market-data-service/src/server.js

const app = require('./app');
const { testConnection } = require('./config/database');
const logger = require('./utils/logger');
const { createServer } = require('http');
const { Server } = require('socket.io');

const PORT = process.env.PORT || 3000;

// Test database connection and start server
const startServer = async () => {
  try {
    // Test database connection
    await testConnection();

    // Create HTTP server
    const server = createServer(app);

    // Initialize Socket.io
    const io = new Server(server, {
      cors: {
        origin: process.env.CORS_ORIGIN || "*",
        methods: ["GET", "POST"],
        credentials: true
      }
    });

    // Socket.io connection handling
    io.on('connection', (socket) => {
      logger.info(`Client connected: ${socket.id}`);

      // Handle subscription to symbols
      socket.on('subscribe', (symbols) => {
        if (Array.isArray(symbols)) {
          symbols.forEach(symbol => {
            socket.join(`symbol:${symbol}`);
            logger.info(`Client ${socket.id} subscribed to ${symbol}`);
          });
        } else {
          socket.join(`symbol:${symbols}`);
          logger.info(`Client ${socket.id} subscribed to ${symbols}`);
        }
      });

      // Handle unsubscription
      socket.on('unsubscribe', (symbols) => {
        if (Array.isArray(symbols)) {
          symbols.forEach(symbol => {
            socket.leave(`symbol:${symbol}`);
            logger.info(`Client ${socket.id} unsubscribed from ${symbol}`);
          });
        } else {
          socket.leave(`symbol:${symbols}`);
          logger.info(`Client ${socket.id} unsubscribed from ${symbols}`);
        }
      });

      // Handle disconnect
      socket.on('disconnect', () => {
        logger.info(`Client disconnected: ${socket.id}`);
      });
    });

    // Make io accessible to routes/controllers
    app.set('io', io);

    // Start the server
    server.listen(PORT, () => {
      logger.info(`Market Data Service is running on port ${PORT}`);
      logger.info(`Environment: ${process.env.NODE_ENV || 'development'}`);
      logger.info(`Health check available at: http://localhost:${PORT}/health`);
      logger.info(`WebSocket server ready for connections`);
    });

    // Graceful shutdown
    process.on('SIGTERM', () => {
      logger.info('SIGTERM received, shutting down gracefully');
      server.close(() => {
        logger.info('Process terminated');
        process.exit(0);
      });
    });

    process.on('SIGINT', () => {
      logger.info('SIGINT received, shutting down gracefully');
      server.close(() => {
        logger.info('Process terminated');
        process.exit(0);
      });
    });

  } catch (error) {
    logger.error('Failed to start server:', error);
    process.exit(1);
  }
};

// Handle uncaught exceptions
process.on('uncaughtException', (error) => {
  logger.error('Uncaught Exception:', error);
  process.exit(1);
});

// Handle unhandled promise rejections
process.on('unhandledRejection', (reason, promise) => {
  logger.error('Unhandled Rejection at:', promise, 'reason:', reason);
  process.exit(1);
});

startServer();