[llvm-dev] Clarification on expectations of buildbot email notifications

[Justin Bogner via llvm-dev]

Zachary Turner via llvm-dev <llvm-dev at lists.llvm.org> writes:
> On Wed, Feb 20, 2019 at 9:13 AM Tom Stellard <tstellar at redhat.com> wrote:
>> On 02/20/2019 07:39 AM, via llvm-dev wrote:
>> > Reid said:
>> >
>> >> I don't think whether a buildbot sends email should have anything to do
>> >> with whether we revert to green or not. Very often, developers commit
>> >> patches that cause regressions not caught by our buildbots. If the
>> >> regression is severe enough, then I think community members have the
>> >> right, and perhaps responsibility, to revert the change that caused it.
>> >> Our team maintains bots that build chrome with trunk versions of clang,
>> >> and we identify many regressions this way and end up doing many reverts
>> >> as a result. I think it's important to continue this practice so that
>> >> we don't let multiple regressions pile up.
>> >
>> > My team also has internal bots and we see breakages way more often than
>> > we'd like.  We are a bit reluctant to just go revert something, though,
>> > and typically try to engage the patch author first.
>> >
>> > Engaging the author has a couple of up-sides: it respects the author's
>> > contribution and attention to the process; and once you've had to fix
>> > a particular problem yourself (rather than someone else cleaning up
>> > after your mess) you are less likely to repeat that mistake.
>> >
>>
>> In my opinion engaging the author first is the best approach for internal
>> bots, and I think this should be captured in some way in the developer
>> guide.
>>
>> We don't want to send the message that is OK to revert patches at any
>> time just because one of your internal tests failed.  In my experience
>> most community members do engage with the author first, like Paul
>> describes,
>> so this isn't usually a problem, but new contributors may not be familiar
>> with this precedent.
>>
>> -Tom
>
> This is kind of what I was getting at with my original email, so thank you
> for wording it better than I did.
>
> If we can agree that "contact the author first for internal bots" is better
> than "revert automatically, even for internal bots" (which may not be the
> case, I don't want to speak for others), then the problem becomes one of
> defining what an "internal bot" is.  In my opinion, an internal bot it is
> one that does does not satisfy both conditions: a) on the public waterfall,
> b) automatically sends notifications, but perhaps not everyone agrees with
> this definition.

I would argue that "internal vs external" is the wrong division here.
It does come up that internal bots or weird local configurations find
significant problems in practice sometimes, and reverting to green can
be completely reasonable for these cases. Obviously some discretion is
necessary, but reverting more or less any change that causes issues
severe enough to legitimately block you or seriously hamper your ability
to notice further issues is fair game in my eyes.

Like Reid says, the important part about reverting is the contract
between the person doing the revert and the original committer. When a
patch is reverted, the reverter has a responsibility for making sure the
originator has the means to fix whatever problem they found. Any revert
that isn't tied to a public bot absolutely must come with reasonable
instructions to reproduce the problem, and the reverter needs to
actively engage with the originator to get the patch back in in a form
that doesn't hit the problem.