Stock Exchange API

A real-time stock price streaming application built with Spring Boot, WebSocket/STOMP, and RabbitMQ. This API simulates a stock exchange by generating and broadcasting live stock price updates to connected clients.

🎯 Purpose

The Stock Exchange API provides:

• Real-time stock price updates for 10 major tech stocks (AAPL, GOOGL, MSFT, TSLA, AMZN, NVDA, META, NFLX, AMD, INTC)
• WebSocket/STOMP messaging for instant price delivery to clients
• Multi-instance scalability using RabbitMQ as a message broker
• Historical price data stored in PostgreSQL (in this example Azure Cosmos DB for PostgreSQL)
• Horizontal scaling support for handling millions of concurrent connections

🏗️ Architecture

┌─────────────┐         WebSocket/STOMP          ┌──────────────────┐
│   Browser   │◄──────────────────────────────►  │  Spring Boot App │
│   Clients   │     /ws or /ws-stomp             │  (Container App) │
└─────────────┘                                  └──────────────────┘
                                                          │
                                                          │ STOMP/TCP
                                                          │ Port 61613
                                                          ▼
                                                  ┌──────────────────┐
                                                  │    RabbitMQ      │
                                                  │ (Message Broker) │
                                                  └──────────────────┘
                                                          │
                                                          │ Persist
                                                          ▼
                                                  ┌──────────────────┐
                                                  │   Cosmos DB      │
                                                  │   (PostgreSQL)   │
                                                  └──────────────────┘

🚀 Entry Points

WebSocket Endpoints

The API exposes WebSocket endpoints for real-time communication:

Endpoint	Protocol	Description
/ws	WebSocket + SockJS	Primary endpoint with fallback support
/ws-stomp	WebSocket + STOMP	Alternative STOMP endpoint

Full URL Example:

https://{host_name}:{local_port}/ws

REST Endpoints (Optional)

Endpoint	Method	Description
/api/stocks/current	GET	Get current prices for all stocks
/api/stocks/{symbol}	GET	Get current price for specific stock

📡 Using from the Browser

Quick Start with JavaScript

// 1. Connect to WebSocket endpoint
const socket = new SockJS('https://{host_name}:{local_port}/ws');
const stompClient = Stomp.over(socket);

// 2. Establish connection
stompClient.connect({}, function(frame) {
    console.log('Connected:', frame);
    
    // 3. Subscribe to stock updates
    // Subscribe to ALL stocks
    stompClient.subscribe('/exchange/amq.topic/stock.*', function(message) {
        const stockPrice = JSON.parse(message.body);
        console.log('Received:', stockPrice);
        updateUI(stockPrice);
    });
    
    // Or subscribe to specific stock
    stompClient.subscribe('/exchange/amq.topic/stock.AAPL', function(message) {
        const stockPrice = JSON.parse(message.body);
        console.log('AAPL:', stockPrice);
    });
});

Message Format

Each stock price update contains:

{
  "id": 12345,
  "symbol": "AAPL",
  "price": 175.50,
  "change": 2.30,
  "changePercent": 1.33,
  "dayHigh": 176.80,
  "dayLow": 173.20,
  "openPrice": 174.00,
  "previousClose": 173.20,
  "volume": 5234567,
  "timestamp": "2025-12-22T14:30:00Z"
}

🎨 Demo UI - index.html

The included index.html file serves as a live demonstration dashboard for the Stock Exchange API. It showcases real-time WebSocket connectivity and provides an interactive interface for monitoring stock prices.

Features

• Real-time Price Display: Shows live updates for all 10 stocks in a responsive grid layout
• WebSocket Connection Management: Connect/Disconnect buttons with visual status indicators
• SockJS Fallback Support: Automatically handles browsers that don't support native WebSocket
• STOMP Protocol: Uses STOMP over WebSocket for reliable message delivery
• Visual Indicators: Color-coded price changes (green for up, red for down)
• Stock Details: Displays high/low prices, volume, and last update time
• Message Counter: Tracks the number of real-time updates received

Usage

1. Open index.html in any modern web browser
2. Replace {host_name}:{local_port} with your actual host and port's App
3. Click "Connect" to establish WebSocket connection
4. Watch as stock prices update in real-time (every second)

The demo file requires no server installation and connects directly to your deployed Stock Exchange API, making it perfect for testing and demonstrations.

🔌 Subscription Patterns

Subscribe to All Stocks (Recommended)

stompClient.subscribe('/exchange/amq.topic/stock.*', callback);

Subscribe to Specific Stock

stompClient.subscribe('/exchange/amq.topic/stock.AAPL', callback);

Subscribe to Multiple Stocks

const symbols = ['AAPL', 'GOOGL', 'MSFT'];
symbols.forEach(symbol => {
    stompClient.subscribe(`/exchange/amq.topic/stock.${symbol}`, callback);
});

Subscribe with Pattern Matching

// Subscribe to stocks starting with 'A'
stompClient.subscribe('/exchange/amq.topic/stock.A*', callback);

🛠️ Configuration

Environment Variables

Variable	Description	Default
SPRING_DATASOURCE_URL	PostgreSQL connection string	jdbc:postgresql://localhost:5432/stockdb
SPRING_DATASOURCE_USERNAME	Database username	dbadmin
SPRING_DATASOURCE_PASSWORD	Database password	password
RABBITMQ_STOMP_ENABLED	Enable RabbitMQ broker	true
RABBITMQ_HOST	RabbitMQ hostname	localhost
RABBITMQ_STOMP_PORT	RabbitMQ STOMP port	61613
RABBITMQ_USERNAME	RabbitMQ username	stockadmin
RABBITMQ_PASSWORD	RabbitMQ password	StockExchange2024!

Application Properties

stock-exchange:
  update-interval: 1000        # Price update frequency (ms)
  volatility: 0.02             # Price change volatility (2%)
  symbols: AAPL,GOOGL,MSFT,TSLA,AMZN,NVDA,META,NFLX,AMD,INTC

📦 Deployment to the Azure Container App (it might be used different cloud services, not only Azure)

Azure Container Apps

# Get your Container App URL
az containerapp show \
  --name stock-exchange-api \
  --resource-group stock-exchange-rg \
  --query "properties.configuration.ingress.fqdn" \
  --output tsv

# View logs
az containerapp logs show \
  --name stock-exchange-api \
  --resource-group stock-exchange-rg \
  --follow

Scaling

The application automatically scales based on:

• Min replicas: 2 (always-on for high availability)
• Max replicas: 10 (scales up under load)
• RabbitMQ: Distributes messages across all instances

🧪 Testing

Using Browser Console

Open browser console (F12) and run:

const socket = new SockJS('https://your-app-url.azurecontainerapps.io/ws');
const stompClient = Stomp.over(socket);

stompClient.connect({}, function() {
    console.log('Connected!');
    stompClient.subscribe('/exchange/amq.topic/stock.*', function(msg) {
        console.log('Update:', JSON.parse(msg.body));
    });
});

Using cURL (REST endpoints)

# Get all current prices
curl https://your-app-url.azurecontainerapps.io/api/stocks/current

# Get specific stock
curl https://your-app-url.azurecontainerapps.io/api/stocks/AAPL

📊 Monitoring

Check RabbitMQ Management UI

http://rabbitmq-stomp-broker.eastus.azurecontainer.io:15672
Username: stockadmin
Password: StockExchange2024!

View Active Connections

Check the "Connections" tab in RabbitMQ Management UI to see:

• Connected Spring Boot instances
• Active STOMP sessions
• Message rates and throughput

🔒 Security Considerations

For production deployments:

1. Enable HTTPS/WSS for WebSocket connections
2. Implement authentication/authorization
3. Use Azure Key Vault for secrets
4. Configure CORS properly for your domain
5. Enable rate limiting
6. Use Azure Application Gateway for DDoS protection

🤝 Dependencies

• Spring Boot 3.x - Application framework
• Spring WebSocket - WebSocket support
• Spring STOMP - STOMP protocol
• RabbitMQ - Message broker
• PostgreSQL - Database (Azure Cosmos DB)
• SockJS - WebSocket fallback (client-side)
• STOMP.js - STOMP client (browser)

📝 License

This project is for demonstration purposes.

🆘 Troubleshooting

Connection Issues

1. Can't connect from browser

   • Verify Container App is running
   • Check ingress is enabled and external
   • Ensure /ws endpoint is accessible

2. No price updates received

   • Check RabbitMQ container is running
   • Verify RabbitMQ STOMP plugin is enabled
   • Check subscription path is correct: /exchange/amq.topic/stock.*

3. "Invalid destination" errors

   • Ensure using /exchange/amq.topic/ prefix
   • Check RabbitMQ configuration in application.yml
   • Verify STOMP relay is properly configured

Debugging

Enable debug logging in browser console:

stompClient.debug = function(str) {
    console.log('STOMP:', str);
};

📧 Support

For issues or questions, check the Azure Container Apps logs:

az containerapp logs show \
  --name stock-exchange-api \
  --resource-group stock-exchange-rg \
  --follow