bug#57559: guix pull fails on http status code 503

[zimoun <zimon.toutoune@gmail.com>]

Hi Maxime,

On Thu, 08 Sep 2022 at 11:23, Maxime Devos <maximedevos@telenet.be> wrote:

> Looking at 'latest-channel-instances', the code for deciding what the
> latest version is, is the same for the guix channel and any other
> channel.  As such, the 'Guix is unavailable' is, currently, not special.

Well, ’latest-channel-instances’ relies on ’latest-channel-instance’
which tests ’guix-channel?’,

--8<---------------cut here---------------start------------->8---
(define (guix-channel? channel)
  "Return true if CHANNEL is the 'guix' channel."
  (eq? 'guix (channel-name channel)))
--8<---------------cut here---------------end--------------->8---

then, for instance, the occurrences are:

--8<---------------cut here---------------start------------->8---
12 candidates:
./guix/channels.scm:79:            guix-channel?
./guix/channels.scm:192:(define (guix-channel? channel)
./guix/channels.scm:199:  (if (and (guix-channel? chan)
./guix/channels.scm:424:            (when (guix-channel? channel)
./guix/channels.scm:437:    (when (guix-channel? channel)
./guix/channels.scm:778:            (guix-channel? (channel-instance-channel instance)))
./guix/channels.scm:903:        (item (if (guix-channel? channel)
./guix/scripts/pull.scm:775:        (match (find guix-channel? channels)
./guix/scripts/pull.scm:788:                   (remove guix-channel? channels))))
./gnu/packages/package-management.scm:125:                                guix-channel?
./gnu/packages/package-management.scm:618:   (delay (match (or (find guix-channel? (current-channels))
./gnu/ci.scm:478:    (find guix-channel? channels))
--8<---------------cut here---------------end--------------->8---

And my point is that the Guix channel is special when pulling.
Therefore, we could split the cases when the Guix channel is unreachable
and when other extra-channels are unreachable; because the impact are
different, IMHO.

As I pointed earlier in the thread, the main issue is when these extra
channels are unreachable; as André have initially reported.


Cheers,
simon