llvm dev - Feb 2019 - Clarification on expectations of buildbot email notifications

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.
> I think what's important, and what we should, after this discussion
> concludes, put in the developer policy, is that the person doing the
> revert has the responsibility to do their best to help the patch author
> reproduce the problem or at least understand the bug.
>
> This can take many forms. They can link directly to an LLVM buildbot,
> which should be self-explanatory as far as reproduction goes. It can be
> an unreduced crash report. If they're nice, they can use CReduce to
make
> it smaller. But, a reverter can't just say "Revert rNNN, breaks
> $RANDOM_PROJECT on x86_64-linux-gu". If they add, "reduction
forthcoming"
> and they deliver on that promise, I think we should support that.
>
> In other words, the bar to revert should be low, so we can do it fast
> and save downstream consumers time and effort. If someone isn't making
> a good faith effort to follow up after a revert, then authors have a
> right to push back.
We have been on the wrong side of a revert where it was "this broke
us"
and then nothing. I was inclined to just re-apply the patch, but that's
my "Mr Grumpy" avatar talking. How do we address failure to conform to
the
community norms?
> I agree with Paul that we should remove the text about checking nightly
> builders. That suggestion seems a bit dated.
That was Tom Stellard, not me, but I agree with him.
--paulr

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
>> I think what's important, and what we should, after this discussion
>> concludes, put in the developer policy, is that the person doing the
>> revert has the responsibility to do their best to help the patch author
>> reproduce the problem or at least understand the bug.
>>
>> This can take many forms. They can link directly to an LLVM buildbot,
>> which should be self-explanatory as far as reproduction goes. It can be
>> an unreduced crash report. If they're nice, they can use CReduce to
make
>> it smaller. But, a reverter can't just say "Revert rNNN,
breaks
>> $RANDOM_PROJECT on x86_64-linux-gu". If they add, "reduction
forthcoming"
>> and they deliver on that promise, I think we should support that.
>>
>> In other words, the bar to revert should be low, so we can do it fast
>> and save downstream consumers time and effort. If someone isn't
making
>> a good faith effort to follow up after a revert, then authors have a
>> right to push back.
> 
> We have been on the wrong side of a revert where it was "this broke
us"
> and then nothing. I was inclined to just re-apply the patch, but that's
> my "Mr Grumpy" avatar talking. How do we address failure to
conform to the
> community norms?
> 
>> I agree with Paul that we should remove the text about checking nightly
>> builders. That suggestion seems a bit dated.
> 
> That was Tom Stellard, not me, but I agree with him.
> --paulr
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>

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.

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
>
> >> I think what's important, and what we should, after this
discussion
> >> concludes, put in the developer policy, is that the person doing
the
> >> revert has the responsibility to do their best to help the patch
author
> >> reproduce the problem or at least understand the bug.
> >>
> >> This can take many forms. They can link directly to an LLVM
buildbot,
> >> which should be self-explanatory as far as reproduction goes. It
can be
> >> an unreduced crash report. If they're nice, they can use
CReduce to make
> >> it smaller. But, a reverter can't just say "Revert rNNN,
breaks
> >> $RANDOM_PROJECT on x86_64-linux-gu". If they add,
"reduction
> forthcoming"
> >> and they deliver on that promise, I think we should support that.
> >>
> >> In other words, the bar to revert should be low, so we can do it
fast
> >> and save downstream consumers time and effort. If someone
isn't making
> >> a good faith effort to follow up after a revert, then authors have
a
> >> right to push back.
> >
> > We have been on the wrong side of a revert where it was "this
broke us"
> > and then nothing. I was inclined to just re-apply the patch, but
that's
> > my "Mr Grumpy" avatar talking. How do we address failure to
conform to
> the
> > community norms?
> >
> >> I agree with Paul that we should remove the text about checking
nightly
> >> builders. That suggestion seems a bit dated.
> >
> > That was Tom Stellard, not me, but I agree with him.
> > --paulr
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> >
>
>
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