Are cross-OS caches possible?

[louis-bompart]

Hi 👋

I'm trying to set up action/caches in a Node app project. Mainly, I'm trying to cache my build outputs and redistribute them in subsequent jobs in a single workflow.

The build occurs on a ubuntu-latest runner, and the subsequent jobs occur on ubuntu-latest and windows-latest.

I adapted the path parameter to use \ instead of / on windows-latest, and I'm using an OS-agnostic key for the cache (to be precise: verdaccio-${{ github.sha }}-${{ github.run_attempt }}.)

I noticed that when trying to restore the cache from windows-latest, it ends up in a no-hit, but not on ubuntu-latest (despite both jobs running after the job that uploaded the cache)

I also noticed that all examples that I could find use ${{runner-os}} in the key.

My question is then, is it possible to cache something from a linux-latest runner and restore it in a windows-latest?

[jongwooo]

@louis-bompart Cache version is unique for a combination of compression tool used for compression of cache (Gzip, Zstd, etc based on runner OS) and the path of directories being cached. If two caches have different versions, they are identified as unique cache entries. This also means that a cache created on windows-latest runner can't be restored on ubuntu-latest as cache Versions are different.

[UX3D-haertl]

Was this recently introduced? We use a workflow which caches Linux/Mac builds and restores them on Windows.
This is run on self-hosted runners and worked without problems.
We upgraded the mac runner to an ARM one, and now the cache misses on Windows (not on Mac if run again).
Linux still works.
Is there a possibility to fix this?

[jongwooo]

@louis-bompart Can I see the workflow by any chance? I'm curious too :)

[louis-bompart]

Hey @jongwooo , yep: https://github.com/coveo/cli/blob/master/.github/workflows/build.yml

[UX3D-haertl]

This is the code responsible for deciding which compression to use:

function getCompressionMethod() {
    return __awaiter(this, void 0, void 0, function* () {
        if (process.platform === 'win32' && !(yield isGnuTarInstalled())) {
            // Disable zstd due to bug https://github.com/actions/cache/issues/301
            return constants_1.CompressionMethod.Gzip;
        }
        const versionOutput = yield getVersion('zstd');
        const version = semver.clean(versionOutput);
        if (!versionOutput.toLowerCase().includes('zstd command line interface')) {
            // zstd is not installed
            return constants_1.CompressionMethod.Gzip;
        }
        else if (!version || semver.lt(version, 'v1.3.2')) {
            // zstd is installed but using a version earlier than v1.3.2
            // v1.3.2 is required to use the `--long` options in zstd
            return constants_1.CompressionMethod.ZstdWithoutLong;
        }
        else {
            return constants_1.CompressionMethod.Zstd;
        }
    });
}

function isGnuTarInstalled() {
    return __awaiter(this, void 0, void 0, function* () {
        const versionOutput = yield getVersion('tar');
        return versionOutput.toLowerCase().includes('gnu tar');
    });
}

Therefore, if you can manage to use the same compression everywhere, it should work.
So either install zstd everywhere, or uninstall it everywhere.
In my instance, zstd was only installed on Mac. Therefore, Linux to Windows worked but not Mac to Windows.

[UX3D-haertl]

I just tried installing GNU tar on Windows. Now the cache was hit, but the following error occurs:
C:\Program Files (x86)\GnuWin32\bin\tar.exe: Cannot fork: Function not implemented
It seems like this operation is not supported on Windows. Is there a reason why cache checks gnu tar specifically?
bsdtar would work better and is already installed on Windows by default.

[Phantsure]

We are working on cross os caching. We have also released a release in beta as well. You can test the functionality with tag actions/cache@3.1.0-beta. Original discussion: #1019