Cache Incompatibility Between ARC and Non-ARC Runners in GitHub Actions

[GeunSam2]

Description

There is a cache compatibility issue between ARC (Action Runner Controller) runners and non-ARC runners in GitHub Actions. Caches created by ARC runners cannot be restored by non-ARC runners, and vice versa. This issue limits the interoperability between different runner environments, causing inefficiencies in workflows that utilize both ARC and non-ARC runners.

Steps to Reproduce

1. Scenario 1: Non-ARC to ARC

   • First Job: Non-ARC Runner (e.g., Self-hosted, github hosted ...)

     jobs:
       build:
         runs-on: self-hosted
         steps:
           - uses: actions/checkout@v4
     
           - name: Generate Cache
             id: generate-cache
             run: |
               mkdir -p ./path/to/cache
               echo "This is a test cache" > ./path/to/cache/test.txt
     
             - name: Save Cache
               uses: actions/cache/save@v4
               with:
                 path: ./path/to/cache
                 key: cache-${{ github.run_id }}
                 enableCrossOsArchive: true
     

   • Second Job: ARC Runner

     jobs:
       test:
         needs: build
         runs-on: k8s-ubuntu-x64-4cores
         steps:
           - uses: actions/checkout@v4
     
           - name: Restore Cache
             id: restore-cache
             uses: actions/cache/restore@v4
             with:
               path: ./path/to/cache
               key: cache-${{ needs.build.outputs.cache-key }}
               restore-keys: cache-
               enableCrossOsArchive: true
     
           - name: Check Cache
             run: |
               if [ -f "./path/to/cache/test.txt" ]; then
                 echo "Cache restored successfully"
               else
                 echo "Cache not found"
               fi
     

2. Scenario 2: ARC to Non-ARC

   • First Job: ARC Runner

     jobs:
       build:
         runs-on: k8s-ubuntu-x64-4cores
         steps:
           - uses: actions/checkout@v4
     
           - name: Generate Cache
             id: generate-cache
             run: |
               mkdir -p ./path/to/cache
               echo "This is a test cache" > ./path/to/cache/test.txt
     
             - name: Save Cache
               uses: actions/cache/save@v4
               with:
                 path: ./path/to/cache
                 key: cache-${{ github.run_id }}
                 enableCrossOsArchive: true
     

   • Second Job: Non-ARC Runner

     jobs:
       test:
         needs: build
         runs-on: self-hosted
         steps:
           - uses: actions/checkout@v4
     
           - name: Restore Cache
             id: restore-cache
             uses: actions/cache/restore@v4
             with:
               path: ./path/to/cache
               key: cache-${{ needs.build.outputs.cache-key }}
               restore-keys: cache-
               enableCrossOsArchive: true
     
           - name: Check Cache
             run: |
               if [ -f "./path/to/cache/test.txt" ]; then
                 echo "Cache restored successfully"
               else
                 echo "Cache not found"
               fi
     

Expected Behavior

The cache should be successfully restored across different runner environments.

Actual Behavior

The cache fails to restore, displaying a "Cache not found" message, despite the cache being available and correctly generated.

Additional Information

• The cache is verified to exist and is accessible within the repository's cache storage.
• The issue occurs in both directions: ARC to non-ARC and non-ARC to ARC.
• Both environments have enableCrossOsArchive set to true to allow cross-OS cache compatibility.

Environment Details

• Non-ARC Runner: Self-hosted, running on a different operating system.
• ARC Runner: Kubernetes-based runner managed by ARC in a Kubernetes cluster.
• GitHub Actions Cache Version: v4

Impact

This issue limits the flexibility and interoperability of using different runner types within the same workflow, leading to inefficiencies and potential workflow redesign to avoid mixed runner environments.

[sb185296]

i have same problem ! what we can do to fix it ???

[vlad-oj]

I suppose it has the same nature as described here https://github.com/actions/cache/issues/1455#issuecomment-2328358604

[deitch]

The problem, I believe, is here:

  const workspace = process.env['GITHUB_WORKSPACE'] ?? process.cwd()
  const globber = await glob.create(patterns.join('\n'), {
    implicitDescendants: false
  })

  for await (const file of globber.globGenerator()) {
    const relativeFile = path
      .relative(workspace, file)
      .replace(new RegExp(`\\${path.sep}`, 'g'), '/')
    core.debug(`Matched: ${relativeFile}`)

It uses path.relative() to resolve file relative to workspace, but that is not what path.relative does. The docs state:

The path.relative() method returns the relative path from from to to based on the current working directory. If from and to each resolve to the same path (after calling path.resolve() on each), a zero-length string is returned.

It is doing the relative path to something based on the current working directory. Here is a simple test.

$ mkdir /tmp/foo && cd /tmp/foo
$ node
> path.relative("/a/b/c", "../q")
'../../../tmp/q'

I think they were looking for ../q, i.e. "q as relative to /a/b/c, and not "how do I get to q relative to abc given my current working directory?"

I should open an issue there, or make a dedicated one here.