When you are using downstream pipelines in Gitlab CI for complex Maven Projects as I do, you may have stumbled accross this error at least once: Cannot create local repository at: /.m2/repository. The Gitlab runner tries to create a local Maven repository at /.m2/repository – so in the topmost directory – and fails horribly due to an obvious lack of permissions. Let‘ see what happens here.
The Gitlab CI Setup
In my case I had a shell-based Gitlab runner that executes a test suite based on a few artifacts published by a Docker runner. Due to versioning and system test level realism reasons I was not able to use the artifacts directly. Unfortunate, but it shouldn’t pose that kind of a problem, does it?
Now when it comes to cloning the test suite on my shell runner, this cryptic error has been dropped. And naturally I was like „WTF is this runner trying to do!?“
The root cause in Gitlab CI downstream jobs
What I was not aware of is that per default the „child job“ inherits all the custom and Gitlab-provided runner variables from the triggering parent job that is still executed on a Docker runner. Now since the trigger happens from a Docker runner job, the variables my child job receives are poison for a baremetal environment that is my shell runner. Not least because things actually do happen at / in a Docker-based Gitlab execution environment, which is perfectly fine, but not on a shell runner.
The solution: What I had to do to make the CI jobs work
To fix the problem I had to set this on my trigger job definition:
inherit:
variables: falseThis did not just fix the error for me, but it also made perfect sense. Due to the different execution environments – shell vs. docker and project A vs. project B – I have a different set of requirements for my Gitlab CI test job. Therefore we have another case of an error leading to better software design. In addition I learned another piece of Gitlab’s sometimes quite obscure default settings.
Conclusion
I hope this helps you during your day to day journey through the jungle that are Gitlab CI downstream jobs. As I’m an avid QA engineer, so if you want to read more about writing actual automated tests. Also I take care of deeper coding basics like working with threads in java. If you’d rather want to read up about Gitlab CI’s inherit keyword, here’s the link to the relevant section of the official Gitlab CI documentation. Feel free to have a look!
Have a great weekend everybody!
