Caching for Graal

[masklinn]

I'm not sure how the actions/setup-python caching is supposed to work, but every graal action indicates that it's "not found in the local cache", leading to a 30~35s overhead over cpython and pypy builds every time, contributing to the cost of graal jobs quite significantly (which adds onto graal's own issues).

[gowridurgad]

Hi @masklinn,
Thank you for the feature request. We'll investigate it and come back to you with the details!

[aparnajyothi-y]

Hello @masklinn, The actions/setup-python caching currently does not apply to GraalVM runtimes, which is why you're seeing repeated downloads and the associated overhead. Since GraalVM support was removed from hosted runners starting April 2023 (#7338), it is no longer pre-installed and must be fetched each time unless cached explicitly.

To mitigate this, you could consider:

Using setup-graalvm directly, which offers more granular control and may support caching improvements in the future.

Implementing a custom cache strategy for downloaded GraalVM builds using actions/cache.

We understand this overhead adds up, especially for CI jobs, and we’ve noted this feedback as a potential optimization area.
Please let us know in case of any further support needed

[masklinn]

Using setup-graalvm directly, which offers more granular control and may support caching improvements in the future.

It's unclear to me that setup-graalvm can set up graalpython? I tried adding it to a test workflow (mostly to see if that would work around #880) and python kept resolving to whatever the distribution had, and trying to add setup-python afterwards didn't seem to have it pick up anything.

So I don't think graalvm would help? Which makes sense, graalpython is built on graalvm but is not part of the graalvm project itself, and graalpython's own readme goes through setup-python.

[aparnajyothi-y]

Hi @masklinn, Thanks for the follow-up and for sharing your insights. You're absolutely right, setup-graalvm does not install or configure GraalPython in a way that setup-python can recognize. While GraalPython is built on GraalVM, it isn’t directly bundled with core GraalVM distributions or managed by either setup-graalvm or setup-python.

To clarify my earlier comment: the actions/setup-python caching mechanism does not apply to GraalPython or any GraalVM-based Python runtimes. Since GraalVM support was removed from GitHub-hosted runners in April 2023, it is no longer pre-installed. While setup-graalvm allows for manual GraalVM installation, setting up GraalPython still requires custom steps outside of these actions. Following further discussions with the runner-images team, there are currently no plans to add caching support for GraalPython, primarily due to memory and storage constraints on hosted runners. These limitations prevent us from pre-installing or maintaining GraalVM-related assets in the standard tool cache.

To mitigate the overhead in the meantime, you might consider:

Using setup-graalvm for manual installation of GraalVM (noting that GraalPython setup remains manual).

Implementing a custom caching layer with actions/cache to persist GraalVM and GraalPython artifacts between runs.

We recognize that repeated downloads affect CI efficiency, and while GraalPython isn’t officially supported today, your feedback is invaluable. We’ll continue monitoring demand and reassess feasibility if infrastructure constraints evolve.

Thanks again for highlighting this and for contributing.
Please feel free to reach us in case of any concerns/clarifications needed.

[masklinn]

We recognize that repeated downloads affect CI efficiency, and while GraalPython isn’t officially supported today, your feedback is invaluable. We’ll continue monitoring demand and reassess feasibility if infrastructure constraints evolve.

I'll be completely honest it's for an OSS project which only has emergencies if I do something stupid and cut a broken release, so I'm not majorly affected personally.