Re: [PATCH] gitlab: purge msys pacman cache

[Thomas Huth <thuth@redhat.com>]

On 10/10/2025 18.05, Daniel P. Berrangé wrote:
> For the Windows msys2 CI job we install many packages using pacman
> and use the GitLab cache to preserve the pacman cache across CI
> runs. While metadata still needs downloading, this avoids pacman
> re-downloading packages from msys2 if they have not changed.
> 
> The problem is that pacman never automatically purges anything
> from its package cache. Thus the GitLab cache is growing without
> bound and packing/unpacking the cache is consuming an increasing
> amount of time in the CI job.
> 
> If we run 'pacman -Sc' /after/ installing our desired package set,
> it will purge any cached downloaded packages that are not matching
> any installed package.
> 
> This will (currently) cap the pacman download cache at approx
> 256 MB.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>   .gitlab-ci.d/windows.yml | 1 +
>   1 file changed, 1 insertion(+)
> 
> See a test job with this change, plus a find across the msys
> pacman cache, showing the cleanup effects....
> 
> Before cleanup:
> 
>    https://gitlab.com/berrange/qemu/-/jobs/11679136531#L34
> 
> After cleanup:
> 
>    https://gitlab.com/berrange/qemu/-/jobs/11679136531#L1126
> 
> diff --git a/.gitlab-ci.d/windows.yml b/.gitlab-ci.d/windows.yml
> index 1e6a01bd9a..6e1135d8b8 100644
> --- a/.gitlab-ci.d/windows.yml
> +++ b/.gitlab-ci.d/windows.yml
> @@ -87,6 +87,7 @@ msys2-64bit:
>         mingw-w64-x86_64-pkgconf
>         mingw-w64-x86_64-python
>         mingw-w64-x86_64-zstd"
> +  - .\msys64\usr\bin\bash -lc "pacman -Sc --noconfirm"
>     - Write-Output "Running build at $(Get-Date -Format u)"
>     - $env:JOBS = $(.\msys64\usr\bin\bash -lc nproc)
>     - $env:CHERE_INVOKING = 'yes'  # Preserve the current working directory

Reviewed-by: Thomas Huth <thuth@redhat.com>

I just tested this with some additional "ls -lR /var/cache/pacman" added, 
and it seems to work as expected:

  https://gitlab.com/thuth/qemu/-/jobs/11680562487#L293

This just removed an old "mingw-w64-x86_64-python-3.12.11-4-any.pkg.tar.zst" 
package, but kept the newer 3.12.12 package (and all other currently 
installed packages) around. Thus also:

Tested-by: Thomas Huth <thuth@redhat.com>