ci: Automatically cancel in-progress workflow runs on push

[adombeck]

Our CI jobs run for a long time and use a lot of resources.

It happens quite often to me that, after I push something to a PR, I find something to small to fix (e.g. improve the commit message) and push that fix soon after. We can save some resources by automatically cancelling in-progress workflows on new pushes to the same branch (I do that manually sometimes, but that's wasting my time).

The implementation is directly from the example of the concurrency keyword: https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#example-using-concurrency-and-the-default-behavior

[adombeck]

@denisonbarbosa @3v1n0 @didrocks What do you think about that? Should we do it in other repos too (e.g. the ubuntu-pro-for-wsl repo, which starts more than 30 jobs per workflow run)?

[didrocks]

I think this is indeed a nice one and we should standardize concurrrency across those.

I have one question as it’s unclear from the documentation: is the tag limitting concurrency on each workflow, or is it like a mutex limiting all workflows concurrent run? I think it’s per workflow (otherwise, you would have some cancellation on this PR), but just checking.

[adombeck]

is the tag limitting concurrency on each workflow, or is it like a mutex limiting all workflows concurrent run?

Which workflows are cancelled depends on the concurrency group. By defining the group as ${{ github.workflow }}-${{ github.ref }}, which, IIUC, resolves to something like qa-main, we are applying a concurrency limit on the workflow + branch name. So the QA workflow can run once per branch. If you push again, and there is already a QA workflow running for the same branch, that is being cancelled.