bug#24496: offloading should fall back to local build after n tries

[Ludovic Courtès]

Hello!

ng0 <address@hidden> skribis:

> When I forgot that my build machine is offline and I did not pass
> --no-build-hook, the offloading keeps trying forever until I had to
> cancel the build, boot the build-machine and started the build again.
>
> A solution could be a config option or default behavior which after
> failing to offload for n times gives up and uses the local builder.
>
> Is this desired at all? Setups like hydra could get problems, but for
> small setups with the same architecture there could be a solution beyond
> --no-build-hook?

Like you say, on Hydra-style setup this could be a problem: the
front-end machine may have --max-jobs=0, meaning that it cannot perform
builds on its own.

So I guess we would need a command-line option to select a different
behavior.  I’m not sure how to do that because ‘guix offload’ is
“hidden” behind ‘guix-daemon’, so there’s no obvious place for such an
option.

In the meantime, you could also hack up your machines.scm: it would
return a list where unreachable machines have been filtered out.

Ludo’.