Simple trick to save environment and money when using GitHub Actions

We recently onboarded Nikita Sivukhin as a new member of our Engineering team at Turso. He immediately started to have meaningful contributions to our Native Vector Search but something else triggered me to write this article. In addition to working on his main task, Nikita started to poke around our codebase and to fix anything he found worth tackling. This is a great proactive approach which I highly recommend to any software engineer. One thing improved by Nikita was our GitHub Actions setup to avoid running jobs that are no longer needed. This is great because GitHub Actions not only consume electricity when they run but also either cost money when used for private repositories or have some usage quota for open source projects.

#What's the problem

We use GitHub Actions for our CI/CD at Turso. Both on open source projects and the ones that are private. Among other things, we run GitHub Actions on our Pull Requests. Some of those actions are pretty heavy and can take considerable amount of time. Rust compilation has its share but we also run all sorts of tests spanning from unit tests to end-to-end tests. It isn't uncommon for Pull Request to be updated before CI/CD is finished for the previous version. Unfortunately, GitHub does not cancel GitHub Actions for a stale version of the code and those tasks keep running until they either fail or fully finish. This is a problem because those old runs of CI/CD consume resources like electricity and GitHub Action runners even though no one is interested in the outcome of the run any more.

#Solution

This problem can be easily solved in a universal way. If you're running your GitHub Actions on pull_request: target then you just need to add the following snipped to the definition of your GitHub workflow:

concurrency:
  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
  cancel-in-progress: true

And voilà, GitHub will start to cancel all old GitHub Actions runs that are stale after a new version of the Pull Request was uploaded. You can see the solution in wider context in Nikita's Pull Request that added this to LibSQL GitHub repository.

#Effects

As a consequence of this change you will start seeing new result type in your GitHub Actions summary page. There will be not only green circle with a tick and red circle with an X but also a grey octagon with an exclamation point that means a task was cancelled. Below is a screenshot from GitHub Actions summary page of LibSQL repository

During the first week after Nikita's Pull Request had been merged, 56 tasks were cancelled in LibSQL repository alone.

#Conclusion

I hope that this short article was able to convince you that if you're using GitHub Actions for your CI/CD then you can easily become more environment friendly and possibly save some money on GitHub bills.