[libvirt PATCH 7/7] ci: integration.sh: Define the SCRATCH_DIR variable for local execution

[Daniel P. Berrangé]

On Mon, Jan 23, 2023 at 02:19:23PM +0100, Erik Skultety wrote:
> ...
> 
> > > Although an option, the main motivation here to remain consistent with how it
> > > works in GitLab. Since we define SCRATCH_DIR under the 'vars' section, IIRC you
> > > can only use a scalar value, not a command (if we can, I retract my argument)
> > > and hence we'd have to export and define the variable under each script,
> > > before_script, after_script sections.
> > > 
> > > So, I preferred consistency here, since I wouldn't  realistically expect an
> > > engineer to have /tmp/scratch prior to executing script given the main
> > > motivation here is to quickly get a throwaway test machine to run the script
> > > and THEN debug if the tests fail. So, while I agree you're right here, I don't
> > > think it's a likely scenario.
> > 
> > I'm wondering why I put it at /tmp/scratch in the first place when we
> > started using gitlab, and struggling to come up with a justification.
> > 
> > In fact I'm not entirely convinced we really need a SCRATCH_DIR env
> > variable at all, since AFAICT, we only use it one place for creating
> > $VROOT.
> > 
> > In terms of standalone reproduction of build env, it would be saner
> > to use VOORT=$CWD/vroot, which I think would probably work under
> > GitLab ok too, and do away with SCRATCH_DIR.
> 
> That would be just a replacement of one var for another and we'd still have to
> keep clearing/removing vroot anyway - one thing I didn't mention, because it
> was irrelevant up until this point, is that in the future we should improve the
> local experience even more by following the logic we have for local container
> envs where we mount the git directory inside the container as a volume. Using
> the same mantra, I can imagine us using e.g. virtiofs to mount the git dir to the
> VM so that the developer can run ninja build immediately without having to wait
> for gitlab and test directly with their own development branch in a safe
> environment.
> 
> The difference is that while /tmp would be cleared on VM destroy, vroot's
> content as you propose would remain as a side-effect after destroying the VM
> unless we clear it in which case it's no different to the current SCRATCH_DIR
> solution, so with this in mind I think we should keep it the way we have.

The /tmp directory is often a ram disk though, hence my aversion to
using /tmp, as you can't be confident it has sufficient space for
without impacting other aspects of the system. With $CWD/vroot you
can expect access to the full extent of the user's storage.

If we're passing through a host git checkout though, that's sketchy,
unless we did a git clone --reflink, to get a pristine checkout for
each job in an efficient way.

With regards,
Daniel
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