Possible to cache under two keys?

[Mahoney]

Hi all,

I'd quite like to cache by SHA and by branch name, so that if I tag a commit that has already been built on a branch then it uses the cache for that commit to rebuild it, but if I build a branch then I benefit from a cache populated from the previous build on that branch.

Is that possible?

If I use this cache key ${{ github.ref }}-${{ github.sha }} then the branch run will cache as main-abcdef and the tag run will look up with 0.1.0-abcdef and it will miss.

If I use this cache key ${{ github.sha }}-${{ github.ref }} then the branch build will cache as abcdef-main, the tag build will look up with abcdef-0.1.0 and it will hit the abcdef SHA cache, but a subsequent commit to main will look up with123456-main and miss.

I suppose I'd really like to cache it under two keys - once under ${{ github.ref }} and once under ${{github.sha}}. Then I can use this:

restore-keys: |
  ${{ github.sha }}
  ${{ github.ref }}

and (I think!) it'll use the SHA cache for preference and fall back to the branch name cache if there's no SHA cache. But I don't think caching under two keys is supported? Am I wrong?

Anyone got a nice solution to this?

[Mahoney]

Ignore the below - looks like my testing missed that it was actually the second restore ket I was hitting not the first.

Answering my own question - testing suggests you can use globs in the restore-keys path. So the following does what I need:

    steps:
      - uses: actions/cache@v2
        with:
          path: cached.txt
          key: ${{ github.ref }}-${{ github.sha }}
          restore-keys: |
            **-${{ github.sha }}
            ${{ github.ref }}-

because **-${{ github.sha }} will always match ${{ github.ref }}-${{ github.sha }} regardless of the value of ${{ github.ref }}.

You can have a look at https://github.com/Mahoney-playground/action-tests/actions to see it working.

[Mahoney]

Raised #740 but there doesn't seems to be much feedback from actual GitHub people on issues in there.