Distributed WebSocket System

This project demonstrates a distributed WebSocket system with load balancing, multiple WebSocket servers, and a Redis-based message broker. The system is containerized using Docker and includes a client application built with Angular.

Architecture

The system consists of the following components:

1. WebSocket Servers (2 instances)

   • Node.js-based WebSocket servers
   • Each server has a unique ID
   • Uses Redis for message broadcasting between servers
   • Handles WebSocket connections and message routing

2. Load Balancer (Nginx)

   • Distributes WebSocket connections across multiple servers
   • Provides high availability and scalability
   • Configured for WebSocket protocol support

3. Redis

   • Acts as a message broker between WebSocket servers
   • Enables real-time message broadcasting across all server instances
   • Persists data using a Docker volume

4. Client Application (Angular)

   • Modern web interface for interacting with the WebSocket system
   • Real-time message display and interaction
   • Responsive design

Prerequisites

• Docker and Docker Compose
• Node.js (for local development)
• Angular CLI (for local client development)

Getting Started

1. Clone the repository

   git clone https://github.com/logeshkannan96/distributed-websockets.git
   cd distributed-websocket

2. Start the system using Docker Compose

   docker-compose up --build

   This will start:

   • Two WebSocket server instances
   • Nginx load balancer
   • Redis server
   • The client application will be available at http://localhost:4200

3. For local development

   Server Development:

   cd server
   npm install
   npm run dev

   Client Development:

   cd client
   npm install
   ng serve

Configuration

WebSocket Servers

• Server instances are configured through environment variables in docker-compose.yaml
• Each server has a unique SERVER_ID
• Redis connection is configured via REDIS_URL

Load Balancer

• Nginx configuration is located in lb/nginx.conf
• Load balancing strategy can be modified in the configuration file

Redis

• Redis runs on the default port 6379
• Data persistence is configured through Docker volumes

Testing the System

1. Open multiple browser windows to http://localhost:4200
2. Connect to the WebSocket server
3. Send messages from different clients
4. Observe how messages are broadcasted across all connected clients
5. Verify that the load balancer distributes connections across both server instances

Monitoring

• Redis data can be monitored using Redis CLI:

  docker exec -it distributed-websocket_redis_1 redis-cli

• Server logs can be viewed using:

  docker-compose logs -f websocket-server-1
  docker-compose logs -f websocket-server-2

Troubleshooting

1. Connection Issues

   • Verify all containers are running: docker-compose ps
   • Check server logs for errors
   • Ensure Redis is accessible from WebSocket servers

2. Load Balancer Issues

   • Check Nginx configuration
   • Verify WebSocket server health
   • Check Nginx logs: docker-compose logs nginx

Contributing

1. Fork the repository
2. Create a feature branch
3. Commit your changes
4. Push to the branch
5. Create a Pull Request

API Usage

Sending Messages

You can send messages to the WebSocket system using the REST API endpoint. Here are some examples:

1. Send a message using curl:

   curl --location 'http://localhost/api/send-message' \
   --header 'Content-Type: application/json' \
   --data '{
       "username": "kattappa",
       "message": "Swami, I have a confession to make"
   }'

2. Send a message with different content:

   curl --location 'http://localhost/api/send-message' \
   --header 'Content-Type: application/json' \
   --data '{
       "username": "bahubali",
       "message": "Kattappa, yes tell me"
   }'

The API accepts POST requests with the following JSON structure:

{
    "username": "string",
    "message": "string"
}

Note: A similar implementation using Server-Sent Events (SSE) with Redis Pub/Sub is available in the following GitHub repository: 👉 logeshkannan96/sse-redispubsub Feel free to check it out for reference or inspiration.