Scalable WebSocket Server With Redis

This project demonstrates how to scale Golang WebSocket servers horizontally using:

• 🧠 Go + Fiber + Fiber WebSocket for services backbone
• 🔁 Redis Pub/Sub for cross-instance communication
• 🔀 NGINX as a reverse proxy and load balancer
• 🐳 Docker Compose to run services locally

🚀 Project Purpose

WebSocket servers maintain persistent client connections, but when scaled horizontally, each instance handles its own isolated connections. This creates a challenge: messages can't reach clients connected to other instances:

❗ Messages sent from Instance A will not reach clients connected to Instance B

This project solves that problem using Redis Pub/Sub, which allows different server instances to communicate and broadcast messages across all connected clients, regardless of which server they are connected to.

The project demonstrates:

• How to scale WebSocket servers horizontally
• How to use Redis for message broadcasting between instances
• How to implement a load-balanced WebSocket endpoint using NGINX

Features

• WebSocket server with Json message handling
• Load balancing with Nginx
• Cross-instance message broadcasting via Redis Pub/Sub
• Easily extensible for authentication, channels, presence, etc.

Requirements

• Docker + Docker Compose
• Go (only for local binary build)

Build Instructions

1. Clone the Repository

git clone https://github.com/virakthaka/go-websocket-scale-with-redis.git
cd go-websocket-scale-with-redis

2. Build the Go App Binary

GOOS=linux GOARCH=amd64 go build -o bin/app

This generates a binary at bin/app that will be used inside Docker containers.

🐳 Run the Services in Docker

docker-compose up -d --build

Action command:

• Build App binary image
• Start Redis and Nginx Server
• Start two app instances (app1, app2)
• Start Endpoint ws://localhost:8080/ws/:room

Structure

src/
├── main.go              # Go WebSocket server
│── go.mod
├── views/
│   └── index.html       # Chat UI portal connect to websocket  
│── bin/app              # Compiled Go binary (built manually)
├── nginx/
│   └── default.conf     # NGINX config for load balancing
├── docker-compose.yml
├── Dockerfile           # For docker image Go service

Testing

Option 1: Using Postman

Connect two postman tabs:

ws://localhost:8080/ws/room1
ws://localhost:8080/ws/room2

Send a message in one, and you'll receive it in both!

{
  "sender":"Alice",
  "content":"Hello everyone!"
}

Option 2: Browser Client

Create a simple index.html and open it in two tabs:

<input id="name" placeholder="Input your name" />
<input id="input" placeholder="Type a message..." />
<button onclick="send()">Send</button>
<pre id="log"></pre>

<script>
  const ws = new WebSocket("ws://localhost:8080/ws/room1");

  ws.onopen = () => log("Connected");
  ws.onclose = () => log("Disconnected");
  ws.onmessage = (msg) => log(msg.data);

  function send() {
    const msg = document.getElementById("input").value;
    const sender = document.getElementById("name").value;
    const json = JSON.stringify({ sender: sender, content: msg });
    ws.send(json);
  }

  function log(msg) {
    document.getElementById("log").textContent += msg + "\n";
  }
</script>

Or simply to open http://localhost:8080/chat/64d018-6ec-802-ad7-e65e41

License

This project is open-source and available under the MIT License.