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🚀 END-TO-END: NGINX LOAD BALANCER TUTORIAL

🎯 What You Will Learn

You will build:

  • A load balancer server (NGINX)

  • Multiple backend app servers (Node/Golang/Python, etc.)

  • Load balancing algorithms (round-robin, least-conn, IP-hash)

  • Health checks

  • HTTPS on load balancer

  • Logging + performance tuning

🧱 1. What is Load Balancing?

NGINX distributes incoming traffic across multiple backend servers:

Client → NGINX (Load Balancer) → App Server 1  
                                   App Server 2  
                                   App Server 3

This gives:

✔ High availability
✔ Better performance
✔ Failover if one backend crashes
✔ Scalability

🖥 2. Example Setup

We assume 3 backend servers:

Your NGINX load balancer runs on port 80/443.

You can replicate this even on a single machine.

📌 3. Install NGINX

sudo apt update
sudo apt install nginx -y

Start and enable:

sudo systemctl start nginx
sudo systemctl enable nginx

🔧 4. Create Load Balancer Config

Create a new config:

sudo nano /etc/nginx/sites-available/loadbalancer

Paste this:

upstream backend_cluster {
    server 127.0.0.1:3001;
    server 127.0.0.1:3002;
    server 127.0.0.1:3003;
}

server {
    listen 80;
    server_name example.com;

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

🔄 5. Enable Configuration

sudo ln -s /etc/nginx/sites-available/loadbalancer /etc/nginx/sites-enabled/
sudo nginx -t
sudo systemctl reload nginx

You now have a working NGINX load balancer.

⚙️ 6. Load Balancing Methods

Modify the upstream block based on algorithm.

A) Round Robin (default)

upstream backend_cluster {
    server 127.0.0.1:3001;
    server 127.0.0.1:3002;
    server 127.0.0.1:3003;
}

Traffic is evenly distributed.

B) Least Connections

upstream backend_cluster {
    least_conn;
    server 127.0.0.1:3001;
    server 127.0.0.1:3002;
    server 127.0.0.1:3003;
}

Great for long-running requests.

C) IP Hash (sticky client sessions)

upstream backend_cluster {
    ip_hash;
    server 127.0.0.1:3001;
    server 127.0.0.1:3002;
    server 127.0.0.1:3003;
}

Same client → same backend.

D) Weighted Load Balancing

upstream backend_cluster {
    server 127.0.0.1:3001 weight=5;
    server 127.0.0.1:3002 weight=3;
    server 127.0.0.1:3003 weight=1;
}

Useful when servers have different CPU/RAM strengths.

❤️ 7. Backend Health Checks

Add:

upstream backend_cluster {
    server 127.0.0.1:3001 max_fails=3 fail_timeout=10s;
    server 127.0.0.1:3002 max_fails=3 fail_timeout=10s;
    server 127.0.0.1:3003 max_fails=3 fail_timeout=10s;
}

If a server fails 3 times → NGINX automatically removes it temporarily.

🔒 8. Enable HTTPS on Load Balancer

Install Certbot:

sudo apt install certbot python3-certbot-nginx -y

Run:

sudo certbot --nginx -d example.com

It will:

✔ Install SSL
✔ Redirect HTTP → HTTPS
✔ Update NGINX config automatically

📊 9. Logs (Important for debugging)

Access logs:

tail -f /var/log/nginx/access.log

Error logs:

tail -f /var/log/nginx/error.log

🚀 10. Simple Backend Apps for Testing

Example Node.js apps:

App 1:

const http = require("http");
http.createServer((req,res)=>{
    res.end("Response from Server 3001");
}).listen(3001);

App 2:

const http = require("http");
http.createServer((req,res)=>{
    res.end("Response from Server 3002");
}).listen(3002);

App 3:

const http = require("http");
http.createServer((req,res)=>{
    res.end("Response from Server 3003");
}).listen(3003);

Now refresh your browser multiple times:

You will see:

  • Response from Server 3001

  • Response from Server 3002

  • Response from Server 3003

→ Load balancing confirmed 🎉

🚀 11. Advanced: Load Balancer + Reverse Proxy + API Gateway

If you want, I can give:

  • Rate limiting

  • JWT auth forwarding

  • Path-based routing

  • Microservices architecture

  • Caching layer

  • Sticky sessions

  • Auto-scaling architecture

🎉 Load Balancing Setup Completed!

You now have:

✔ NGINX as load balancer
✔ Multiple backend servers
✔ Health checks
✔ HTTPS
✔ Traffic distribution methods
✔ Logging + debugging
✔ Production-ready setup