bug#63634: nar 404 leads to hard ‘guix substitute’ crash

[Ludovic Courtès]

Christopher Baines <mail@cbaines.net> skribis:

> Ludovic Courtès <ludo@gnu.org> writes:

[...]

>> So it seems that bordeaux.guix did advertise zstd at some point (and
>> that narinfo is still in cache) but no longer does.
>>
>> Chris, can you confirm?
>
> Yeah, this would have been a consequence of reducing the cache size [1].
>
> 1: 
> https://git.savannah.gnu.org/cgit/guix/maintenance.git/commit/?id=ce8d3000fda6b80c0cf3e6f8204e0ee293024e6b

As discussed on IRC, I think nar-herder should honor the TTL it
advertises for all the URLs of the narinfo (lzip, zstd, etc.) because
that’s how ‘guix substitute’ currently interprets the TTL.

Eventually it would be nice for ‘guix substitute’ to interpret the TTL
as applying to one of the URLs (not necessarily all of them), but this
kind of change takes months if not years to be widely deployed because
users rarely (if ever) update guix-daemon.

Ludo’.