Back to Engineering Notes
100 Days of DevOpsEngineering Note

Install and Configure Nginx as an LBR

Configure Nginx as a Load Balancer to distribute incoming traffic across multiple backend servers for:

🎯 Objective

Configure Nginx as a Load Balancer to distribute incoming traffic across multiple backend servers for:

⚡ Better performance
🔁 High availability
📈 Scalability
🛡 Fault tolerance

# 📜 What is a Load Balancer?

A Load Balancer distributes client requests across multiple servers.

Example:

plain text
Client Request
      │
      ▼
   Nginx LBR
   ┌────┼────┐
   ▼    ▼    ▼
App1  App2  App3

Benefits:

# 1️⃣ Install Nginx

Ubuntu / Debian

plain text
sudo apt update
sudo apt install nginx-y

RHEL / CentOS / Amazon Linux

plain text
sudo yum install nginx -y

Start service:

plain text
sudo systemctl start nginx
sudo systemctl enable nginx

Check status:

plain text
sudo systemctl status nginx

# 2️⃣ Configure Backend Servers

Example backend servers:

These servers run the application (Apache, Node.js, Tomcat, etc.).

# 3️⃣ Configure Nginx Load Balancer

Edit configuration:

plain text
sudo nano /etc/nginx/nginx.conf

Add upstream block:

plain text
http {

    upstream backend_servers {
        server 10.0.0.11;
        server 10.0.0.12;
        server 10.0.0.13;
    }

    server {
        listen 80;

        location / {
            proxy_pass http://backend_servers;
        }
    }
}

# 4️⃣ Test Configuration

plain text
sudo nginx -t

Expected output:

plain text
syntax is ok
test is successful

# 5️⃣ Reload Nginx

plain text
sudo systemctl reload nginx

# 6️⃣ Test Load Balancing

Send multiple requests:

plain text
curl http://your-server-ip

You should see responses from different backend servers.

# 7️⃣ Load Balancing Methods

Nginx supports multiple algorithms.

1️⃣ Round Robin (Default)

plain text
Request 1 → Server1
Request 2 → Server2
Request 3 → Server3

Configuration:

plain text
upstream backend_servers {
    server 10.0.0.11;
    server 10.0.0.12;
}

2️⃣ Least Connections

Send traffic to server with least active connections.

plain text
upstream backend_servers {
    least_conn;
    server 10.0.0.11;
    server 10.0.0.12;
}

3️⃣ IP Hash

Same user always goes to the same server.

plain text
upstream backend_servers {
    ip_hash;
    server 10.0.0.11;
    server 10.0.0.12;
}

Useful for session persistence.

# 8️⃣ Add Health Checks

Mark failed server:

plain text
upstream backend_servers {
    server 10.0.0.11 max_fails=3 fail_timeout=30s;
    server 10.0.0.12 max_fails=3 fail_timeout=30s;
}

If a server fails 3 times within 30 seconds, it is removed temporarily.

# 🧠 Architecture Example

plain text
Internet
               │
               ▼
        Nginx Load Balancer
               │
     ┌─────────┼─────────┐
     ▼         ▼         ▼
 App Server1 App Server2 App Server3

# 🧪 Troubleshooting

Check Nginx status

plain text
sudo systemctl status nginx

View logs

plain text
sudo tail-f /var/log/nginx/error.log

Test configuration

plain text
sudo nginx-t

# ✅ Summary