Nginx as a Load Balancer

Configure the servers

You need to have node preinstalled in your system or you can use any server of your choice.

Our server running on the following sockets:

• localhost:3000

• localhost:3001

• localhost:3002

I will be creating 3 simple node servers running on my local machine.

Run npm init in your root project directory.

Then create three files server_1.js, server_2.js, server_3.js.

Here is what my project directory will look like.

.
├── package.json
├── server_1.js
├── server_2.js
└── server_3.js

Here is the code for server_1.js

const http = require('http');

const hostname = '127.0.0.1';
const port = 3000;

const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/html');
  res.end('<h1>Hello from - server_1</h1>\n');
});

server.listen(port, hostname, () => {
  console.log(`Server running at http://${hostname}:${port}/`);
});

Run node server_1.js for starting this server on 3000.

Here is the code for server_2.js

const http = require('http');

const hostname = '127.0.0.1';
const port = 3001;

const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/html');
  res.end('<h1>Hello from - server_2</h1>\n');
});

server.listen(port, hostname, () => {
  console.log(`Server running at http://${hostname}:${port}/`);
});

Open a new terminal and run node server_1.js for starting this server on 3001.

Here is the code for server_3.js

const http = require('http');

const hostname = '127.0.0.1';
const port = 3002;

const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/html');
  res.end('<h1>Hello from - server_3</h1>\n');
});

server.listen(port, hostname, () => {
  console.log(`Server running at http://${hostname}:${port}/`);
});

Open a new terminal and run node server_3.js for starting this server on 3002.

Configure Nginx

If you want to install Nginx from the source code, please follow the guideline of this article https://techblog.akashojha.com/install-nginx-from-source-code

If you already running Nginx, first you need to stop it.

sudo systemctl stop nginx

Now let's add a new file load_balancer.conf in /etc/nginx directory.

sudo vim /etc/nginx/load_balancer.conf

Let's add the following content in your load_balancer.conf file.

events {
}

http {
    upstream nodeapis {
        server localhost:3000;
        server localhost:3001;
        server localhost:3002;
    }
    server{
        listen 8888;

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

Let's start your Nginx server.

sudo nginx -c /etc/nginx/load_balancer.conf

If you go to your terminal and run the following command

while sleep 0.5; do curl http://localhost:8888/; done;

You should be able to see the response like this in the terminal

<h1>Hello from - server_2</h1>
<h1>Hello from - server_3</h1>
<h1>Hello from - server_1</h1>
<h1>Hello from - server_2</h1>
<h1>Hello from - server_3</h1>
<h1>Hello from - server_1</h1>
<h1>Hello from - server_2</h1>
<h1>Hello from - server_3</h1>
<h1>Hello from - server_1</h1>
<h1>Hello from - server_2</h1>
<h1>Hello from - server_3</h1>
<h1>Hello from - server_1</h1>
<h1>Hello from - server_2</h1>
<h1>Hello from - server_3</h1>

This is following the round-robin method i.e., choose from all the local servers with equal priority.

You can go to your browser and open http://127.0.0.1:8888 and see the same response by reloading the server again and again.

So, we have learnt how to use Nginx as a load balancer.

Happy Learning!!