'Job A' unable to access cache of downstream 'Job B'

Heya! I have these two jobs where Job B needs Job A: https://github.com/returntocorp/semgrep/blob/a9e8b90c2e3de705c54ca311b414608ffaa32ff7/.github/workflows/tests.yml#L15-L67

Both jobs do this:

        uses: actions/cache@v3
        with:
          path: ocaml-build-artifacts.tgz
          key: foo

But only Job B ever builds that artifact, while Job A only tries to restore it to see if Job B can be skipped altogether.

Now, I don’t see why this wouldn’t work, but it does not, see these logs:

• Job A fails to restore the cache: https://github.com/returntocorp/semgrep/runs/6823861478?check_suite_focus=true#step:5:38
• Job B successfully restores the cache: https://github.com/returntocorp/semgrep/runs/6823863765?check_suite_focus=true#step:6:61

I would expect the restore to succeed in Job A as well.

[bishal-pdMSFT]

@underyx this is happening because of two different OS containers. Due to that, in Job A case zstd is used for compression. Can be inferred from logs

##[debug]Checking zstd --version
##[debug]*** zstd command line interface 64-bits v1.5.2, by Yann Collet ***

In Job B, zstd is not found and hence it falls back to gzip

##[debug]Checking zstd --version
##[debug]Unable to locate executable file: zstd. Please verify either the file path exists or the file can be found within a directory specified by the PATH environment variable. Also check the file mode to verify the file is executable.

Whenever compression technique is different, the caches are treated as unique even though cache-key is same. Otherwise the de-compression will fail.

The fix is either to use same OS or ensure that same tools (e.g. zstd) is installed on both.

[Phantsure]

Have updated the error message to show other versions on cache miss if debug is on: https://github.com/actions/toolkit/blob/main/packages/cache/src/internal/cacheHttpClient.ts#L132 Closing this issue