This changes the behaviour though: in those 10 minutes, no other builds will run, even if for most builds waiting for the update does not actually matter.

We are building lots of applications that pull in libraries that have been build by JDG. If we wouldn't run apt-get update on the cowbuilder environment we would potentially build against old versions of our libraries which I consider wrong. This actually has practical relevance since in our case the repo job of the library triggers the source job of the application.

It is my understanding that apt-get update runs anyway, but /in/ the COW instance for this build. The lock is about the general chroot, where updating should only update the minimal Debian image.

On our cluster it seems like apt-get update does not run as part of the cowbuilder_run (I guess I should see that in the build log, right?) - that's why we ran into this issue in the first place. Can you give me a hint how to enable this behavior?