Optimize for high concurrency: Node.js clustering, Web Workers, and system tuning

proxy-server.js

@@ -7,8 +7,10 @@
 const http = require('http');
 const https = require('https');
 const url = require('url');
+const cluster = require('cluster');
+const numCPUs = require('os').cpus().length;
 
-const PORT = 3000;
+const PORT = process.env.PORT || 3000;
 
 // Configuration
 const CONFIG = {
@@ -20,7 +22,7 @@ const CONFIG = {
     allowedOrigins: '*',
 
     // Maximum concurrent connections
-    maxConnections: 5000,
+    maxConnections: 10000, // Increased for cluster
 
     // User agents for rotation
     userAgents: [
@@ -32,6 +34,10 @@ const CONFIG = {
     ]
 };
 
+// Global agents for connection pooling
+const httpAgent = new http.Agent({ keepAlive: true, maxSockets: Infinity });
+const httpsAgent = new https.Agent({ keepAlive: true, maxSockets: Infinity });
+
 // Get random user agent
 function getRandomUserAgent() {
     return CONFIG.userAgents[Math.floor(Math.random() * CONFIG.userAgents.length)];
@@ -44,7 +50,6 @@ const getGitInfo = () => {
     return new Promise((resolve) => {
         exec('git rev-parse --short HEAD && git log -1 --format=%cd --date=relative', (err, stdout) => {
             if (err) {
-                console.error('Error fetching git info:', err);
                 resolve({ commit: 'Unknown', date: 'Unknown' });
                 return;
             }
@@ -57,8 +62,31 @@ const getGitInfo = () => {
     });
 };
 
-// Create the proxy server
-const server = http.createServer((req, res) => {
+if (cluster.isMaster) {
+    console.log(`Master ${process.pid} is running`);
+    console.log(`Spawning ${numCPUs} workers...`);
+
+    for (let i = 0; i < numCPUs; i++) {
+        cluster.fork();
+    }
+
+    cluster.on('exit', (worker, code, signal) => {
+        console.log(`Worker ${worker.process.pid} died. Respawning...`);
+        cluster.fork();
+    });
+
+    // Master process only listens for SIGINT to gracefully shut down workers
+    process.on('SIGINT', () => {
+        console.log('\n\n🛑 Shutting down proxy server (master)...');
+        for (const id in cluster.workers) {
+            cluster.workers[id].kill();
+        }
+        process.exit(0);
+    });
+
+} else {
+    // Create the proxy server
+    const server = http.createServer((req, res) => {
         // Handle CORS preflight requests
         if (req.method === 'OPTIONS') {
             handleCORS(res);
@@ -67,6 +95,14 @@ const server = http.createServer((req, res) => {
             return;
         }
 
+        // Health check
+        if (req.url === '/health' || req.url === '//health') {
+            handleCORS(res);
+            res.writeHead(200, { 'Content-Type': 'application/json' });
+            res.end(JSON.stringify({ status: 'ok', worker: process.pid }));
+            return;
+        }
+
         // Handle Git Info request
         // Nginx proxy_pass might result in double slashes (//git-info)
         if ((req.url === '/git-info' || req.url === '//git-info') && req.method === 'GET') {
@@ -103,10 +139,10 @@ const server = http.createServer((req, res) => {
                 }));
             }
         });
-});
+    });
 
-// Handle the actual proxy request
-function handleProxyRequest(proxyRequest, clientRes) {
+    // Handle the actual proxy request
+    function handleProxyRequest(proxyRequest, clientRes) {
         const { targetUrl, method = 'GET', headers = {}, body = null } = proxyRequest;
 
         // Validate target URL
@@ -125,8 +161,10 @@ function handleProxyRequest(proxyRequest, clientRes) {
             return;
         }
 
-    // Determine if we need http or https
-    const protocol = parsedUrl.protocol === 'https:' ? https : http;
+        // Determine if we need http or https and which agent to use
+        const isHttps = parsedUrl.protocol === 'https:';
+        const protocol = isHttps ? https : http;
+        const agent = isHttps ? httpsAgent : httpAgent;
 
         // Prepare request options with random user agent
         const options = {
@@ -134,6 +172,7 @@ function handleProxyRequest(proxyRequest, clientRes) {
             port: parsedUrl.port,
             path: parsedUrl.pathname + parsedUrl.search,
             method: method,
+            agent: agent, // Use the global agent for connection pooling
             headers: {
                 ...headers,
                 'User-Agent': getRandomUserAgent(),
@@ -178,7 +217,8 @@ function handleProxyRequest(proxyRequest, clientRes) {
                     responseTime: responseTime,
                     headers: proxyRes.headers,
                     body: responseData, // Full body for crawler link extraction
-                bodySize: responseSize
+                    bodySize: responseSize,
+                    proxyWorker: process.pid // Add worker ID for debugging
                 }));
             });
         });
@@ -220,54 +260,32 @@ function handleProxyRequest(proxyRequest, clientRes) {
         }
 
         proxyReq.end();
-}
+    }
 
-// Add CORS headers to response
-function handleCORS(res) {
+    // Add CORS headers to response
+    function handleCORS(res) {
         res.setHeader('Access-Control-Allow-Origin', CONFIG.allowedOrigins);
         res.setHeader('Access-Control-Allow-Methods', 'POST, GET, OPTIONS');
         res.setHeader('Access-Control-Allow-Headers', 'Content-Type');
-}
-
-// Start the server
-server.listen(PORT, () => {
-    console.log(`
-╔════════════════════════════════════════════════════════════╗
-║         CORS Proxy Server for Stress Testing Tool         ║
-╚════════════════════════════════════════════════════════════╝
-
-✅ Server running on: http://localhost:${PORT}
-✅ Max connections: ${CONFIG.maxConnections}
-✅ Request timeout: ${CONFIG.timeout}ms
-
-📝 Usage:
-   POST to http://localhost:${PORT} with JSON body:
-   {
-     "targetUrl": "https://example.com",
-     "method": "GET",
-     "headers": {},
-     "body": null
     }
 
-🔒 Security Note:
-   For production, update CONFIG.allowedOrigins to your
-   stress testing tool's domain (not '*')
+    // Start the server
+    server.listen(PORT, () => {
+        console.log(`Worker ${process.pid} running on http://localhost:${PORT}`);
+    });
 
-Press Ctrl+C to stop the server
-  `);
-});
-
-// Handle server errors
-server.on('error', (error) => {
-    console.error('❌ Server error:', error.message);
+    // Handle server errors
+    server.on('error', (error) => {
+        console.error(`❌ Worker ${process.pid} server error:`, error.message);
         process.exit(1);
-});
+    });
 
-// Graceful shutdown
-process.on('SIGINT', () => {
-    console.log('\n\n🛑 Shutting down proxy server...');
+    // Graceful shutdown for workers
+    process.on('SIGINT', () => {
+        console.log(`\n\n🛑 Worker ${process.pid} shutting down...`);
         server.close(() => {
-        console.log('✅ Server closed');
+            console.log(`✅ Worker ${process.pid} closed`);
             process.exit(0);
         });
-});
+    });
+}

script.js

@@ -1,84 +1,3 @@
-// ===================================
-// STRESS TESTING TOOL - MAIN SCRIPT
-// Enhanced with Crawler & Advanced Features
-// ===================================
-
-// ===================================
-// WEBSITE CRAWLER CLASS
-// ===================================
-class WebsiteCrawler {
-  constructor() {
-    this.visitedUrls = new Set();
-    this.urlQueue = [];
-  }
-
-  extractLinks(html, baseUrl) {
-    const links = [];
-    const parser = new DOMParser();
-    const doc = parser.parseFromString(html, "text/html");
-    const anchorTags = doc.querySelectorAll("a[href]");
-
-    const baseUrlObj = new URL(baseUrl);
-
-    anchorTags.forEach((anchor) => {
-      try {
-        const href = anchor.getAttribute("href");
-        if (
-          !href ||
-          href.startsWith("#") ||
-          href.startsWith("javascript:") ||
-          href.startsWith("mailto:")
-        ) {
-          return;
-        }
-
-        const absoluteUrl = new URL(href, baseUrl);
-
-        // Only include links from the same domain if configured
-        if (absoluteUrl.hostname === baseUrlObj.hostname) {
-          const urlString = absoluteUrl.href;
-          if (!this.visitedUrls.has(urlString)) {
-            links.push(urlString);
-          }
-        }
-      } catch (e) {
-        // Invalid URL, skip
-      }
-    });
-
-    return links;
-  }
-
-  getNextUrl(currentUrl, html, config) {
-    // Extract links from current page
-    const links = this.extractLinks(html, currentUrl);
-
-    // Add new links to queue (limit per page)
-    const linksToAdd = links.slice(0, config.linksPerPage || 10);
-    linksToAdd.forEach((link) => {
-      if (!this.visitedUrls.has(link) && this.urlQueue.length < 100) {
-        this.urlQueue.push(link);
-      }
-    });
-
-    // Mark current URL as visited
-    this.visitedUrls.add(currentUrl);
-
-    // Get next URL from queue
-    if (this.urlQueue.length > 0) {
-      const randomIndex = Math.floor(Math.random() * this.urlQueue.length);
-      return this.urlQueue.splice(randomIndex, 1)[0];
-    }
-
-    return null;
-  }
-
-  reset() {
-    this.visitedUrls.clear();
-    this.urlQueue = [];
-  }
-}
-
 // ===================================
 // UTILITY FUNCTIONS
 // ===================================
@@ -143,11 +62,13 @@ class StressTestingTool {
       failedRequests: 0,
       responseTimes: [],
       requestsPerSecond: [],
-      workers: [],
+      workers: [], // Web Worker instances
+      workerStats: new Map(), // Stats per worker
       updateInterval: null,
       chartUpdateInterval: null,
       userErrorData: [],
       errorThreshold: null,
+      lastUiUpdate: 0,
 
       // Enhanced metrics
       errorsByCategory: {
@@ -168,7 +89,6 @@ class StressTestingTool {
       },
     };
 
-    this.crawler = new WebsiteCrawler();
     this.charts = {
       rps: null,
       responseTime: null,
@@ -880,223 +800,85 @@ class StressTestingTool {
   }
 
   startWorkers() {
-    const pattern = this.config.trafficPattern;
+    const totalUsers = this.config.userCount;
+    const workerCount = Math.min(Math.ceil(totalUsers / 100), navigator.hardwareConcurrency || 4);
+    const usersPerWorker = Math.ceil(totalUsers / workerCount);
 
-    switch (pattern) {
-      case "steady":
-        this.startSteadyLoad();
-        break;
-      case "burst":
-        this.startBurstLoad();
-        break;
-      case "rampup":
-        this.startRampUpLoad();
-        break;
-      case "random":
-        this.startRandomLoad();
-        break;
-    }
-  }
+    for (let i = 0; i < workerCount; i++) {
+      const worker = new Worker('worker.js');
+      const startUser = i * usersPerWorker;
+      const endUser = Math.min((i + 1) * usersPerWorker, totalUsers);
+      const workerUsers = Array.from({ length: endUser - startUser }, (_, j) => startUser + j);
 
-  startSteadyLoad() {
-    const delayBetweenUsers = 100;
+      worker.onmessage = (e) => this.handleWorkerMessage(i, e.data);
 
-    for (let i = 0; i < this.config.userCount; i++) {
-      setTimeout(() => {
-        if (this.state.status === "running") {
-          this.createWorker(i);
-        }
-      }, i * delayBetweenUsers);
-    }
-  }
+      worker.postMessage({
+        type: 'INIT',
+        data: { config: this.config }
+      });
 
-  startBurstLoad() {
-    const burstSize = Math.ceil(this.config.userCount / 5);
-    const burstInterval = (this.config.duration * 1000) / 5;
-
-    for (let burst = 0; burst < 5; burst++) {
-      setTimeout(() => {
-        if (this.state.status === "running") {
-          for (let i = 0; i < burstSize; i++) {
-            this.createWorker(burst * burstSize + i);
-          }
-        }
-      }, burst * burstInterval);
-    }
-  }
-
-  startRampUpLoad() {
-    const totalTime = this.config.duration * 1000;
-    const timePerUser = totalTime / this.config.userCount;
-
-    for (let i = 0; i < this.config.userCount; i++) {
-      setTimeout(() => {
-        if (this.state.status === "running") {
-          this.createWorker(i);
-        }
-      }, i * timePerUser);
-    }
-  }
-
-  startRandomLoad() {
-    const maxDelay = (this.config.duration * 1000) / 2;
-
-    for (let i = 0; i < this.config.userCount; i++) {
-      const randomDelay = Math.random() * maxDelay;
-      setTimeout(() => {
-        if (this.state.status === "running") {
-          this.createWorker(i);
-        }
-      }, randomDelay);
-    }
-  }
-
-  createWorker(id) {
-    const worker = {
-      id: id,
-      active: true,
-      requestCount: 0,
-      currentUrl: this.config.targetUrl,
-      crawlDepth: 0,
-    };
+      worker.postMessage({
+        type: 'START',
+        data: { users: workerUsers }
+      });
 
       this.state.workers.push(worker);
-    this.state.activeUsers++;
-    this.runWorker(worker);
-  }
-
-  async runWorker(worker) {
-    const endTime = this.state.startTime + this.config.duration * 1000;
-
-    while (
-      worker.active &&
-      this.state.status === "running" &&
-      Date.now() < endTime
-    ) {
-      await this.makeRequest(worker);
-
-      // Think time
-      if (this.config.thinkTime > 0) {
-        await this.sleep(this.config.thinkTime);
-      }
-    }
-
-    // Worker finished
-    worker.active = false;
-    this.state.activeUsers--;
-
-    // Check if all workers are done
-    if (this.state.activeUsers === 0 && this.state.status === "running") {
-      this.stopTest();
-    }
-  }
-
-  async makeRequest(worker) {
-    const startTime = performance.now();
-    const requestUrl = worker.currentUrl;
-
-    try {
-      const proxyPayload = {
-        targetUrl: requestUrl,
-        method: this.config.httpMethod,
-        headers: this.config.customHeaders,
-        body: this.config.requestBody,
-      };
-
-      // Estimate request size
-      const requestSize = JSON.stringify(proxyPayload).length;
-      this.state.totalBytesSent += requestSize;
-
-      const response = await fetch(this.config.proxyUrl, {
-        method: "POST",
-        headers: {
-          "Content-Type": "application/json",
-        },
-        body: JSON.stringify(proxyPayload),
-      });
-
-      const endTime = performance.now();
-      const responseTime = endTime - startTime;
-
-      this.state.totalRequests++;
-      worker.requestCount++;
-
-      const proxyResponse = await response.json();
-
-      // Track response size
-      if (proxyResponse.body) {
-        this.state.totalBytesReceived += proxyResponse.body.length;
-      }
-
-      const isSuccess =
-        proxyResponse.success &&
-        proxyResponse.statusCode >= 200 &&
-        proxyResponse.statusCode < 400;
-
-      if (isSuccess) {
-        this.state.successfulRequests++;
-      } else {
-        this.state.failedRequests++;
-        const category = categorizeError(
-          proxyResponse.statusCode,
-          proxyResponse.error
-        );
-        this.state.errorsByCategory[category]++;
-      }
-
-      const actualResponseTime = proxyResponse.responseTime || responseTime;
-      this.state.responseTimes.push(actualResponseTime);
-
-      // Keep only last 1000 response times
-      if (this.state.responseTimes.length > 1000) {
-        this.state.responseTimes.shift();
-      }
-
-      // Add to request history
-      this.addToRequestHistory({
-        url: requestUrl,
-        status: proxyResponse.statusCode,
-        responseTime: Math.round(actualResponseTime),
-        success: isSuccess,
-        timestamp: new Date().toLocaleTimeString(),
-      });
-
-      // Crawler: Get next URL if enabled
-      if (
-        this.config.crawlerEnabled &&
-        isSuccess &&
-        proxyResponse.body &&
-        worker.crawlDepth < this.config.crawlDepth
-      ) {
-        const nextUrl = this.crawler.getNextUrl(
-          requestUrl,
-          proxyResponse.body,
-          this.config
-        );
-        if (nextUrl) {
-          worker.currentUrl = nextUrl;
-          worker.crawlDepth++;
-        }
-      }
-    } catch (error) {
-      const endTime = performance.now();
-      const responseTime = endTime - startTime;
-
-      this.state.totalRequests++;
-      this.state.failedRequests++;
-      this.state.responseTimes.push(responseTime);
-      this.state.errorsByCategory["network"]++;
-      worker.requestCount++;
-
-      this.addToRequestHistory({
-        url: requestUrl,
-        status: 0,
-        responseTime: Math.round(responseTime),
-        success: false,
-        timestamp: new Date().toLocaleTimeString(),
-        error: error.message,
+      this.state.workerStats.set(i, {
+        totalRequests: 0,
+        successfulRequests: 0,
+        failedRequests: 0,
+        bytesSent: 0,
+        bytesReceived: 0,
+        errorsByCategory: { "4xx": 0, "5xx": 0, "timeout": 0, "network": 0 },
+        responseTimes: []
       });
     }
+
+    this.state.activeUsers = totalUsers;
+  }
+
+  handleWorkerMessage(workerId, message) {
+    if (message.type === 'STATS') {
+      this.state.workerStats.set(workerId, message.data);
+      this.aggregateStats();
+    } else if (message.type === 'LOG') {
+      this.addToRequestHistory(message.data);
+    }
+  }
+
+  aggregateStats() {
+    let totalRequests = 0;
+    let successfulRequests = 0;
+    let failedRequests = 0;
+    let bytesSent = 0;
+    let bytesReceived = 0;
+    let errors = { "4xx": 0, "5xx": 0, "timeout": 0, "network": 0 };
+    let allResponseTimes = [];
+
+    for (const stats of this.state.workerStats.values()) {
+      totalRequests += stats.totalRequests;
+      successfulRequests += stats.successfulRequests;
+      failedRequests += stats.failedRequests;
+      bytesSent += stats.bytesSent;
+      bytesReceived += stats.bytesReceived;
+
+      errors["4xx"] += stats.errorsByCategory["4xx"];
+      errors["5xx"] += stats.errorsByCategory["5xx"];
+      errors["timeout"] += stats.errorsByCategory["timeout"];
+      errors["network"] += stats.errorsByCategory["network"];
+
+      if (stats.responseTimes) {
+        allResponseTimes = allResponseTimes.concat(stats.responseTimes);
+      }
+    }
+
+    this.state.totalRequests = totalRequests;
+    this.state.successfulRequests = successfulRequests;
+    this.state.failedRequests = failedRequests;
+    this.state.totalBytesSent = bytesSent;
+    this.state.totalBytesReceived = bytesReceived;
+    this.state.errorsByCategory = errors;
+    this.state.responseTimes = allResponseTimes.slice(-1000); // Sample for percentiles
   }
 
   addToRequestHistory(request) {
@@ -1113,25 +895,16 @@ class StressTestingTool {
       row.className = request.success ? "success-row" : "error-row";
       row.innerHTML = `
         <td>${request.timestamp}</td>
-        <td class="url-cell" title="${request.url}">${this.truncateUrl(
-        request.url
-      )}</td>
-        <td><span class="status-code ${
-          request.success ? "success" : "error"
-        }">${request.status}</span></td>
+        <td class="url-cell" title="${request.url}">${this.truncateUrl(request.url)}</td>
+        <td><span class="status-code ${request.success ? "success" : "error"}">${request.status}</span></td>
         <td>${request.responseTime}ms</td>
       `;
 
-      this.elements.requestHistoryBody.insertBefore(
-        row,
-        this.elements.requestHistoryBody.firstChild
-      );
+      this.elements.requestHistoryBody.insertBefore(row, this.elements.requestHistoryBody.firstChild);
 
       // Keep only 100 rows in DOM
       while (this.elements.requestHistoryBody.children.length > 100) {
-        this.elements.requestHistoryBody.removeChild(
-          this.elements.requestHistoryBody.lastChild
-        );
+        this.elements.requestHistoryBody.removeChild(this.elements.requestHistoryBody.lastChild);
       }
     }
   }
@@ -1145,8 +918,10 @@ class StressTestingTool {
 
   stopWorkers() {
     this.state.workers.forEach((worker) => {
-      worker.active = false;
+      worker.terminate();
     });
+    this.state.workers = [];
+    this.state.workerStats.clear();
   }
 
   calculatePercentiles() {
@@ -1165,6 +940,13 @@ class StressTestingTool {
 
   updateStatistics() {
     const now = Date.now();
+
+    // Check if enough time has passed for a UI update (1000ms throttled)
+    if (this.state.status === "running" && now - this.state.lastUiUpdate < 1000) {
+      return;
+    }
+    this.state.lastUiUpdate = now;
+
     const elapsed = Math.floor((now - this.state.startTime) / 1000);
     const remaining = Math.max(0, this.config.duration - elapsed);
     const progress = Math.min(100, (elapsed / this.config.duration) * 100);

setup-server.sh

@@ -1,23 +1,25 @@
-#!/bin/bash
-
 # setup-server.sh - Initial Setup Script
 
-# 1. Install Global Dependencies
+# 1. System Tuning for High Concurrency
+echo "Tuning system limits..."
+# Increase max open files for high connection counts
+if ! grep -q "soft nofile 65535" /etc/security/limits.conf; then
+    echo "* soft nofile 65535" >> /etc/security/limits.conf
+    echo "* hard nofile 65535" >> /etc/security/limits.conf
+fi
+# Apply limits to current session (for the rest of this script)
+ulimit -n 65535
+
+# 2. Install Global Dependencies
 echo "Installing PM2..."
 npm install -g pm2
 
-# 2. Clone Repository
-# Expects: REPO_URL, APP_DIR, GITHUB_TOKEN inside the script or env
-# We'll use arguments passed to this script: $1=REPO_URL $2=APP_DIR $3=GITHUB_TOKEN
-
+# 3. Clone Repository
+# ... (rest of cloning logic)
 REPO_URL="$1"
 APP_DIR="$2"
 GITHUB_TOKEN="$3"
 
-# Construct URL with token for auth
-# Extract host and path from REPO_URL (assuming https://github.com/user/repo.git)
-# We need to insert token: https://TOKEN@github.com/user/repo.git
-# Simple replacement:
 AUTH_REPO_URL="${REPO_URL/https:\/\//https:\/\/$GITHUB_TOKEN@}"
 
 echo "Preparing application directory: $APP_DIR"
@@ -33,18 +35,20 @@ else
     cd "$APP_DIR"
 fi
 
-# 3. Install App Dependencies
+# 4. Install App Dependencies
 echo "Installing application dependencies..."
 npm install
 
-# 4. Start Application with PM2
+# 5. Start Application with PM2
 APP_NAME="website-stress-test"
 echo "Starting application with PM2 ($APP_NAME)..."
-pm2 start proxy-server.js --name "$APP_NAME" --watch --ignore-watch="node_modules"
+# Using Node built-in clustering, but PM2 monitors the master
+pm2 stop "$APP_NAME" || true
+pm2 start proxy-server.js --name "$APP_NAME" --max-memory-restart 1G
 pm2 save
 pm2 startup | tail -n 1 | bash # Setup startup script
 
-# 5. Setup Cron Job for Auto-Sync
+# 6. Setup Cron Job for Auto-Sync
 echo "Setting up Cron Job for auto-sync..."
 SCRIPT_PATH="$APP_DIR/auto-sync.sh"
 chmod +x "$SCRIPT_PATH"
@@ -52,5 +56,5 @@ chmod +x "$SCRIPT_PATH"
 # Add to crontab if not exists
 (crontab -l 2>/dev/null; echo "*/5 * * * * $SCRIPT_PATH >> /var/log/app-sync.log 2>&1") | crontab -
 
-echo "✅ Setup Complete! Application is running."
+echo "✅ Setup Complete! Application is running with system optimizations."
 pm2 status

worker.js

@@ -0,0 +1,237 @@
+// ===================================
+// STRESS TESTING TOOL - WEB WORKER
+// Handles request loops for a group of users
+// ===================================
+
+let config = {};
+let state = {
+    active: false,
+    users: [],
+    startTime: 0,
+    totalRequests: 0,
+    successfulRequests: 0,
+    failedRequests: 0,
+    responseTimes: [],
+    bytesSent: 0,
+    bytesReceived: 0,
+    errorsByCategory: {
+        "4xx": 0,
+        "5xx": 0,
+        "timeout": 0,
+        "network": 0
+    }
+};
+
+// Listen for messages from the main thread
+self.onmessage = function (e) {
+    const { type, data } = e.data;
+
+    switch (type) {
+        case 'INIT':
+            config = data.config;
+            break;
+        case 'START':
+            state.active = true;
+            state.startTime = Date.now();
+            startUsers(data.users);
+            break;
+        case 'STOP':
+            state.active = false;
+            break;
+    }
+};
+
+async function startUsers(userIndices) {
+    const pattern = config.trafficPattern;
+    const totalDuration = config.duration * 1000;
+
+    for (const index of userIndices) {
+        if (!state.active) break;
+
+        const delay = calculateStartDelay(index, userIndices.length, pattern, totalDuration);
+
+        setTimeout(() => {
+            if (state.active) {
+                runUser(index);
+            }
+        }, delay);
+    }
+
+    // Start reporting results periodically
+    const reportInterval = setInterval(() => {
+        if (!state.active) {
+            clearInterval(reportInterval);
+            return;
+        }
+        reportResults();
+    }, 500);
+}
+
+function calculateStartDelay(index, count, pattern, duration) {
+    switch (pattern) {
+        case 'steady':
+            return (index % count) * 100;
+        case 'burst':
+            const burstIndex = Math.floor((index % count) / (count / 5));
+            return burstIndex * (duration / 5);
+        case 'rampup':
+            return (index % count) * (duration / count);
+        case 'random':
+            return Math.random() * (duration / 2);
+        default:
+            return 0;
+    }
+}
+
+async function runUser(id) {
+    const endTime = state.startTime + config.duration * 1000;
+    let currentUrl = config.targetUrl;
+    let crawlDepth = 0;
+
+    while (state.active && Date.now() < endTime) {
+        const result = await makeRequest(currentUrl);
+
+        // Report individual request for history log (sampled)
+        if (Math.random() < 0.1 || config.userCount < 50) {
+            self.postMessage({
+                type: 'LOG',
+                data: {
+                    url: currentUrl,
+                    status: result.status,
+                    responseTime: result.responseTime,
+                    success: result.success,
+                    timestamp: new Date().toLocaleTimeString()
+                }
+            });
+        }
+
+        // Logic for crawler (simplified for worker)
+        if (config.crawlerEnabled && result.success && result.body && crawlDepth < config.crawlDepth) {
+            const nextUrl = extractRandomLink(result.body, currentUrl);
+            if (nextUrl) {
+                currentUrl = nextUrl;
+                crawlDepth++;
+            }
+        }
+
+        // Think time with jitter
+        const jitter = 0.5 + Math.random(); // 50% to 150%
+        const sleepTime = config.thinkTime * jitter;
+        await new Promise(resolve => setTimeout(resolve, sleepTime));
+    }
+}
+
+async function makeRequest(targetUrl) {
+    const startTime = performance.now();
+    let result = {
+        success: false,
+        status: 0,
+        responseTime: 0,
+        body: null
+    };
+
+    try {
+        const payload = {
+            targetUrl: targetUrl,
+            method: config.httpMethod,
+            headers: config.customHeaders,
+            body: config.requestBody
+        };
+
+        const payloadStr = JSON.stringify(payload);
+        state.bytesSent += payloadStr.length;
+
+        const response = await fetch(config.proxyUrl, {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: payloadStr
+        });
+
+        const proxyResponse = await response.json();
+        const endTime = performance.now();
+
+        result.responseTime = proxyResponse.responseTime || (endTime - startTime);
+        result.status = proxyResponse.statusCode;
+        result.success = proxyResponse.success && result.status >= 200 && result.status < 400;
+        result.body = proxyResponse.body;
+
+        if (result.body) {
+            state.bytesReceived += result.body.length;
+        }
+
+        updateStats(result);
+
+    } catch (error) {
+        result.responseTime = performance.now() - startTime;
+        state.failedRequests++;
+        state.errorsByCategory["network"]++;
+    }
+
+    return result;
+}
+
+function updateStats(result) {
+    state.totalRequests++;
+    if (result.success) {
+        state.successfulRequests++;
+    } else {
+        state.failedRequests++;
+        const category = categorizeError(result.status);
+        state.errorsByCategory[category]++;
+    }
+    state.responseTimes.push(result.responseTime);
+
+    // Keep response times capped in worker to save memory
+    if (state.responseTimes.length > 500) {
+        state.responseTimes.shift();
+    }
+}
+
+function categorizeError(status) {
+    if (status >= 400 && status < 500) return "4xx";
+    if (status >= 500) return "5xx";
+    return "network";
+}
+
+function reportResults() {
+    self.postMessage({
+        type: 'STATS',
+        data: {
+            totalRequests: state.totalRequests,
+            successfulRequests: state.successfulRequests,
+            failedRequests: state.failedRequests,
+            bytesSent: state.bytesSent,
+            bytesReceived: state.bytesReceived,
+            errorsByCategory: state.errorsByCategory,
+            responseTimes: state.responseTimes // Sampled
+        }
+    });
+
+    // Clear local counters that are cumulative but reported incrementally if needed
+    // Actually, state object above is cumulative. Main thread will track totals.
+}
+
+function extractRandomLink(html, baseUrl) {
+    try {
+        const linkRegex = /href=["'](https?:\/\/[^"']+|(?:\/[^"']+))["']/gi;
+        const links = [];
+        let match;
+        const baseUrlObj = new URL(baseUrl);
+
+        while ((match = linkRegex.exec(html)) !== null) {
+            let href = match[1];
+            try {
+                const absoluteUrl = new URL(href, baseUrl);
+                if (absoluteUrl.hostname === baseUrlObj.hostname) {
+                    links.push(absoluteUrl.href);
+                }
+            } catch (e) { }
+            if (links.length > 50) break; // Limit extraction
+        }
+
+        if (links.length > 0) {
+            return links[Math.floor(Math.random() * links.length)];
+        }
+    } catch (e) { }
+    return null;
+}