action.yml

---
name: Start EC2 actions runner
description: Starts and registers a self-hosted GitHub actions repository runner (Linux on EC2)

inputs:
  aws-region:
    description: AWS region, e.g. eu-west-1
    required: true
  aws-access-key-id:
    description: AWS access key ID (pass via GitHub secret). Required only if **not** using OIDC
    required: false
  aws-secret-access-key:
    description: AWS secret access key (pass via GitHub secret). Required only if **not** using OIDC
    required: false
  aws-role-to-assume:
    description: AWS IAM role (ARN) to assume, for launching the instance. Required if using OIDC (AssumeRoleWithWebIdentity)
    required: false
  aws-launch-template:
    description: AWS EC2 launch template (AWS CLI format, e.g. LaunchTemplateId=lt-0abcd290751193123)
    required: true
  github-token:
    description: GitHub token (PAT with repo scope, pass via GitHub secret)
    required: true
  github-repo:
    description: Github repository, e.g. ghost/example. Defaults to current repository
    default: ${{ github.repository }}
    required: false
  runner-labels:
    description: Extra runner labels (comma-separated). Can be referenced in job 'runs-on'
    required: false
  runner-home:
    description: Directory that contains actions-runner software and scripts
    required: false
    default: /home/ubuntu/actions-runner
  runner-user:
    description: User to run the actions-runner service as
    required: false
    default: ubuntu
  auto-shutdown-at:
    description: Automatically shutdown instance at the specified time?. E.g. 'now + 72 hours'. Requires https://linux.die.net/man/1/at
    required: false
  ephemeral:
    description: Flag the runner as ephemeral? An ephemeral runner is automatically de-registered after running _one_ workflow job
    required: false
    default: true

outputs:
  runner-id:
    description: GitHub repository runner id
    value: ${{ steps.main.outputs.runner-id }}
  instance-id:
    description: AWS EC2 instance id
    value: ${{ steps.main.outputs.instance-id }}

runs:
  using: composite
  steps:

    - id: auth
      uses: aws-actions/configure-aws-credentials@v1
      with:
        aws-region: ${{ inputs.aws-region }}
        aws-access-key-id: ${{ inputs.aws-access-key-id }}
        aws-secret-access-key: ${{ inputs.aws-secret-access-key }}
        role-to-assume: ${{ inputs.aws-role-to-assume }}
        role-session-name: ec2-actions-runner-start
        role-duration-seconds: 900

    - id: main
      shell: bash
      run: |
        runner_token="$(gh api -X POST "repos/$GH_REPO/actions/runners/registration-token" | jq -r .token)"
        
        if [ "$EPHEMERAL" = "true" ]; then
            extra_flags="--ephemeral"
        fi
        
        if [ -n "$RUNNER_LABELS" ]; then
            extra_labels=",$RUNNER_LABELS"
        fi
        
        user_data=$(cat <<HERE
        #!/bin/bash
        cd "$RUNNER_HOME"
        instance_id="\$(cat /var/lib/cloud/data/instance-id)"
        sudo -u "$RUNNER_USER" ./config.sh --unattended $extra_flags --name "\$instance_id" --url "https://github.com/$GH_REPO" --token "$runner_token" --labels "\$instance_id$extra_labels"
        ./svc.sh install "$RUNNER_USER"
        ./svc.sh start
        test -z "$SHUTDOWN_AT" || echo 'shutdown -P now' | at -M "$SHUTDOWN_AT"
        HERE
        )

        echo "Starting EC2 instance ..."

        instance_id="$(aws ec2 run-instances --launch-template "$LAUNCH_TEMPLATE" --user-data "$user_data" | jq -r .Instances[0].InstanceId)"

        echo "::set-output name=instance-id::$instance_id"

        echo "Started EC2 instance: $instance_id"

        echo "Waiting for repository runner to be registered ..."

        for i in {1..12}; do
            sleep 10
            runner_id=$(gh api -X GET "repos/$GH_REPO/actions/runners" -f per_page=100 \
              | jq -r --arg INSTANCE_ID "$instance_id" '.runners[] | select(.name == $INSTANCE_ID and .status == "online") | .id')
            if [ -n "$runner_id" ]; then
                break
            fi
        done

        if [ -z "$runner_id" ]; then
            echo "Runner registration failed (timed out). Terminating instance ..."
            aws ec2 terminate-instances --instance-ids "$instance_id"
            exit 1
        else
            echo "::set-output name=runner-id::$runner_id"
            echo "Repository runner started (ID: $runner_id)"
        fi
      env:
        GH_TOKEN: ${{ inputs.github-token }}
        AWS_DEFAULT_REGION: ${{ inputs.aws-region }}
        LAUNCH_TEMPLATE: ${{ inputs.aws-launch-template }}
        GH_REPO: ${{ inputs.github-repo }}
        RUNNER_HOME: ${{ inputs.runner-home }}
        RUNNER_USER: ${{ inputs.runner-user }}
        RUNNER_LABELS: ${{ inputs.runner-labels }}
        SHUTDOWN_AT: ${{ inputs.auto-shutdown-at }}
        EPHEMERAL: ${{ inputs.ephemeral }}