📌 Introduction to Nginx as a Reverse Proxy & Load Balancer

Nginx is a powerful reverse proxy and load balancer used to improve the performance, security, and scalability of web applications.

🔹 1. Installing Nginx

1.1 Install Nginx on Linux (Ubuntu)

sudo apt update
sudo apt install -y nginx

1.2 Start and Enable Nginx

sudo systemctl start nginx
sudo systemctl enable nginx

1.3 Verify Installation

nginx -v  # Check Nginx version
systemctl status nginx  # Verify Nginx is running

✅ Nginx is now installed and running.

🔹 2. Setting Up Nginx as a Reverse Proxy

A reverse proxy forwards client requests to backend servers.

📌 Modify Nginx Configuration (/etc/nginx/sites-available/default):

server {
    listen 80;

    server_name myapp.com;

    location / {
        proxy_pass http://localhost:3000;  # Forward requests to backend
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

Apply changes:

sudo systemctl restart nginx

✅ Now, Nginx routes traffic to localhost:3000.

🔹 3. Setting Up Nginx as a Load Balancer

Load balancing distributes traffic across multiple backend servers.

📌 Modify Nginx Configuration (/etc/nginx/sites-available/default):

upstream backend_servers {
    server 192.168.1.10:3000;
    server 192.168.1.11:3000;
    server 192.168.1.12:3000;
}

server {
    listen 80;
    server_name myapp.com;

    location / {
        proxy_pass http://backend_servers;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

Apply changes:

sudo systemctl restart nginx

✅ Now, Nginx distributes traffic across backend_servers.

🔹 4. Using Different Load Balancing Methods

Modify the upstream block to use different strategies:

Load Balancing Method	Configuration
Round Robin (default)	`server backend1; server backend2;`
Least Connections	`least_conn;`
IP Hash (sticky sessions)	`ip_hash;`

Example:

upstream backend_servers {
    least_conn;  # Distribute to the server with the fewest connections
    server 192.168.1.10:3000;
    server 192.168.1.11:3000;
}

✅ Choose the best method for your application.

🔹 5. Enabling SSL with Let's Encrypt

5.1 Install Certbot for Free SSL

sudo apt install -y certbot python3-certbot-nginx

5.2 Generate SSL Certificate

sudo certbot --nginx -d myapp.com -d www.myapp.com

5.3 Auto-Renew SSL

sudo crontab -e

Add this line:

0 0 1 * * certbot renew --quiet

✅ Now, SSL is enabled for your site.

📌 Conclusion

Nginx provides reverse proxying, load balancing, and SSL termination, making it essential for scalable, high-performance applications. 🚀

Nginx Load Balancing & Reverse Proxy