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

[Ludovic Courtès]

Hi!

zimoun <zimon.toutoune@gmail.com> skribis:

> I am just hitting this old bug#24496 [1].
>
> On Mon, 26 Sep 2016 at 18:20, ludo@gnu.org (Ludovic Courtès) wrote:
>> ng0 <ngillmann@runbox.com> 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.
>
> [...]
>
>> 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.
>
> When the build machine used to offload is offline and the master daemon
> is --max-jobs=0, I expect X tries (leading to timeout) and then just
> fails with a hint, where X is defined by user.  WDYT?
>
>
>> In the meantime, you could also hack up your machines.scm: it would
>> return a list where unreachable machines have been filtered out.
>
> Maybe, this could be done by “guix offload”.

Prior to commit efbf5fdd01817ea75de369e3dd2761a85f8f7dd5, this was the
case: an unreachable machine would have ‘machine-load’ return +inf.0,
and so it would be discarded from the list of candidates.

However, I think this behavior was unintentionally lost in
efbf5fdd01817ea75de369e3dd2761a85f8f7dd5.  Maxim, WDYT?

Thanks,
Ludo’.