ci: clear old caches to avoid master branch cache trashing #14174
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kasper93
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I tried to keep things simple and not overcomplicate with some artifacts passing PR number or other "tricks" that initially made sense, but after all doing validation on all cache items should be good. EDIT: Note that this will run only after merged to master. PR has no ability to run this code for security reasons, and that a good thing. (little bit annoying to test though :)) |
Dudemanguy
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May 19, 2024
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Ok, let's see how it works in practice. |
GitHub cache action doesn't allow updating cache with the same key. We workaround this by saving the cache with a unique key each time (added timestamp). This works fine, but since there is a limit on cumulative storage size for all caches, it can force the master branch cache to be evicted if a lot of PRs are updated. Cache is evicted with LRU policy, so as long as master branch cache is used it should stay alive, but it can happen that only PR specifc caches were only used. As a reminder, PRs can access the master cache, but they are isolated from each other. Because of this, it is important to keep the master cache, which is available to all, alive longer. The solution is to remove all old caches per branch. This is done in a separate workflow that validates all cache items and removes ones that would never be used anyway. If PR is closed all caches per branch are removed. In other cases most recently used one is preserved. It is done in a separate workflow to limit cache manipulation access. GitHub workflows triggered by pull_request event are run in the context of the fork and does not have access to our token, which is good thing. Also it is quite awkward to get PR number which triggered build workflow, so just do a full cleanup pass.
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