What are Service Containers

Service containers in GitHub Actions let you spin up Docker containers alongside your workflow jobs, providing on-demand services—such as databases, caches, or message queues—for your CI/CD pipelines. By defining services in your workflow YAML, you can run integration and end-to-end tests without managing external infrastructure.

Basic Workflow Without Service Containers

The simplest workflow runs tests immediately after code checkout and dependency installation. It’s ideal for unit tests that don’t require external services.

name: My Awesome App
on: push

jobs:
  unit-testing:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout Code
        uses: actions/checkout@v3

      - name: Set Up Node.js
        uses: actions/setup-node@v3
        with:
          node-version: '20'

      - name: Install Dependencies
        run: npm install

      - name: Run Tests
        run: npm test

Adding a MongoDB Service Container

To test against a MongoDB database, add a services section. This example maps the container’s default MongoDB port to a host port on the runner:

name: My Awesome App
on: push

jobs:
  unit-testing:
    runs-on: ubuntu-latest

    services:
      mongodb-service:
        image: mongo:latest
        ports:
          - 12345:27017

    steps:
      - name: Checkout Code
        uses: actions/checkout@v3

      - name: Set Up Node.js
        uses: actions/setup-node@v3
        with:
          node-version: '20'

      - name: Install Dependencies
        run: npm install

      - name: Run Tests
        run: |
          export MONGODB_HOST=localhost
          export MONGODB_PORT=12345
          npm test

Here’s what happens:

1. Service Container: mongo:latest runs as mongodb-service.
2. Port Mapping: Container port 27017 is mapped to runner port 12345.
3. Environment Variables: Tests connect to localhost:12345.

Common Service Containers for CI Workflows

Running Steps Inside a Job Container with Services

You can isolate your build environment by specifying a job container and still link to service containers through the Docker network:

name: My Awesome App
on: push

jobs:
  unit-testing:
    runs-on: ubuntu-latest

    container:
      image: ghcr.io/node-and-packages:20

    services:
      mongodb-service:
        image: mongo:latest

    env:
      MONGODB_HOST: mongodb-service
      MONGODB_PORT: 27017

    steps:
      - name: Checkout Code
        uses: actions/checkout@v3

      - name: Install Dependencies
        run: npm install

      - name: Run Tests
        run: npm test

Key points:

• Job Container runs every step inside ghcr.io/node-and-packages:20.
• Service Container mongodb-service is discoverable on the default Docker bridge network.
• Networking uses the service container’s hostname (mongodb-service) without port mapping.

Links and References

• GitHub Actions: Services
• GitHub Actions: Workflow Syntax
• Docker Hub
• Kubernetes Basics