action.yml

name: "Ephemeral GCE GitHub self-hosted runner"
description: >-
  Creates ephemeral GCE based GitHub Action self-hosted runner.
  It uses startup script to bootstrap the VM.
branding:
  icon: triangle
  color: purple
inputs:
  runner_token:
    description: >-
      GitHub auth token, needs `repo`/`public_repo` scope: https://docs.github.com/en/rest/reference/actions#self-hosted-runners.
    required: true
  project_id:
    description: >-
      ID of the Google Cloud Platform project. If provided, this will configure gcloud to use this project ID.
    required: false
    default: public-github-runners
  machine_zone:
    description: GCE zone
    default: "europe-west1-b"
    required: false
  machine_type:
    description: GCE machine type; https://cloud.google.com/compute/docs/machine-types
    default: "n2d-standard-32"
    required: true
  disk_size:
    description: VM disk size.
    required: false
    default: 500GB
  image_project:
    description: >
      The Google Cloud project against which all image and image family references will be resolved.
    required: false
    default: public-github-runners
  image:
    description: Specifies the name of the image that the disk will be initialized with. If not provided, will use the latest gh-runner-* image.
    required: false
  image_family:
    description: The image family for the operating system that the boot disk will be initialized with.
    required: false
  label:
    description: >-
      Runner label. Can be set to override the VM name to recreate a runner with a specific label,
      e.g. to replace a runner that was shutdown. If set, 'task' will be ignored.
    required: false
  scopes:
    description: Scopes granted to the VM, defaults to full access (cloud-platform).
    default: cloud-platform
    required: true
  shutdown_timeout:
    description: "Shutdown grace period (in seconds)."
    default: 30s
    required: true
  task:
    description: Additional context about the workflow
    default: default
    required: true
  gcp_credentials:
    description: GCP JSON credentials
    required: true

outputs:
  label:
    description: >-
      Unique runner label. This label can be used to request a specific
      runner for the workflow job.
    value: ${{ steps.gce-github-runner-script.outputs.label }}
  machine-zone:
    description: >-
      VM availability zone
    value: ${{ steps.gce-github-runner-script.outputs.machine-zone }}
runs:
  using: "composite"
  steps:
    - name: Check if we are allowed to run
      id: check-repository
      if: github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
      shell: bash
      run: |
        echo "❌ Job actions are not allowed to run in forks" >> $GITHUB_STEP_SUMMARY
        exit 1
    - name: Checkout repository
      uses: actions/checkout@v4
    - name: Authenticate to Google Cloud
      id: auth
      if: github.event.pull_request.head.repo.full_name == github.event.pull_request.base.repo.full_name
      uses: google-github-actions/auth@v1
      with:
        credentials_json: ${{ inputs.gcp_credentials }}
    - name: Activate GCP service account
      id: gcloud-auth
      if: github.event.pull_request.head.repo.full_name == github.event.pull_request.base.repo.full_name
      shell: bash
      run: |
        gcloud auth activate-service-account --key-file ${{ steps.auth.outputs.credentials_file_path }}
    - name: Get latest runner image
      id: get-image
      if: github.event.pull_request.head.repo.full_name == github.event.pull_request.base.repo.full_name && inputs.image == ''
      shell: bash
      run: |
        LATEST_IMAGE=$(gcloud compute images list \
          --project=${{ inputs.image_project }} \
          --filter="name~'gh-runner-.*'" \
          --sort-by="~creationTimestamp" \
          --format="value(name)" \
          --limit=1)
        echo "image=${LATEST_IMAGE}" >> $GITHUB_OUTPUT
        echo "Using latest image: ${LATEST_IMAGE}"
    - name: Create GCE VM
      id: gce-github-runner-script
      if: github.event.pull_request.head.repo.full_name == github.event.pull_request.base.repo.full_name
      shell: bash
      run: |
        set -x
        
        IMAGE_TO_USE="${{ inputs.image }}"
        if [ -z "${IMAGE_TO_USE}" ]; then
          IMAGE_TO_USE="${{ steps.get-image.outputs.image }}"
        fi

        ${{ github.action_path }}/action.sh \
          --command=start \
          --runner_token=${{ inputs.runner_token }} \
          --project_id=${{ inputs.project_id }} \
          --machine_zone=${{ inputs.machine_zone }} \
          --machine_type=${{ inputs.machine_type }} \
          --disk_size=${{ inputs.disk_size }} \
          --scopes=${{ inputs.scopes }} \
          --shutdown_timeout=${{ inputs.shutdown_timeout }} \
          --image_project=${{ inputs.image_project }} \
          --image="${IMAGE_TO_USE}" \
          --image_family=${{ inputs.image_family }} \
          --label=${{ inputs.label }} \
          --boot_disk_type=pd-ssd \
          --task=${{ inputs.task }}