Two jobs at once on denx-vulcan?

[Tom Rini]

On Fri, Sep 24, 2021 at 04:01:21PM +0200, Harald Seiler wrote:
> Hi Simon,
> 
> On Mon, 2021-09-20 at 08:06 -0600, Simon Glass wrote:
> > Hi Harald,
> > 
> > On Mon, 20 Sept 2021 at 02:12, Harald Seiler <hws at denx.de> wrote:
> > > 
> > > Hi,
> > > 
> > > On Sat, 2021-09-18 at 10:37 -0600, Simon Glass wrote:
> > > > Hi,
> > > > 
> > > > Is there something screwy with this? It seems that denx-vulcan does
> > > > two builds at once?
> > > > 
> > > > https://source.denx.de/u-boot/custodians/u-boot-dm/-/jobs/323540
> > > 
> > > Hm, I did some changes to the vulcan runner which might have caused
> > > this... But still, even if it is running multiple jobs in parallel, they
> > > should still be isolated, so how does this lead to a build failure?
> > 
> > I'm not sure that it does, but I do see this at the above link:
> > 
> > Error: Unable to create
> > '/builds/u-boot/custodians/u-boot-dm/.git/logs/HEAD.lock': File
> > exists.
> 
> This is super strange... Each build should be running in its own
> container so there should never be a way for such a race to occur.  No
> clue what is going on here...

I know this from having to track down a different oddball failure with
konsulko-bootbake.  It comes down to something along the lines of
volumes being re-used.  Good in that it means that every job every time
isn't doing a whole clone of the u-boot tree.  Bad in that just in case
the job gets wedged/killed in a crazy spot you end up with problems like
this.  If you run a 'find' on vulcan you'll figure out which overlay has
a problem.  Or you can stop the runner for a moment and tell docker to
purge unused volumes and it'll clear it up.

> > Re doing multiple builds, have you set it up so it doesn't take on the
> > very large builds? I would love to enable multiple builds for the qemu
> > steps since they mostly use a single CPU, but am not sure how to do
> > it.
> 
> Actually, this was more a mistake than an intentional change.  I updated
> the runner on vulcan to also take jobs for some other repos and wanted
> those jobs to run in parallel.  It looks like I just forgot setting the
> `limit = 1` option for the U-Boot runner.
> 
> Now, I think doing what you suggest is possible.  We need to tag build
> and "test" jobs differently and then define multiple runners with
> different limits.  E.g. in `.gitlab-ci.yml`:
> 
> 	build all 32bit ARM platforms:
> 	  stage: world build
> 	  tags:
> 	    - build
> 
> 	cppcheck:
> 	  stage: testsuites
> 	  tags:
> 	    - test
> 
> And then define two runners in `/etc/gitlab-runner/config.toml`:
> 
> 	concurrent = 4
> 
> 	[[runners]]
> 	  name = "u-boot builder on vulcan"
> 	  limit = 1
> 	  ...
> 
> 	[[runners]]
> 	  name = "u-boot tester on vulcan"
> 	  limit = 4
> 	  ...
> 
> and during registration they get the `build` and `test` tags
> respectively.  This would allow running (in this example) up to 4 test
> jobs concurrently, but only ever one large build job at once.

Yes, but this would also make it harder for people to use the CI as-is
with their own runners.  For example, the only thing stopping people
from using the free gitlab CI runners on their own is that squashfs
test being broken.

-- 
Tom
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