running spin plugin update concurrently trigger git clone errors

[rajatjindal]

i am running some spin tests concurrently, and as part of it I run spin plugin update

while doing so, I am running into following error:

Error cloning Git repo https://github.com/fermyon/spin-plugins/: fatal: destination path '/home/runner/.local/share/spin/plugins/.spin-plugins' already exists and is not an empty directory.

While I understand this may be out of scope for supporting in spin as such, I wanted to create the issue here to collect your feedback on this.

[itowlson]

There seems to be a dearth of cross-platform cross-process synchronisation tools. Windows has the mutex, but Unix seems to lack anything at the OS level. There is a Rust crate dir-lock (https://docs.rs/dir-lock/latest/dir_lock/struct.DirLock.html) which uses a filesystem directory as a mutex, but it's a bit kludgy, and if cleanup failed then the user would be locked out of installing plugins, so I'm a bit wary of that.

Another possibility would be to do what templates do and do the git clone to a temporary directory, then copy the content to the actual directory. This is still not robust against concurrency though.

[rajatjindal]

to be fair, i am running into this only because i am running e2e-tests which runs concurrently.

I am not sure if an enduser would run the plugin install command concurrently (at least not until we reach 100's of plugins, and someone tries to setup all of them).

i have implemented a workaround on tests side (by using file system based lock), so feel free to close the issue if you are inclined towards that.