CI/CD Pipeline Tutorial from Scratch

Push Code → Lint → Test → Build → Deploy Staging → Deploy Production
                                        ↑                    ↑
                                   Automatic            Manual gate
                                   (on PR merge)        (on release tag)

name: CI

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 22
          cache: npm
      - run: npm ci
      - run: npm run lint

  test:
    runs-on: ubuntu-latest
    needs: lint
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 22
          cache: npm
      - run: npm ci
      - run: npm test -- --coverage
      - uses: actions/upload-artifact@v4
        with:
          name: coverage
          path: coverage/

  build:
    runs-on: ubuntu-latest
    needs: test
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 22
          cache: npm
      - run: npm ci
      - run: npm run build
      - uses: actions/upload-artifact@v4
        with:
          name: build
          path: dist/

  docker:
    runs-on: ubuntu-latest
    needs: build
    if: github.ref == 'refs/heads/main'
    permissions:
      contents: read
      packages: write
    steps:
      - uses: actions/checkout@v4

      - uses: docker/login-action@v3
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - uses: docker/build-push-action@v6
        with:
          push: true
          tags: |
            ghcr.io/${{ github.repository }}:latest
            ghcr.io/${{ github.repository }}:${{ github.sha }}
          cache-from: type=gha
          cache-to: type=gha,mode=max

  deploy-staging:
    runs-on: ubuntu-latest
    needs: docker
    environment: staging
    steps:
      - uses: actions/checkout@v4

      - name: Deploy to staging
        run: |
          kubectl set image deployment/app \
            app=ghcr.io/${{ github.repository }}:${{ github.sha }}
        env:
          KUBECONFIG_DATA: ${{ secrets.STAGING_KUBECONFIG }}

      - name: Wait for rollout
        run: kubectl rollout status deployment/app --timeout=120s

      - name: Smoke test
        run: |
          STAGING_URL="${{ vars.STAGING_URL }}"
          STATUS=$(curl -s -o /dev/null -w "%{http_code}" "$STAGING_URL/health")
          if [ "$STATUS" != "200" ]; then
            echo "Smoke test failed: HTTP $STATUS"
            exit 1
          fi

  deploy-production:
    runs-on: ubuntu-latest
    needs: deploy-staging
    environment:
      name: production
      url: https://app.example.com
    steps:
      - uses: actions/checkout@v4

      - name: Deploy to production
        run: |
          kubectl set image deployment/app \
            app=ghcr.io/${{ github.repository }}:${{ github.sha }}
        env:
          KUBECONFIG_DATA: ${{ secrets.PROD_KUBECONFIG }}

      - name: Wait for rollout
        run: kubectl rollout status deployment/app --timeout=180s

      - name: Health check
        run: |
          for i in {1..5}; do
            STATUS=$(curl -s -o /dev/null -w "%{http_code}" "https://app.example.com/health")
            if [ "$STATUS" = "200" ]; then exit 0; fi
            sleep 10
          done
          echo "Health check failed"
          exit 1

      - name: Notify on success
        if: success()
        uses: slackapi/slack-github-action@v2
        with:
          webhook: ${{ secrets.SLACK_WEBHOOK }}
          payload: |
            {"text": "✅ Deployed ${{ github.sha }} to production"}

      - name: Notify on failure
        if: failure()
        uses: slackapi/slack-github-action@v2
        with:
          webhook: ${{ secrets.SLACK_WEBHOOK }}
          payload: |
            {"text": "❌ Deploy failed for ${{ github.sha }}"}

PR opened
  └─ lint → test → build (feedback on PR)

PR merged to main
  └─ lint → test → build → docker → staging → production
                                        │          │
                                    automatic   approval gate

  test:
    strategy:
      matrix:
        node-version: [20, 22]
        os: [ubuntu-latest, macos-latest]
    runs-on: ${{ matrix.os }}
    steps:
      - uses: actions/setup-node@v4
        with:
          node-version: ${{ matrix.node-version }}
      - run: npm test