The issue also exists when using --with-commit - see below for a refined test that makes it trivial to demonstrate with any package where the source is retrieved from git.
> Philip Beadling <phil@beadling.co.uk> writes:
>No, and we probably should do, even in spite of this issue. We're going
>to repeat the experiment now using --with-commit, to confirm behaviour there.
Let's try and build 2 package variations - for this experiement we don't even have to run them at the same time:
mkdir checkout-test
cd checkout-test
mkdir cache1 cache2
XDG_CACHE_HOME=`realpath ./cache1` guix build --with-commit=simm=3981f60d81d3c9592d78b3e88545259713a93194 simm
XDG_CACHE_HOME=`realpath ./cache2` guix build --with-commit=simm=ec1357c1fdf78a2ac1408d00c0c3e7d025ab9ade simm
Now look at the caches:
$ ll cache1/guix/checkouts
total 4.0K
-rw-rw-r-- 1 phil.beadling phil.beadling 10 Jan 18 12:37 last-expiry-cleanup
drwxrwxr-x 6 phil.beadling phil.beadling 162 Jan 18 12:37 lx4ipn27sk6uvu6b33kelt4tik65oianvl7b7yn5bpng7gpt4pyq
drwxrwxr-x 5 phil.beadling phil.beadling 115 Jan 18 12:37 mqqlbc4ksftu2tkbnxydosm4j6mynxsh5nmhpq3cfrofkktkhexq
drwxrwxr-x 5 phil.beadling phil.beadling 103 Jan 18 12:37 qqzuuoqxvqikivkpenqom43kzk2xr7nlntanbm6fpe7bci6kaenq
drwxrwxr-x 4 phil.beadling phil.beadling 202 Jan 18 12:37 smvbhjf46cbaxxju6fsqj7t6ujktxy5i7vhuhzpvgjt2vhid2vqq
drwxrwxr-x 5 phil.beadling phil.beadling 267 Jan 18 12:37 xulvhb6agjrsf6x7wknutpn7wkt5i4nesk637czazvfxps357eoq
$ ll cache2/guix/checkouts
total 4.0K
-rw-rw-r-- 1 phil.beadling phil.beadling 10 Jan 18 12:38 last-expiry-cleanup
drwxrwxr-x 6 phil.beadling phil.beadling 162 Jan 18 12:38 lx4ipn27sk6uvu6b33kelt4tik65oianvl7b7yn5bpng7gpt4pyq
drwxrwxr-x 5 phil.beadling phil.beadling 115 Jan 18 12:38 mqqlbc4ksftu2tkbnxydosm4j6mynxsh5nmhpq3cfrofkktkhexq
drwxrwxr-x 5 phil.beadling phil.beadling 103 Jan 18 12:39 qqzuuoqxvqikivkpenqom43kzk2xr7nlntanbm6fpe7bci6kaenq
drwxrwxr-x 4 phil.beadling phil.beadling 202 Jan 18 12:38 smvbhjf46cbaxxju6fsqj7t6ujktxy5i7vhuhzpvgjt2vhid2vqq
drwxrwxr-x 5 phil.beadling phil.beadling 267 Jan 18 12:38 xulvhb6agjrsf6x7wknutpn7wkt5i4nesk637czazvfxps357eoq
$
Despite asking for different variants of the simm package, they are both stored under the same SHA. If they both used the same cache directory (the default) - they'd have overwritten each other. Thus it is not safe to run --with-commit or any other variation in parallel for the same user.
To prove I've matched the right SHA - I can back-out the original commit ids provided to --with-commit:
$ cd cache1/guix/checkouts/xulvhb6agjrsf6x7wknutpn7wkt5i4nesk637czazvfxps357eoq && git rev-parse HEAD && cd -
3981f60d81d3c9592d78b3e88545259713a93194
~/checkout-test
$ cd cache2/guix/checkouts/xulvhb6agjrsf6x7wknutpn7wkt5i4nesk637czazvfxps357eoq && git rev-parse HEAD && cd -
ec1357c1fdf78a2ac1408d00c0c3e7d025ab9ade
~/checkout-test
$
Whilst my original setup was a bit of a edge-case, I think this refined example demonstrates that the problem can occur with typical/reasonable use of guix switches? I can even think of how this could occur without the user running in parallel - for example if a package required via nth-order dependencies to build 2 versions of the same repo - it's possible that a single "guix build" command could cause the issue?
Thoughts?