https://github.com/mohanad-80/load-balancer
A simple HTTP round robin load balancer with health checks built with Node.js and Express.
https://github.com/mohanad-80/load-balancer
expressjs load-balancer nodejs round-robin-algorithm
Last synced: 4 months ago
JSON representation
A simple HTTP round robin load balancer with health checks built with Node.js and Express.
- Host: GitHub
- URL: https://github.com/mohanad-80/load-balancer
- Owner: mohanad-80
- License: mit
- Created: 2025-06-11T13:58:14.000Z (6 months ago)
- Default Branch: main
- Last Pushed: 2025-06-26T03:38:05.000Z (5 months ago)
- Last Synced: 2025-06-26T04:29:55.174Z (5 months ago)
- Topics: expressjs, load-balancer, nodejs, round-robin-algorithm
- Language: JavaScript
- Homepage:
- Size: 12.7 KB
- Stars: 0
- Watchers: 0
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Load Balancer
A simple HTTP load balancer built with Node.js and Express. It distributes incoming requests to multiple backend servers using a round-robin algorithm and performs periodic health checks to ensure requests are only sent to healthy servers.
## Architecture Diagram
## Features
- **Round-robin load balancing** across multiple backend servers
- **Health checks** for backend servers (via `/health` endpoint)
- **Automatic failover**: unhealthy servers are skipped until healthy again
- **Detailed logging** of incoming requests and backend responses
- **Handles all HTTP methods and paths**
- **Graceful shutdown** on SIGINT
- **Persistent connections** to backends using HTTP keep-alive
- **Add relevant forward headers for proxy best practice** (client IP, protocol, host, port)
- **Sanitize the client request and response headers for security**
- **Customizable keep-alive and maxSockets settings**
- **Detailed logging for errors and useful info**
## Getting Started
### Prerequisites
- [Node.js](https://nodejs.org/) (v16 or newer recommended)
- [npm](https://www.npmjs.com/)
### Installation
1. Clone the repository:
```bash
git clone https://github.com/mohanad-80/load-balancer.git
cd load-balancer
```
2. Install dependencies:
```bash
npm install
```
### Running Backend Servers
Start multiple backend servers on different ports (e.g., 3001, 3002, 3003):
```bash
PORT=3001 node be.js
PORT=3002 node be.js
PORT=3003 node be.js
```
You can use multiple terminals or a process manager like [pm2](https://pm2.keymetrics.io/).
### Running the Load Balancer
Start the load balancer (listens on port 3000 by default):
```bash
node lb.js
```
### Usage
Send HTTP requests to the load balancer:
```bash
curl http://localhost:3000/
```
Requests will be forwarded to healthy backend servers in round-robin order.
## Project Structure
- `lb.js` - Main load balancer logic
- `be.js` - Simple backend server for testing
- `package.json` - Project metadata and dependencies
## Customization
- Edit the `servers` array in `lb.js` to add or remove backend servers.
- Adjust health check interval or timeout as needed.
- Tune keep-alive and `maxSockets` settings in the custom HTTP agent.
- Add or modify forwarded headers as needed for your environment.
## Logging
- Logs which backend server handled each request.
- Logs backend response times.
- Logs health check status changes for each backend.
- Logs errors and timeouts with details.
## License
This project is licensed under the MIT License. See [LICENSE](./LICENSE) for details.
---
**Author:** Mohanad Ahmed