Allow updating an existing cache

[davidsbond]

GitHub actions supports caching across builds which is super powerful. However, once a cache has been saved it can no longer be modified. While this is fine for most scenarios where you need the cache there are a few times when you would like to update it.

I created this PR on the actual cache action to allow updating a cache when providing it in configuration:

actions/cache#353

I created it after reading the related issue:

actions/cache#342

However, it seems like something either needs to change in this package or server-side on the actions cache.

My use-case for wanting to update a cache is when using GitHub actions in golang projects. Go supports a test cache which allows tests to be skipped if the code they use has not changed, which can significantly improve test times (especially in large projects). Each time I run my tests, I'd like to maintain a single cache for tests, that way, when a run completes I can update the cache and all my workflows share a single test cache

There are some extra use-cases described on the issue above.

[smorimoto]

I would also like to support this proposal.

[half2me]

I need this too

[eLarocque]

same

[CAMOBAP]

[Blissful89]

#poke

[hyperxpro]

+1

[stephanrotolante]

+1

[DenizUgur]

+1

[emrebayramc]

+1

[YegorMedvedev]

In the meantime, here's a workaround that I use:

- name: Get cache
  uses: actions/cache@v3
  with:
    path: ... # a list of cache paths
    key: ${{ runner.os }}-my-cache-${{ github.head_ref }}-${{ hashFiles(...for example yarn.lock...) }}

- name: Do something to change a cache
  run: ...

- name: Enforce cache update for a local NX cache
  run: |
    STATE_CACHE_KEY="${{ runner.os }}-my-cache-${{ github.head_ref }}-${{ hashFiles(...) }}"
    echo "STATE_CACHE_KEY=${STATE_CACHE_KEY}" >> $GITHUB_ENV

[emrebayramc]

+1

[wind57]

+1

[arpanrec]

+1

[bexsoft]

+1

[nnsay]

+1

[dsame]

Updating the cache is supposed to be done with restore-keys

This input allows to restore the cache even if it is not fully matched. And to generate the new key to update the cache do one of:

1. include the changing file into ${{ hashFiles(...) }}
2. set output of the previous step and include it into the key

[isaacbowen]

@dsame This is exactly what I was missing. Thank you for sharing! Super super super helpful. ❤️

[pauldraper]

@dsame's workaround is the best available currently, though it does have problems.

Github hard-limits repos to 10GB of caches. So creating lots of caches can push other less-frequent-but-helpful caches to deletion. Whereas if you could update/replace an existing cache, that wouldn't happen.

[lcswillems]

On Gitlab or a lot of other different CI/CD tools, this is built-in 😭 Such a pain not to have this!

[trallnag]

I came across this documentation that uses artifacts across workflow runs as a workaround for this: https://github.com/renovatebot/github-action?tab=readme-ov-file#persisting-the-repository-cache

[BillyTom]

I have tried several workarounds to get actions/cache to update my existing test results correctly. But my conclusion is that it is much easier to use actions/upload-artifact and actions/download-artifact instead.

I have a matrix job that creates test results for a dozen different features. Each job in the matrix uploads its test results with:

  - name: "Upload test results"
    uses: actions/upload-artifact@v4
    with:
      name: test-result-${{ matrix.feature.name }}
      path: |
        frontend/cypress/screenshots
        frontend/cypress/reports

After the matrix job there comes another job that aggregates all test results into one single folder:

  - uses: actions/download-artifact@v4
    with:
      pattern: test-result-*
      merge-multiple: true
      path: frontend/cypress

After that you could just use actions/cache to create a new cache for the folder with the combined test results.

Optional: Since the individual artifacts are now obsolete you can perform a cleanup operation with:

  - name: "Delete obsolete artifacts"
    uses: geekyeggo/delete-artifact@65041433121f7239077fa20be14c0690f70569de
    with:
      name: test-result-*
      useGlob: true

[Lolicchi]

+8

[hamistao]

+9. Need this to cache a vulnerability database to improve the performance and reliability of our CI workflow.

[mabar]

Using less specific key for loading cache than for saving (e.g. example-1 for saving and example- for loading) is the correct solution. Simply adding run ID to the key is enough to keep the cache always up to date.

Cache can currently be restored from the default branch - that allows use of cache for newly created PRs and branches from the start. Updating an existing cache would require removal of that feature because e.g. updating cache in third party PR and using it on master would eventually result in bad consequences.

Problem is that it is not explained in the documentation.

Secondary, cache size is limited and there is no way how to remove less useful and outdated cache that is likely to be never used again, causing more useful cache to be deleted.
I would e.g. like to have an ability to delete branch-specific cache when it is deleted and delete cache, that matches restore-keys but has a newer version.

Also having a button for deleting all the cache would be quite helpful for debugging cache-related issues.