Production Express.js: Enterprise MVC Architecture, Hardened Security, and Rate Limiting (Part 3)

// 1. ISOLATED CONTROLLER MODULE: labController.js
// The Controller reads incoming parameters, interacts with the data model, and sends the response payload
const LabModel = {
  async fetchActiveInventory() {
    return [
      { id: 201, name: "Cisco Systems Rack A", wing: "Network Lab", online: true },
      { id: 202, name: "Distributed Cluster Node B", wing: "Cloud Wing", online: false }
    ];
  }
};

exports.getSystemHardwareMetrics = async (req, res, next) => {
  try {
    console.log(`[${new Date().toLocaleTimeString()}] Controller executing database inventory aggregation sequence...`);
    const hardwarePayload = await LabModel.fetchActiveInventory();
    
    res.status(200).json({
      status: "success",
      requestedBy: "Puneet Tiwari",
      results: hardwarePayload.length,
      data: { hardware: hardwarePayload }
    });
  } catch (error) {
    // Forward any unexpected execution errors down into the centralized global error gateway
    next(error);
  }
};


// 2. CLEAN ROUTING INDEX: labRouter.js
// const express = require('express');
// const router = express.Router();
// const labController = require('./labController');
//
// router.get('/hardware-metrics', labController.getSystemHardwareMetrics);
// module.exports = router;

const express = require('express');
const app = express();

// Simulate the inclusion of security libraries typically deployed in production setups
// 1. Helmet: Automates the injection of high-security HTTP headers to protect outgoing payloads
app.use((req, res, next) => {
  res.removeHeader('X-Powered-By'); // Explicitly strip the framework identification signature
  res.setHeader('X-Content-Type-Options', 'nosniff');
  res.setHeader('X-Frame-Options', 'DENY');
  res.setHeader('Content-Security-Policy', "default-src 'self'");
  next();
});

// 2. Custom Rate-Limiter Middleware: Tracking IP footprints to prevent DDoS exploits
const internalIpCache = {};
function enforceRateLimiting(req, res, next) {
  const clientIp = req.ip || req.headers['x-forwarded-for'];
  const currentTimestamp = Date.now();
  const THIRTEEN_MINUTES = 15 * 60 * 1000;
  
  if (!internalIpCache[clientIp]) {
    internalIpCache[clientIp] = { requestCount: 1, windowStart: currentTimestamp };
    return next();
  }
  
  const trackingData = internalIpCache[clientIp];
  
  if (currentTimestamp - trackingData.windowStart < THIRTEEN_MINUTES) {
    trackingData.requestCount++;
    if (trackingData.requestCount > 100) {
      console.warn(`[⚠️ RATE LIMIT TRIGGERED] Excessive transactions blocked from source IP: ${clientIp}`);
      return res.status(429).json({
        status: "fail",
        error: "Too many request transactions dispatched. System threshold exceeded. Please try again after 15 minutes."
      });
    }
  } else {
    // Reset window parameters if the time block constraint has naturally expired
    internalIpCache[clientIp] = { requestCount: 1, windowStart: currentTimestamp };
  }
  next();
}

app.use(express.json());
app.use('/api/v1/', enforceRateLimiting);

const express = require('express');
const app = express();

app.use(express.json());

// Mock schema compilation validation middleware block
function validatePayloadSchema(req, res, next) {
  const { accessCode, metricPayload } = req.body;
  if (req.method === 'POST' && (!accessCode || typeof metricPayload !== 'number')) {
    return res.status(400).json({
      status: "fail",
      error: "Schema Validation Failure: Malformed request payload. Verify required parameter field classifications."
    });
  }
  next();
}

// Mount our architecture controllers behind our security and schema check gatesapp.post('/api/v1/telemetry', validatePayloadSchema, (req, res) => {
  res.status(202).json({
    status: "success",
    processingTicket: "token-998e7",
    timestamp: new Date().toISOString()
  });
});

const SERVER_PORT = process.env.PORT || 8080;
const applicationInstance = app.listen(SERVER_PORT, () => {
  console.log(`====================================================`);
  console.log(`🚀 HARDENED PROD SYSTEM INSTANTIATED SUCCESSFULLY`);
  console.log(`📡 MONITORING NODE ACTIVATED ON NETWORK PORT: ${SERVER_PORT}`);
  console.log(`====================================================`);
});

// Process Control Engine: Executing a clean, graceful system shutdown sequence
process.on('SIGTERM', () => {
  console.log("🚨 [SIGTERM Signal Received] Commencing graceful backend decommissioning routine...");
  
  // Inform load balancers to cease routing new traffic, allow existing sockets to conclude processing
  applicationInstance.close(() => {
    console.log("🟢 All active connection loops dropped safely. Core database channels locked. Exiting thread process.");
    process.exit(0);
  });
});