I realize that there is a ton of subtlety here (even in terms of
which
> > > things are defined as bugs). But I hope we can lay down a policy that
> > gives
> > > everyone the right mindset for common cases and then discuss corner
> cases
> > > on-demand in the future.
> > >
> > > [1] http://mesos.apache.org/documentation/latest/versioning/
> > >
> >
>