setup-buildkit/action.yml

name: 'Setup BuildKit (with labels)'
description: 'Idempotently start a labeled buildkitd container and point buildx at it via the remote driver. The default docker-container driver cannot set container labels, and the Docker API has no PATCH-labels for existing containers — so we manage the container ourselves and Watchtower/Dockhand see the labels.'
inputs:
  container_name:
    description: 'Name of the buildkitd container'
    required: false
    default: 'buildkitd'
  image:
    description: 'BuildKit image'
    required: false
    default: 'moby/buildkit:buildx-stable-1'
  monitor_only:
    description: 'Value for com.centurylinklabs.watchtower.monitor-only'
    required: false
    default: 'false'
  dockhand_notify:
    description: 'Value for dockhand.notify'
    required: false
    default: 'false'
  cleanup:
    description: 'Stop the buildkitd container after the job (idle cleanup; container restarts on demand on the next run)'
    required: false
    default: 'true'

runs:
  using: 'composite'
  steps:
    - name: Start BuildKit container (with labels)
      shell: bash
      run: |
        docker ps -a --format '{{.Names}}' | grep -qx '${{ inputs.container_name }}' || \
        docker run -d --name ${{ inputs.container_name }} --privileged \
          --restart unless-stopped \
          --label com.centurylinklabs.watchtower.monitor-only=${{ inputs.monitor_only }} \
          --label dockhand.notify=${{ inputs.dockhand_notify }} \
          ${{ inputs.image }}

    - name: Set up Docker Buildx
      uses: docker/setup-buildx-action@v4
      with:
        driver: remote
        endpoint: docker-container://${{ inputs.container_name }}

    - name: Stop BuildKit (idle cleanup)
      if: ${{ inputs.cleanup == 'true' && always() }}
      shell: bash
      run: docker stop ${{ inputs.container_name }} || true