Hey!

Around 2 months ago, bordeaux.guix.gnu.org came in to existence [1][2].

1: https://guix.gnu.org/en/blog/2021/substitutes-now-also-available-from-bordeauxguixgnuorg/
2: https://lists.gnu.org/archive/html/guix-devel/2021-06/msg00044.html

This took work I'd done on providing substitutes back in 2020 and
attempted to bring benefits from that to normal users of Guix.

Unfortunately, I don't really know if this has been much of a
success. While it should be possible to track requests for substitutes
to roughly see if anyone is making use of them, this is something I
haven't been doing yet.

In terms of the substitute availability stats, I think it's delivered
the expected benefits. I recently enabled armhf-linux builds, so now
substitute availability for the following 5 architectures should be
good:

 - x86_64-linux
 - i686-linux
 - aarch64-linux
 - armhf-linux
 - powerpc64le-linux

You can use guix weather to check the stats yourself, or look at [3] for
an overview (ignore the ci.guix.gnu.org numbers, as they're not
currently up to date).

3: https://data.guix.gnu.org/repository/1/branch/master/latest-processed-revision/package-substitute-availability

There's still some issues holding substitute availability back. The Guix
Build Coordinator still has issues building things that it can't garbage
collect. The majority of the issues though are actual problems, like
broken fixed output derivations, or generally broken packages.

The next steps in my mind remain roughly the same as they were 2 months
ago:

 - It would be good to have something to provide more visibility in to
   the Guix Build Coordinator as well as the submitting of the builds

 - Supporting performant mirroring would be great, and I have some ideas
   of how to go about this

 - I did previously have some success building things for the Hurd [4],
   and it would be great to try and replicate this on
   bordeaux.guix.gnu.org

 - data.guix.gnu.org performance in processing new revisions is a
   limiting factor, so improving this would be helpful

 - Having aggregate statistics on use of substitutes (splitting out
   machines in the build farm) would be good for assessing use and
   changes in use

 - More hardware would be good for build throughput and redundancy. For
   example, there's currently only two ARM build machines linked up, and
   I host both of them.

4: https://lists.gnu.org/archive/html/guix-devel/2021-03/msg00074.html

If you're interested in getting involved, or have any comments or
questions, please just let me know!

Thanks,

Chris