GHA export fails with "Cache already exists"

[lucacome]

The workflow is using the following in a matrix (not sure if it's relevant)

  cache-from: type=gha
  cache-to: type=gha,mode=max

and sometimes I get this

#17 ERROR: error writing layer blob: Cache already exists. Scope: refs/pull/1892/merge, Key: buildkit-blob-1-sha256:74328d539a236952c80a22e6e6e7c52d4fed86fb10a7d0b317c8fbb42d5c36fa, Version: 693bb7016429d80366022f036f84856888c9f13e00145f5f6f4dce303a38d6f2
------
 > exporting cache:
------
error: failed to solve: error writing layer blob: Cache already exists. Scope: refs/pull/1892/merge, Key: buildkit-blob-1-sha256:74328d539a236952c80a22e6e6e7c52d4fed86fb10a7d0b317c8fbb42d5c36fa, Version: 693bb7016429d80366022f036f84856888c9f13e00145f5f6f4dce303a38d6f2
Error: buildx failed with: error: failed to solve: error writing layer blob: Cache already exists. Scope: refs/pull/1892/merge, Key: buildkit-blob-1-sha256:74328d539a236952c80a22e6e6e7c52d4fed86fb10a7d0b317c8fbb42d5c36fa, Version: 693bb7016429d80366022f036f84856888c9f13e00145f5f6f4dce303a38d6f2

I tried searching for the sha in the other builds in the matrix, but couldn't find it, I'm assuming it's from a previous run?

[crazy-max]

@lucacome

in a matrix (not sure if it's relevant)

Could be relevant but can't tell without repro. Would suggest to define scope for each matrix:

  cache-from: type=gha,scope=${{ matrix.name }}-cache
  cache-to: type=gha,scope=${{ matrix.name }}-cache,mode=max

[lucacome]

@crazy-max thanks for the response. We had to disable caching for now since all the builds were failing, but could you provide more info on what the scope does? I couldn't find much in the docs.

Should I have a different scope for every image that I build? Like if one of the images in the matrix is built in a previous step too, do I need the same scope for caching to work?

[crazy-max]

@lucacome

I couldn't find much in the docs.

https://github.com/moby/buildkit#github-actions-cache-experimental

Should I have a different scope for every image that I build? Like if one of the images in the matrix is built in a previous step too, do I need the same scope for caching to work?

If you talk about this workflow, scope is pretty much the same as defining a specific folder for the local cache destination like you do atm with actions/cache. So you have to define a scope per image:

  release-docker:
    name: Release Images
    runs-on: ubuntu-20.04
    needs: [binary]
    strategy:
      matrix:
        include:
          - scope: nginx-ingress
            tags: |
              nginx/nginx-ingress:${{ needs.binary.outputs.version }}
              nginx/nginx-ingress:latest
            type: debian
            platforms: linux/arm,linux/arm64,linux/amd64,linux/ppc64le,linux/s390x
          - scope: nginx-ingress-alpine
            tags: |
              nginx/nginx-ingress:${{ needs.binary.outputs.version }}-alpine
              nginx/nginx-ingress:alpine
            type: alpine
            platforms: linux/arm,linux/arm64,linux/amd64,linux/ppc64le,linux/s390x
          - scope: nginx-ingress-ubi
            tags: |
              nginx/nginx-ingress:${{ needs.binary.outputs.version }}-ubi
              nginx/nginx-ingress:ubi
            type: ubi
            platforms: linux/arm64,linux/amd64
    steps:
      - name: Checkout Repository
        uses: actions/checkout@v2
      ...
      - name: Push to Dockerhub
        uses: docker/build-push-action@v2
        with:
          file: build/Dockerfile
          context: '.'
          cache-from: type=gha,scope=${{ matrix.scope }}
          cache-to: type=gha,scope=${{ matrix.scope }},mode=max
          target: goreleaser
          tags: ${{ matrix.tags }}
          platforms: ${{ matrix.platforms }}
          push: true
          build-args: |
            BUILD_OS=${{ matrix.type }}
            IC_VERSION=${GITHUB_REF#refs/tags/}
            NGINX_VERSION=${{ steps.commit.outputs.nginx_version }}
            DATE=${{ steps.commit.outputs.date }}
            GIT_COMMIT=${{ github.sha }}

[vterdunov]

Similar problem. It's build without matrix. Scope already used.

BuildKit version
  moby/buildkit:buildx-stable-1 => buildkitd github.com/moby/buildkit v0.9.0 c8bb937807d405d92be91f06ce2629e6202ac7a9

env:
  SERVICE_NAME: web

...

      - name: Set up Docker Buildx
        id: buildx
        uses: docker/setup-buildx-action@v1

...

      - name: Build image
        uses: docker/build-push-action@v2
        id: docker_build
        with:
          context: web
          builder: ${{ steps.buildx.outputs.name }}
          file: ./web/Dockerfile
          push: true
          tags: ${{ steps.docker_meta.outputs.tags }}
          labels: ${{ steps.docker_meta.outputs.labels }}
          cache-from: type=gha,scope=${{ env.SERVICE_NAME }}
          cache-to: type=gha,scope=${{ env.SERVICE_NAME }},mode=max

The error is:

#34 writing layer sha256:1e987daa2432270bbfaf366f57583c93b48e0ee6c9fe54fe7f4030b84095627f 0.0s done
#34 ERROR: error writing layer blob: Cache already exists. Scope: refs/heads/master, Key: buildkit-blob-1-sha256:1e987daa2432270bbfaf366f57583c93b48e0ee6c9fe54fe7f4030b84095627f, Version: 693bb7016429d80366022f036f84856888c9f13e00145f5f6f4dce303a38d6f2
------
 > exporting cache:
------
error: failed to solve: error writing layer blob: Cache already exists. Scope: refs/heads/master, Key: buildkit-blob-1-sha256:1e987daa2432270bbfaf366f57583c93b48e0ee6c9fe54fe7f4030b84095627f, Version: 693bb7016429d80366022f036f84856888c9f13e00145f5f6f4dce303a38d6f2
Error: buildx failed with: error: failed to solve: error writing layer blob: Cache already exists. Scope: refs/heads/master, Key: buildkit-blob-1-sha256:1e987daa2432270bbfaf366f57583c93b48e0ee6c9fe54fe7f4030b84095627f, Version: 693bb7016429d80366022f036f84856888c9f13e00145f5f6f4dce303a38d6f2

I noticed Scope: refs/heads/master, i believed it should be web
At the same time other services builds without problems.

[lucacome]

I tried adding the scope but I still get

error: failed to solve: error writing layer blob: Cache already exists. Scope: refs/pull/1913/merge, Key: buildkit-blob-1-sha256:e1acddbe380c63f0de4b77d3f287b7c81cd9d89563a230692378126b46ea6546, Version: 693bb7016429d80366022f036f84856888c9f13e00145f5f6f4dce303a38d6f2

Seems like the scope is not used?

[jnordberg]

Have the same issue, scope is set but does not seem to be used:

      - name: Build and push
        uses: docker/build-push-action@v2
        with:
          context: .
          push: ${{ github.event_name != 'pull_request' }}
          build-args: ${{ matrix.config.args }}
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha,scope=${{ matrix.config.name }}
          cache-to: type=gha,mode=max,scope=${{ matrix.config.name }}

Error: buildx failed with: error: failed to solve: error writing layer blob: Cache already exists. Scope: refs/tags/v1.0.0-test-ff3, Key: buildkit-blob-1-sha256:705bb4cb554eb7751fd21a994f6f32aee582fbe5ea43037db6c43d321763992b, Version: 693bb7016429d80366022f036f84856888c9f13e00145f5f6f4dce303a38d6f2