> On Mar 12, 2018, at 4:59 AM, Adi Roiban <a...@roiban.ro> wrote:
> 
> Hi,
> 
> It is not clear to me what builders need to pass before we can merge 
> something.
> 
> I expect that all supported "platforms" need to pass, but it is not
> clear what are the currently supported platforms.
> 
> We have this info in the wiki but it does not help.
> https://twistedmatrix.com/trac/wiki/ReviewProcess#Authors:Howtomergethechangetotrunk
> 
> In GitHub I can see Travis / Appveyor and OSX from Buildot as "Required"

These are marked as "required" because they're necessary, but not sufficient.

> Is that all?

Ideally all the supported buildbots should be passing.  It's a real shame that 
the offline buildbots do not report any status, because it makes it very easy 
to miss them.  (I personally did not realize the ramifications of the way 
buildbot repots status until I looked at 
https://buildbot.twistedmatrix.com/boxes-all?branch=trunk&num_builds=10 
<https://buildbot.twistedmatrix.com/boxes-all?branch=trunk&num_builds=10> just 
now).

> If I check the "supported" group in Buildbot, I see many more builders.
> The problem is that a significant number of slaves are down and those
> builders are not available.

So, normally I'd say, like Jean-Paul did, that we should just get in touch with 
the maintainers of the buildbots in question.

But it seems the buildbots in question were the ones we had running on our 
donated Rackspace Cloud account.

Logging into the control panel for that account, literally all the servers 
except for the buildmaster (i.e. buildbot.twistedmatrix.com 
<http://buildbot.twistedmatrix.com/>) have been deleted.  Not just shut down, 
but, completely gone.  This is baffling to me.  I do not know who could have 
done this or why.  There does not appear to be an audit log I can consult.  
Based on billing data, and consistent with the buildbot logs, it appears that 
this occurred some time in early January.

> Is Fedora still supported and required?

That's the hope.  Those buildbots appear to be online.

> I suggest to use GitHub "Required" marker to document what platforms are 
> supported.

I want to agree with you.  However, our tests are not reliable or performant 
enough for this.

The "required" marker makes it impossible to merge changes without a passing 
status or an administrator override.  This has an unfortunate set of 
corollaries.  Assuming a non-administrator reviewer:

If a single builder has a temporary configuration issue and you're not an 
administrator, you can't merge any code.
Let's say the probably of an intermittent test failing is 50 to 1.  A 2% 
chance.  The probability of a test suite passing is 98%.  We have 36 supported 
builders.  The probability of all the builders passing for a successful run is 
then just 13%; roughly 1 in 10 valid branches will be able to land. (I think 
our probability is actually quite a bit better than this these days, but you 
get my drift.)
Even if a contributor can force all the builds to re-run (which requires 
special permissions, and thus needs to wait for a project member) getting a 
successful run on every builder could require 2 or 3 tries, which could be 2 or 
3 hours of waiting just to get one successful run on a platform that you know 
is not relevant to the change you're testing.

Therefore keeping a small core set of "most pass" statuses and allowing for 
some human judgement about the rest is a practical necessity given the level of 
compute resources available to us.

> We don't have time to maintain the infrastructure, so I suggest to
> drop support for anything that is not supported by Travis and
> Appveyor.

My preference would be to simply drop all the buildbots which have been (for 
some reason) destroyed from the supported build matrix, since the buildbots are 
still covering a multiplicity of kernels and environments that travis and 
appveyor aren't.  But, I don't have the time to do much more than write this 
email, so if we have no other volunteers for maintenance, I will support your 
decision to tear down the buildbots for now.

Jean-Paul recently pointed out that CircleCI has much more performant macOS 
builds than Travis, so if someone were motivated to make that change but didn't 
want to keep maintaining hardware, that might be one way to go.

> I know that this might be disruptive.
> I think that we need it in order to raise awareness that supporting a
> platform is not easy.

I do hope that this will provoke some potential volunteers to come forward to 
help maintain our failing infrastructure.

> If someone (including me) cares about a platform they should find a way to 
> help to project supporting that platform.

> What do you think?

I do hope that if you're going to make a change, you'll consider something 
slightly less drastic than blowing up the buildbots entirely :).  But with a 
dozen servers having just disappeared with no explanation, it's a course of 
action which at least makes sense.

-g

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