Re: Tooling for branch workflows

[Christopher Baines]

Andreas Enge <andreas@enge.fr> writes:

> the title says it all, I wish to share some conclusions from working on
> the core-updates merge. Clearly our tooling could be improved for the task;
> there was some flying by night without instruments, and in the end I
> merged the branch without being really able to tell how it compared
> to master... (You may also blame it partially on my lack of patience.)
> Having feature branches may or may not make things a bit easier, but it
> will definitely not solve the problems.
> This mail is also of course a bit politically sensitive: It may look like
> I am complaining about other people's work, who are volunteers and do what
> they can, without offering to work on the code myself. So as a preamble,
> let me express my gratitude to the few people who have been working
> tirelessly on our tooling and contributing to our infrastructure, without
> whom big code changes like we did on core-updates (and now on feature
> branches) would simply be impossible; their work is vital to the project
> and often not very visible. If I am critical, it is not to diminish their
> work, but to discuss about a positive path forward; and I hope more people
> will find the motivation to do infrastructure work, which I think will be
> decisive for the success of Guix (together with policy and organisational
> questions).

I too would like to see improved tooling for managing changes. I've been
working on the qa-frontpage for smaller changes, but I think this can be
extended to large changes too.

> We have two build farms, berlin and bordeaux (which is a good thing for
> checking reproducibility and for redundancy, but maybe a bit of a problem
> concerning hardware requirements for "exotic" architectures), running
> two different CI projects, cuirass and the Guix build coordinator (gbc in
> the following); both have a very low bus factor (1 to 2?), and it would be
> nice to get more people onboard. For this, more documentation would be
> helpful. Both have pros and cons, and are architectured quite differently,
> so I do not know whether convergence is achievable.

This is something I'd like to see too. I've been thinking about this
already and want to spend more time working on at least making it easier
for more people to get involved. Let me know if you have any specific
requests!

> I ended up relying mostly on cuirass for reasons I do not completely
> remember any more. The dashboard with its green and red dots is a very
> useful tool compared to lists of builds, which become unusable with over
> 20000 packages. The bigger build power on bordeaux is helpful, and I found
> the web interface of gbc a bit slow and down a bit too often. With this
> experience, I just filed three wishlist bugs for cuirass:
> - Topological sorting in cuirass
>   https://issues.guix.gnu.org/63412
>   The lack of ordering the builds is a big problem wasting a lot of build
>   power; it is solved in gbc and, I think, the reason why the bordeaux
>   build farm fares better for aarch64 with fewer machines.
>   I would tag this as "important".
> - Evaluation comparison on cuirass
>   https://issues.guix.gnu.org/63414
>   Without being able to compare a branch to master, it is difficult to
>   decide whether one should merge. This is sort of solved in gbc, but so
>   far the bordeaux build farm has been used more for QA of single patches
>   (or a short list of patches featuring in a single issue) than for building
>   complete branches.
> - Stop and restart builds in cuirass
>   https://issues.guix.gnu.org/63413
>   Manual intervention is not easy in cuirass (I spent hours clicking on
>   "restart" or using the REST API with a shell script through wget, which
>   resulted in my IP being banned as a DoS suspect...); and to my knowledge,
>   there is no web interface for doing so in gbc. In both systems one can
>   probably tinker with the underlying databases, but this also does not
>   qualify as "easy".

There's intentionally no concept of restarting builds in the build
coordinator, however unlike Cuirass, it does support having multiple
builds for the same derivation.

So, to try to build something again you just submit another build for
the derivation, which can be as simple as running this on bayfront:

  guix-build-coordinator build /gnu/store/foo.drv

Having to have SSH access to bayfront to do this isn't ideal though, so
we can expose some kind of authenticated interface to do this, maybe
through the new bffe or the qa-frontpage.

Thanks,

Chris

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