Discord Stream Backend

Note: This project was built as part of the Railway Senior Full-Stack Engineer - Support application. The assignment: "Build a Discord bot that streams messages from a Discord channel into a web front-end, with a backend component."

A robust Socket.IO backend for real-time Discord message streaming with authentication, rate limiting, and comprehensive error handling.

Features

• 🔐 JWT Authentication - Secure user authentication with token-based sessions
• 📡 Socket.IO Integration - Real-time bidirectional communication
• 🤖 Discord Bot Integration - Seamless Discord API integration
• 🏥 Health Monitoring - Comprehensive health checks and metrics
• 🔒 Security - Helmet.js security headers and CORS protection
• 📊 Metrics - Real-time connection and performance metrics
• 🛡️ Error Handling - Comprehensive error handling and logging

Tech Stack

• Runtime: Node.js with TypeScript
• Web Framework: Express.js
• Real-time: Socket.IO
• Discord: discord.js library
• Security: Helmet.js, CORS, JWT
• Monitoring: Custom health checks and metrics

Quick Start

Prerequisites

• Node.js 18+
• MySQL 8.0+
• Redis 6.0+
• Discord Bot Token

Installation

1. Clone and install dependencies:

   npm install

2. Set up environment variables:

   cp env.example .env
   # Edit .env with your configuration

3. Start the server:

   # Development
   npm run dev
   
   # Production
   npm run build
   npm start

API Endpoints

Health Checks

• GET /api/health - Server health status
• GET /api/metrics - Real-time metrics
• GET /api/status - Detailed server status
• GET /api/ready - Load balancer readiness
• GET /api/live - Liveness probe

Socket.IO Events

Client to Server

• get_channels - Fetch user's available channels
• join_channel - Join a Discord channel
• leave_channel - Leave a Discord channel

Server to Client

• channels_list - Available channels
• user_info - User information
• message - New message received
• message_update - Message edited
• message_delete - Message deleted
• messages_bulk - Message history
• channel_update - Channel information
• error - Error notification
• rate_limited - Rate limit exceeded

Example Payloads

message (Server → Client)

{
  "id": "123456789",
  "content": "Hello, world!",
  "author": {
    "id": "987654321",
    "username": "Alice"
  },
  "timestamp": "2024-01-01T12:00:00.000Z",
  "channelId": "123456789",
  "serverId": "111222333"
}

join_channel (Client → Server)

{
  "channelId": "123456789"
}

channels_list (Server → Client)

[
  {
    "id": "123456789",
    "name": "general",
    "type": "text",
    "serverId": "111222333"
  }
]

This repository contains only the backend service. The frontend should connect to the backend via Socket.IO, authenticate with a JWT, and display messages in real time. If you need a reference implementation, see https://discord-bot.vercel.app (replace with your actual repo if available).

Development

Scripts

# Development
npm run dev          # Start with nodemon
npm run build        # Build TypeScript
npm start           # Start production server
npm test            # Run tests
npm run lint        # Lint code
npm run lint:fix    # Fix linting issues

Project Structure

backend/
├── src/
│   ├── handlers/          # Socket.IO event handlers
│   ├── middleware/        # Authentication & error handling
│   ├── namespaces/        # Socket.IO namespace setup
│   ├── routes/           # HTTP API routes
│   ├── services/         # Business logic services
│   ├── utils/            # Database, rate limiting utilities
│   ├── types.ts          # TypeScript type definitions
│   └── server.ts         # Main server file
├── tests/               # Test files
├── package.json
├── tsconfig.json
├── env.example
└── README.md

Monitoring

Health Check Response

{
  "status": "healthy",
  "timestamp": "2024-01-01T12:00:00.000Z",
  "uptime": 3600,
  "connections": {
    "total": 150,
    "discord": 45
  },
  "memory": {
    "used": "45MB",
    "total": "128MB"
  },
  "environment": "production"
}

Metrics Response

{
  "connections": {
    "total": 150,
    "discord": 45
  },
  "rooms": {
    "total": 25,
    "channels": 15,
    "activeChannels": [
      {
        "channelId": "123456789",
        "userCount": 5
      }
    ]
  },
  "performance": {
    "eventLoopDelay": 123456789n,
    "cpuUsage": {
      "user": 123456,
      "system": 789012
    }
  }
}

Testing

This project includes unit tests for authentication, message handling, and error handling. To run tests:

npm test

Design Decisions

• Socket.IO is used for real-time streaming and channel-based rooms, allowing efficient message delivery to only those users who have joined a channel.
• JWT provides secure, stateless authentication for all socket connections.
• Modular code structure makes it easy to extend the backend with new features, events, or integrations.
• Health and metrics endpoints are included for easy deployment monitoring and observability.

Deployment

Docker

FROM node:18-alpine

WORKDIR /app

COPY package*.json ./
RUN npm ci --only=production

COPY . .
RUN npm run build

EXPOSE 3001

HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
  CMD curl -f http://localhost:3001/api/health || exit 1

CMD ["npm", "start"]

Docker Compose

version: '3.8'

services:
  discord-backend:
    build: .
    ports:
      - "3001:3001"
    environment:
      - NODE_ENV=production
      - DATABASE_URL=mysql://postgres:password@db:5432/discord_stream
      - REDIS_URL=redis://redis:6379
    depends_on:
      - db
      - redis
    restart: unless-stopped

  db:
    image: mysql:8.0
    environment:
      - MYSQL_DATABASE=discord_stream
      - MYSQL_ROOT_PASSWORD=password
    volumes:
      - mysql_data:/var/lib/mysql
    restart: unless-stopped

  redis:
    image: redis:7-alpine
    volumes:
      - redis_data:/data
    restart: unless-stopped

volumes:
  mysql_data:
  redis_data:

Security

• JWT Authentication - Secure token-based authentication
• CORS Protection - Configurable CORS policies
• Helmet.js - Security headers and CSP
• Input Validation - Message content validation
• Error Handling - Comprehensive error logging

Performance

• Socket.IO Optimization - Configurable ping/pong intervals
• Memory Management - Proper cleanup on disconnect
• Graceful Shutdown - Clean resource cleanup

Troubleshooting

Common Issues

1. Discord Bot Not Connecting

   • Verify bot token is correct
   • Check bot has required permissions
   • Ensure bot is added to servers

2. Socket.IO Connection Issues

   • Verify CORS configuration
   • Check authentication token
   • Ensure frontend URL is correct

Logs

The server provides detailed logging:

• 🔐 - Authentication events
• 🔗 - Connection events
• 📨 - Message events
• 👥 - Channel join/leave events
• 📊 - Statistics and metrics
• ❌ - Error events
• ✅ - Success events

Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests if applicable
5. Submit a pull request

License

MIT License - see LICENSE file for details.