Example of blue-green deployment script using GitHub action pipeline

blue-green-deployment.yaml

name: Deploy to VPS

on:
  push:
    branches:
      - main

jobs:
  deploy:
    runs-on: ubuntu-latest
    env:
      PROJECT_REPO: [email protected]:<your-github-username>/<repo-name>.git # your git repository URL
      BLUE_NAME: "blue"
      GREEN_NAME: "green"
      BLUE_PORT: 3000 # your blue environment port. ensure it's not used by any existing process
      GREEN_PORT: 3001 # your green environment port. ensure it's not used by any existing process
      NGINX_CONF: /etc/nginx/sites-available/<your-site> # your site's nginx configuration file
      BLUE_DIR: /var/www/html/blue # your blue environment directory (customizable)
      GREEN_DIR: /var/www/html/green # your green environment directory (customizable)
    steps:
    - name: Check out the code
      uses: actions/checkout@v3

    - name: Deployment
      uses: appleboy/[email protected]
      env: 
        ACTIVE_ENV: ""
        TARGET_ENV: ""
        TARGET_DIR: ""
        TARGET_PORT: ""
      with:
        host: ${{ secrets.VPS_HOST }}
        username: ${{ secrets.VPS_USERNAME }}
        password: ${{ secrets.VPS_PASSWORD }}
        port: 22
        envs: ACTIVE_ENV,TARGET_ENV,TARGET_DIR,TARGET_PORT # list of environments used in this step 
        script: |
          echo "Deployment using blue-green is started..."
          echo "Determining the current active environment..."
          if grep -q "proxy_pass http://localhost:${{ env.BLUE_PORT }};" "${{ env.NGINX_CONF }}"; then
            export ACTIVE_ENV="${{ env.BLUE_NAME }}"
          elif grep -q "proxy_pass http://localhost:${{ env.GREEN_PORT }};" "${{ env.NGINX_CONF }}"; then
            export ACTIVE_ENV="${{ env.GREEN_NAME }}"
          else
            echo "error: could not determine active environment" >&2
            exit 1
          fi
          echo "Active env is $ACTIVE_ENV"

          echo "Set the target environment..."
          if [ "$ACTIVE_ENV" == "blue" ]; then
            export TARGET_ENV="${{ env.GREEN_NAME }}"
            export TARGET_PORT="${{ env.GREEN_PORT }}"
            export TARGET_DIR="${{ env.GREEN_DIR }}"
          elif [ "$ACTIVE_ENV" == "green" ]; then
            export TARGET_ENV="${{ env.BLUE_NAME }}"
            export TARGET_PORT="${{ env.BLUE_PORT }}"
            export TARGET_DIR="${{ env.BLUE_DIR }}"
          else
            echo "error: could not determine target environment" >&2
            exit 1
          fi

          echo "The upcoming target environment is as follows:"
          echo "Target env: $TARGET_ENV"
          echo "Target port: $TARGET_PORT"
          echo "Target dir: $TARGET_DIR"
          
          echo "Cloning the repository..."
          rm -rf $TARGET_DIR
          mkdir -p $TARGET_DIR
          git clone ${{ env.PROJECT_REPO }} $TARGET_DIR
          echo "Repository cloned"

          echo "Writing to environment variables..." # your environment variables, if any
          echo "ENV_KEY=${{ secrets.ENV_KEY }}" >> $TARGET_DIR/.env
          echo "Environment variables written"

          echo "Install and build application..." # your install and build app stage (if any)
          cd $TARGET_DIR
          npm install
          npm run build
          echo "Dependencies installed and app built"

          echo "Start or restart application via PM2..."
          if pm2 list | grep -q "$TARGET_ENV"; then
            echo "App detected. Restarting the app..."
            pm2 restart "$TARGET_ENV" || { echo "Failed to restart app"; exit 1; }
          else
            echo "App is not started yet. Starting the app..."
            pm2 start npm --name "$TARGET_ENV" -- run start -- -p "$TARGET_PORT" || { echo "Failed to start app"; exit 1; }
          fi
          echo "Application started/restarted"

          echo "Adding delay to ensure the app is ready..."
          sleep 10s
          echo "Delay finished"

          echo "Update nginx port..."
          sudo sed -i "s|proxy_pass http://localhost:[0-9]*;|proxy_pass http://localhost:$TARGET_PORT;|" "${{ env.NGINX_CONF }}"
          sudo nginx -s reload
          echo "Nginx updated"