Week 2 Day 5: Mini Project - Static Site with Load Balancing

Today we will simulate Horizontal Scaling on your laptop using Docker. We will run 3 instances of a web server and put Nginx in front as a Load Balancer.

Requirements

Docker Installed.

1. Create a Simple Server (`app.js`)

We want to know which server is responding.

const express = require('express');
const app = express();
const ID = Math.floor(Math.random() * 1000);

app.get('/', (req, res) => {
    res.send(`Hello from Server ID: ${ID}`);
});

app.listen(3000, () => console.log(`Running on 3000, ID: ${ID}`));

2. Dockerfile

FROM node:18
WORKDIR /app
COPY package.json .
RUN npm install
COPY . .
CMD ["node", "app.js"]

3. Nginx Config (`nginx.conf`)

Configure Nginx to define an upstream group of servers.

events {}
http {
    upstream backend {
        server app1:3000;
        server app2:3000;
        server app3:3000;
    }

    server {
        listen 80;
        location / {
            proxy_pass http://backend;
        }
    }
}

4. Docker Compose (`docker-compose.yml`)

Spin it all up!

version: '3'
services:
  app1:
    build: .
  app2:
    build: .
  app3:
    build: .
  lb:
    image: nginx
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf
    ports:
      - "8080:80"

5. Test It

Run docker-compose up. Open http://localhost:8080. Refresh multiple times. You should see:

“Hello from Server ID: 123”
“Hello from Server ID: 456”
“Hello from Server ID: 789”

Congratulations! You just built a horizontally scaled architecture. 🏗️ Next week: Databases. Storing data safely at scale.

Next Step

Next: Relational Vs Nosql →