Our GitHub Actions cache is always full:

Approaching total cache storage limit (10.65 GB of 10 GB Used)

Least recently used caches will be automatically evicted to limit the total cache storage to 10 GB. Learn more about cache usage.

https://github.com/python/cpython/actions/caches

Right now, PR caches use up 3.54 GB across 52 PRs:

• 32 PRs are closed and using 1.81 GB
• 20 are open with 1.73 GB

They tend to get evicted after about a day due to the storage limit, and don't last the full 7-day limit.

But why are there so many caches for PRs?

Nearly all of this is pip caches from docs builds, and they're virtually identical.

There's also about Hypothesis cache of about 6 MB for the main branch. For Hypothesis, PRs usually use the main cache and don't need to write their own cache.

However, the docs workflow only runs for PRs, so main/3.* branches never get to save a cache. If they had, the vast majority would just use a cache from main and carry on. No need to save their own PR cache.

We can do this by letting this workflow run on main and 3.*, and also limit to only run if one of these files change:

• Doc/pylock.toml
• Doc/requirements.txt
• .github/workflows/reusable-docs.yml