containerization-and-devops

Class 9 Part 2 - Reverse Proxy with Nginx

Objective

This experiment demonstrates horizontal scaling using Docker Compose with a reverse proxy (Nginx).
Multiple WordPress containers are deployed and traffic is routed through Nginx as a single entry point.

---

Architecture Overview

Browser
↓
Nginx (Port 8080)
↓
WordPress (3 Replicas)
↓
MySQL Database

This setup implements a 3-tier architecture:

• Presentation Layer → Nginx\
• Application Layer → WordPress (Scaled)\
• Database Layer → MySQL

---

docker-compose.yml

services:
  mysql:
    image: mysql:8.0
    container_name: class9_mysql
    environment:
      MYSQL_ROOT_PASSWORD: secret
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wpuser
      MYSQL_PASSWORD: wppass
    volumes:
      - mysql_data:/var/lib/mysql
    networks:
      - wordpress-network

  wordpress:
    image: wordpress:latest
    expose:
      - "80"
    environment:
      WORDPRESS_DB_HOST: mysql
      WORDPRESS_DB_USER: wpuser
      WORDPRESS_DB_PASSWORD: wppass
      WORDPRESS_DB_NAME: wordpress
    volumes:
      - wp_content:/var/www/html/wp-content
    depends_on:
      - mysql
    networks:
      - wordpress-network

  nginx:
    image: nginx:latest
    ports:
      - "8080:80"
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf
    depends_on:
      - wordpress
    networks:
      - wordpress-network

volumes:
  mysql_data:
  wp_content:

networks:
  wordpress-network:

---

nginx.conf

events {}

http {
    upstream wordpress {
        server wordpress:80;
    }

    server {
        listen 80;

        location / {
            proxy_pass http://wordpress;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
        }
    }
}

---

Scaling Command Used

docker compose up -d --scale wordpress=3

---

Output Observed

Containers Created:

• class9_mysql\
• part2-wordpress-1\
• part2-wordpress-2\
• part2-wordpress-3\
• part2-nginx-1

Docker automatically created:

• Network → part2_wordpress-network\
• Volumes → part2_mysql_data, part2_wp_content

---

Key Concepts Learned

1. Why port conflicts happen when scaling with fixed ports\
2. Difference between ports and expose\
3. Horizontal scaling using --scale\
4. Reverse proxy architecture\
5. Docker internal DNS resolution\
6. Load balancing using Nginx upstream

---

Conclusion

This experiment successfully demonstrated:

• Horizontal scaling of application containers
• Reverse proxy configuration using Nginx
• Service isolation using Docker networks
• Production-style container architecture

The system now follows a scalable multi-container design where only Nginx is publicly exposed and WordPress replicas are internally load balanced.

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