[openstack-dev] [all] fix latency on requirements breakage

Robert Collins robertc at robertcollins.net
Tue Nov 18 00:10:50 UTC 2014

Most production systems I know don't run with open ended dependencies.
One of our contributing issues IMO is that we have the requirements
duplicated everywhere - and then ignore them for many of our test runs
(we deliberately override the in-tree ones with global requirements).
Particularly, since the only reason unified requirements matter is for
distro packages, and they ignore our requirements files *anyway*, I'm
not sure our current aggregate system is needed in that light.

That said, making requirements be capped and auto adjust upwards would
be extremely useful IMO, but its a chunk of work;
 - we need the transitive dependencies listed, not just direct dependencies
 - we need a thing to find possible upgrades and propose bumps
 - we would need to very very actively propogate those out from global

For now I think making 'react to the situation faster and easier' is a
good thing to push on.


On 18 November 2014 12:02, Sean Dague <sean at dague.net> wrote:
> As we're dealing with the fact that testtools 1.4.0 apparently broke
> something with attribute additions to tests (needed by tempest for
> filtering), it raises an interesting problem.
> Our current policy on requirements is to leave them open ended, this
> lets us take upstream fixes. It also breaks us a lot. But our max
> version of dependencies happens with 0 code review or testing.
> However, fixing these things takes a bunch of debug, code review, and
> test time. Seen by the fact that the testtools 1.2.0 block didn't even
> manage to fully merge this weekend.
> This is an asymetric break/fix path, which I think we need a better plan
> for. If fixing is more expensive than breaking, then you'll tend to be
> in a broken state quite a bit. We really actually want the other
> asymetry if we can get it.
> There are a couple of things we could try here:
> == Cap all requirements, require code reviews to bump maximums ==
> Benefits, protected from upstream breaks.
> Down sides, requires active energy to move forward. The SQLA 0.8
> transition took forever.
> == Provide Requirements core push authority ==
> For blocks on bad versions, if we had a fast path to just merge know
> breaks, we could right ourselves quicker. It would have reasonably
> strict rules, like could only be used to block individual versions.
> Probably that should also come with sending email to the dev list any
> time such a thing happened.
> Benefits, fast to fix
> Down sides, bypasses our testing infrastructure. Though realistically
> the break bypassed it as well.
> ...
> There are probably other ways to make this more symetric. I had a grand
> vision one time of building a system that kind of automated the
> requirements bump, but have other problems I think need to be addressed
> in OpenStack.
> The reason I think it's important to come up with a better way here is
> that making our whole code gating system lock up for 12+ hrs because of
> an external dependency that we are pretty sure is the crux of our break
> becomes very discouraging for developers. They can't get their code
> merged. They can't get accurate test results. It means that once we get
> the fix done, everyone is rechecking their code, so now everyone is
> waiting extra long for valid test results. People don't realize their
> code can't pass and just keep pushing patches up consuming resources
> which means that parts of the project that could pass tests, is backed
> up behind 100% guarunteed failing parts. All in all, not a great system.
>         -Sean
> --
> Sean Dague
> http://dague.net
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Robert Collins <rbtcollins at hp.com>
Distinguished Technologist
HP Converged Cloud

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