Caching on self-hosted runners

[rajaie-sg]

What article on docs.github.com is affected?

https://docs.github.com/en/free-pro-team@latest/actions/learn-github-actions/migrating-from-circleci-to-github-actions#caching

What part(s) of the article would you like to see updated?

Caching

Additional information

The docs state that GitHub Actions caching is only applicable to GitHub-hosted runners. which seems to indicate we can't use caching on self-hosted runners, but I just tested caching on a self-hosted runner and it worked fine. Are the docs out of date?

[welcome]

Thanks for opening this issue. A GitHub docs team member should be by to give feedback soon. In the meantime, please check out the contributing guidelines.

[janiceilene]

@rajaie-sg Thanks for opening an issue! I don't know the answer to that question, so I'm going to triage this to have the right team take a look 👀

[antoniogamiz]

Any updates on this?

[janiceilene]

Thanks for your patience! Our small team is working our way through reviewing all of the issues and PRs ✨

[janiceilene]

👋 @rajaie-sg I've gotten some answers from our engineering team and caching only works for repos hosted on github.com.

We should update the line from GitHub Actions caching is only applicable to GitHub-hosted runners. to read GitHub Actions caching is only applicable for repositories hosted on github.com

You or anyone else is welcome to open a PR with that fix ✨

[fishpen0]

Where does the cache actually live when using self-hosted runners? Is it on the filesystem, github's servers, somewhere else? Does caching do anything useful when also using the runner in ephemeral mode?

[ethomson]

We should update the line from GitHub Actions caching is only applicable to GitHub-hosted runners. to read GitHub Actions caching is only applicable for repositories hosted on github.com

I think that a more precise statement would be that caching is only applicable for workflows running on dotcom or GHEC. (In other words, caching does not work for GitHub Enterprise Server).

Where does the cache actually live when using self-hosted runners? Is it on the filesystem, github's servers, somewhere else?

GitHub's servers.

At the moment actions/cache will only store caches on GitHub itself; this is true whether your runner is self-hosted or GitHub-hosted. Obviously the question about whether this makes sense for your self-hosted runners, network-wise, is an important one. If you're caching computed data then it's probably a win! If you're caching to avoid network cost, then it may be that your cache restore is almost as expensive as running npm install.

Does caching do anything useful when also using the runner in ephemeral mode?

No, it's no different than using static self-hosted runners.

[OmgImAlexis]

At the moment actions/cache will only store caches on GitHub itself; this is true whether your runner is self-hosted or GitHub-hosted. Obviously the question about whether this makes sense for your self-hosted runners, network-wise, is an important one. If you're caching computed data then it's probably a win! If you're caching to avoid network cost, then it may be that your cache restore is almost as expensive as running npm install.

Can you please explain how this makes any sense at all to upload/download the data from github each time? Guessing this explains this...

[OmgImAlexis]

This should be reopened.

[janiceilene]

👋 @OmgImAlexis The best place to send your feedback is to https://github.com/github/feedback/discussions 💛

[OmgImAlexis]

👋 @OmgImAlexis The best place to send your feedback is to https://github.com/github/feedback/discussions 💛

Your link is broken btw. Managed to include the emoji in the link.

I've created a discussion for this as asked community/community#18549

[janiceilene]

🙈 Thanks for letting me know!

[ramonfritsch]

Just found out that you can use MasterworksIO/action-local-cache@1.0.0 for this. It just like actions/cache but runs entirely local, very suitable for self hosted instances.