[bug#27876] [PATCH] cuirass: add Hydra compatible HTTP API.

[Mathieu Othacehe <m.othacehe@gmail.com>]

Hi Ludo !

I'll submit a v2 soon, here are some answers to your remarks.

> That said, there’s only one place where we work, which is where we spawn
> the ‘evaluate’ command.  It may be that spawning it with ‘open-pipe’
> from (ice-9 popen) would sidestep the problem because ‘open-pipe’ is
> specifically written to permit this.

The open-pipe solution seems fine indeed !

> I think it would be nice to have a couple of tests for the HTTP API.
> There are helpers in tests/publish.scm and (guix tests http) that could
> probably be borrowed here.  WDYT?

Sure, I'll add some new tests on the new API.

> Anyway, awesome work!  It’s a really important gap that you’re filling
> here.

Thank you ;)

> In the future it would be nice to have an API to add jobsets, trigger an
> evaluation, things like that.  That’s probably more difficult though
> because we’ll need an authentication mechanism.
>
> Also we should consider Fiberizing the whole thing eventually, so that
> Cuirass can actually perform all its activities concurrently.

Yes my planning is the following :

1. Fiberizing the whole thing to make it scalable.
2. Add build start/stop detection : I think the ideal would be wip-ui
branch to get merged before, so that I can use the same mechanism to
parse build output :)
3. Add authentification, and the other API you're describing.

Still plenty of work !!

Mathieu