🚀 Nginx Reverse Proxy & Load Balancing with Node.js (Dockerized)

This repository demonstrates a production-style architecture using:

• Node.js (Express)
• Nginx as Reverse Proxy
• Horizontal Scaling (Multiple Instances)
• Docker & Docker Compose
• Load Testing using Autocannon

The goal of this project is to deeply understand:

• How Nginx works as a reverse proxy
• How Docker networking works
• How horizontal scaling improves performance
• How failover behaves when instances go down
• When to rebuild images vs reuse containers

---

🏗 Architecture

Development Mode (Multi-instance + Nginx)

Client
   ↓
Nginx (port 8000)
   ↓
app1 | app2 | app3 (Node containers)

Nginx distributes traffic across multiple Node instances.

---

📦 Tech Stack

• Node.js 22 (Alpine)
• Express
• Nginx
• Docker
• Docker Compose
• Nodemon (dev only)
• Autocannon (load testing)

---

🧠 Key Concepts Demonstrated

• Reverse proxy configuration
• Docker internal networking
• Service name DNS resolution
• Horizontal scaling
• Failover testing
• Dev vs Production Docker setups
• Load testing and performance comparison

---

📁 Project Structure

.
├── app.js
├── package.json
├── Dockerfile
├── Dockerfile.dev
├── docker-compose.dev.yml
├── docker-compose.prod.yml
├── nginx.conf
└── README.md

---

⚙️ Setup & Installation

1️⃣ Clone the Repository

git clone <your-repo-url>
cd ngnixprac

---

🧪 Development Mode (With Nginx + 3 Instances)

Start the development environment:

npm run docker:dev

If you changed dependencies or Dockerfile:

npm run docker:dev:build

To stop everything:

npm run docker:dev:down

---

🌐 Access Application

http://localhost:8000

Each refresh should show different INSTANCE_ID, proving load balancing works.

Example response:

{
  "message": "Node js server running ngnix 🚀🚀🚀",
  "instance": "2"
}

---

🏭 Production Mode (Single Container)

Start production container:

npm run docker:prod

Access:

http://localhost:3000

Production image:

• No nodemon
• Uses npm install --production
• Restart policy enabled

---

🐳 Docker Commands Explained

Start environment

docker compose up

Rebuild image

docker compose up --build

Stop & remove containers

docker compose down

Stop specific service

docker compose stop app1

---

🧪 Load Testing

Install autocannon globally (optional):

npm install -g autocannon

Test via Nginx:

npx autocannon -c 100 -d 15 http://localhost:8000

Test direct Node:

npx autocannon -c 100 -d 15 http://localhost:3000

---

📊 Scaling Experiment

With 1 instance:

• ~13k req/sec (baseline)

With 3 instances:

• Near-linear scaling under Nginx

Stop one container during load:

docker compose -f docker-compose.dev.yml stop app2

Observe:

• Traffic reroutes automatically
• System remains operational
• Throughput decreases proportionally

---

🔍 Nginx Reverse Proxy Config

events {}

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

    server {
        listen 80;

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

---

🧠 Key Learnings

• localhost inside Docker refers to the container itself
• Docker services communicate via internal DNS
• Horizontal scaling improves throughput
• Nginx handles connection management efficiently
• docker compose up vs up --build
• Dev vs Production image separation

---

🚀 Ngnix is Awesome! 🚀

This repository demonstrates practical backend infrastructure knowledge including:

• Reverse proxy architecture
• Container orchestration fundamentals
• Load balancing
• High availability testing
• Performance benchmarking