Zero Downtime Deployments: Blue-Green Strategy with PM2 and GitHub Actions

Zero Downtime Deployments: Blue-Green Strategy with PM2 and GitHub Actions

Blue-Green Deployment is a modern deployment strategy that minimizes downtime and risk by maintaining two production environments—Blue and Green. In this guide, we’ll combine this approach with a real-world CI/CD pipeline using GitHub Actions, PM2, and NGINX.

What is Blue-Green Deployment?

In this strategy, you maintain two environments:

• Blue - The current live environment
• Green - The new environment, where you deploy and test the latest version

Once the Green environment is confirmed stable, traffic is routed from Blue to Green via a reverse proxy like NGINX. If anything goes wrong, switching back is instant and safe.

Why Use Blue-Green Deployment?

Problem	Blue-Green Solution
Downtime during deployment	Deploy to Green in isolation, then switch traffic
Rollback complexity	Switch traffic back to Blue instantly
Live deployment anxiety	Confidence via full testing before going live

Tools We’ll Use

• PM2 – Process manager for Node.js apps
• GitHub Actions – CI/CD automation platform
• NGINX – Reverse proxy to control traffic switching
• Node.js – Application runtime

Folder Structure

Your VPS will have two directories for the app:

/var/www/myapp-blue   # Live version (on port 3000)
/var/www/myapp-green  # New version (on port 3001)

CI/CD Pipeline with GitHub Actions

We’ll use GitHub Actions to deploy to the Green environment on every push to main. After deployment, it will automatically switch NGINX to point to Green.

📄 .github/workflows/deploy.yml

name: Deploy to VPS (Blue-Green)

on:
  push:
    branches:
      - main

jobs:
  deploy:
    runs-on: ubuntu-latest

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

      - name: Setup SSH
        run: |
          mkdir -p ~/.ssh
          echo "${{ secrets.VPS_SSH_KEY }}" > ~/.ssh/id_rsa
          chmod 600 ~/.ssh/id_rsa
          ssh-keyscan -H ${{ secrets.VPS_HOST }} >> ~/.ssh/known_hosts

      - name: Deploy to Green Environment
        run: |
          ssh -o StrictHostKeyChecking=no ${{ secrets.VPS_USER }}@${{ secrets.VPS_HOST }} << 'EOF'
            echo "🔁 Connected to VPS"

            # Load Node.js environment (if using nvm)
            export NVM_DIR="\$HOME/.nvm"
            [ -s "\$NVM_DIR/nvm.sh" ] && \. "\$NVM_DIR/nvm.sh"

            # Navigate to green deployment
            cd /var/www/myapp-green
            git pull origin main
            npm install
            npx tsc

            # Restart Green instance with PM2
            pm2 start dist/index.js --name myapp-green || pm2 restart myapp-green
            pm2 save

            echo "🟢 Green deployed. Switching traffic..."

            # Update NGINX config to route to port 3001
            sudo sed -i 's/3000/3001/' /etc/nginx/sites-available/myapp
            sudo nginx -s reload

            echo "✅ Deployment complete!"
          EOF

🔐 Required GitHub Secrets

• VPS_HOST – Your server’s IP or domain
• VPS_USER – SSH username (e.g., ubuntu)
• VPS_SSH_KEY – Private key (paste as plain text)

Rollback in One Command

If something fails in Green, you can switch NGINX back to Blue:

sudo sed -i 's/3001/3000/' /etc/nginx/sites-available/myapp
sudo nginx -s reload
pm2 restart myapp-blue

Benefits Recap

• ✅ Zero-downtime deployments
• ✅ Easy rollback with one-line NGINX switch
• ✅ Automated pipeline using GitHub Actions
• ✅ Works well even for solo devs and small teams

Conclusion

Blue-Green Deployment is no longer limited to large enterprise setups. With the help of PM2, NGINX, and GitHub Actions, you can deploy robustly, confidently, and without downtime—on your own VPS. This approach provides both flexibility and safety, giving you full control over the release process.

Additional Resources

• PM2 Documentation
• SSH Action for GitHub
• NGINX Reverse Proxy