bug#48468: substitute server connection timeout

[Mathieu Othacehe]

Hello,

> /gnu/store/qmzr030rzgikdxv3g9msqv0l8qp5j6y2-btrfs-raid-root-os.drv,
> which was marked as failed earlier today due to missing .drv.  It’s a
> 4KiB file, and the cache-bypass-threshold is ‘guix publish’ is typically
> set to something much higher than that.  So ‘guix publish’ won’t return
> 404 in that case.

Yes but that derivation also depends on other derivations, for instance
qemu-minimal and if I try:

--8<---------------cut here---------------start------------->8---
mathieu@berlin ~$ guix build qemu-minimal
...
/gnu/store/lwv2pl0m6dkf6bkzip755w5p71g5akq4-qemu-minimal-7.1.0
--8<---------------cut here---------------end--------------->8---

and then, from my machine.

--8<---------------cut here---------------start------------->8---
curl https://ci.guix.gnu.org/lwv2pl0m6dkf6bkzip755w5p71g5akq4.narinfo
We're baking it: /lwv2pl0m6dkf6bkzip755w5p71g5akq4.narinfo
--8<---------------cut here---------------end--------------->8---

wget exhibits the same behaviour and returns 404.

So any build that requires a heavy substitute, heavier than the cache
bypass threshold at least, will fail on the workers, as it would fail
locally.

That's not really a surprise as baking substitutes takes time and there
is a time window between the moment Cuirass triggers NAR baking and the
moment the NAR is baked, where every user will get a 404.

Mathieu