Mathieu Othacehe <othacehe@gnu.org> writes:

> Hello Chris,
>
>> +  guix_substitute_urls="https://ci.guix.gnu.org https://bayfront.guix.gnu.org"
>
> What is the rationale behind adding a new substitution server? I feel
> like having two substitute servers will make things more complex in term
> of maintenance.
>
> Having both servers compute the same set of substitutes is also not
> great from an energetic and resource saving point of view.

Hey,

I should have probably written a cover letter, but this patch is me
starting to try and work out the changes involved in getting substitutes
from bayfront to general Guix users, but the discussion has been
happening in this thread [1].

1: https://lists.gnu.org/archive/html/guix-devel/2021-05/msg00241.html

Bayfront has been around for a while, and has been serving substitutes,
although I'm not sure it's provided much value to users in that time. I
hope that can change with switching to using the Guix Build Coordinator
though, that happened around a month ago, and it's slowly building
things and catching up.

I guess there's a greater need to maintain it if starts getting used by
more users, so I do think the maintenance involved is something to
consider.

Personally, I see the arguments for having multiple substitute servers
getting stronger over time. Multiple independent substitute servers
would provide more reliability than a single source, as well as enabling
things like K of N trust in substitutes [2].

2: https://lists.gnu.org/archive/html/guix-devel/2020-06/msg00179.html

In terms of energy and resources, currently there are 5 machines in use,
most of which were mostly idle before being put to use building things
for substitutes. While having them build things does use more power than
having them idle, I think the value provided, even if that's providing
exactly the same bytes as ci.guix.gnu.org, is worth the cost, for the
reasons I give above.

Thanks,

Chris