bug#33378: offload: Avoid hosts with little or no free disk space

[Mark H Weaver <mhw@netris.org>]

Hi Ludovic,

Ludovic Courtès <ludo@gnu.org> writes:

> ludo@gnu.org (Ludovic Courtès) skribis:
>
>> ‘choose-build-machine’ in (guix scripts offload) could/should exclude
>> build machines that don’t have at least, say, 100 MiB available in their
>> store.  That would avoid ENOSPC build failures such as
>> <https://berlin.guixsd.org/log/0hvhrfdjwnmdm2rdf58knshbbikm4ryv-r-bsgenome-hsapiens-ucsc-hg19-masked-1.3.99>.
>
> Done in commit 63b0c3eaccdf1816b419632cd7fe721934d2eb27.

Many builds require more free space than 100 MB, so this is only a
partial solution.  Also, if multiple builds are happening on the same
machine, the amount of free space available for each build will be less
than 100 MB.

Finally, the other related commit that attempts to detect build failures
caused by ENOSPC by checking if there's at least 10 MB free after the
failure won't often work in practice, I suspect.  The problem is, by the
time you perform that check, the build directory has already been
deleted.

       Mark