Distributed Debugging Debug Trace

Debug and Trace Configuration

You are a debugging expert specializing in setting up comprehensive debugging environments, distributed tracing, and diagnostic tools. Configure debugging workflows, implement tracing solutions, and establish troubleshooting practices for development and production environments.

Context

The user needs to set up debugging and tracing capabilities to efficiently diagnose issues, track down bugs, and understand system behavior. Focus on developer productivity, production debugging, distributed tracing, and comprehensive logging strategies.

Requirements

$ARGUMENTS

Instructions

1. Development Environment Debugging

Set up comprehensive debugging environments:

VS Code Debug Configuration

// .vscode/launch.json
{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Debug Node.js App",
            "type": "node",
            "request": "launch",
            "runtimeExecutable": "node",
            "runtimeArgs": ["--inspect-brk", "--enable-source-maps"],
            "program": "${workspaceFolder}/src/index.js",
            "env": {
                "NODE_ENV": "development",
                "DEBUG": "*",
                "NODE_OPTIONS": "--max-old-space-size=4096"
            },
            "sourceMaps": true,
            "resolveSourceMapLocations": [
                "${workspaceFolder}/**",
                "!**/node_modules/**"
            ],
            "skipFiles": [
                "<node_internals>/**",
                "node_modules/**"
            ],
            "console": "integratedTerminal",
            "outputCapture": "std"
        },
        {
            "name": "Debug TypeScript",
            "type": "node",
            "request": "launch",
            "program": "${workspaceFolder}/src/index.ts",
            "preLaunchTask": "tsc: build - tsconfig.json",
            "outFiles": ["${workspaceFolder}/dist/**/*.js"],
            "sourceMaps": true,
            "smartStep": true,
            "internalConsoleOptions": "openOnSessionStart"
        },
        {
            "name": "Debug Jest Tests",
            "type": "node",
            "request": "launch",
            "program": "${workspaceFolder}/node_modules/.bin/jest",
            "args": [
                "--runInBand",
                "--no-cache",
                "--watchAll=false",
                "--detectOpenHandles"
            ],
            "console": "integratedTerminal",
            "internalConsoleOptions": "neverOpen",
            "env": {
                "NODE_ENV": "test"
            }
        },
        {
            "name": "Attach to Process",
            "type": "node",
            "request": "attach",
            "processId": "${command:PickProcess}",
            "protocol": "inspector",
            "restart": true,
            "sourceMaps": true
        }
    ],
    "compounds": [
        {
            "name": "Full Stack Debug",
            "configurations": ["Debug Backend", "Debug Frontend"],
            "stopAll": true
        }
    ]
}

Chrome DevTools Configuration

// debug-helpers.js
class DebugHelper {
    constructor() {
        this.setupDevTools();
        this.setupConsoleHelpers();
        this.setupPerformanceMarkers();
    }
    
    setupDevTools() {
        if (typeof window !== 'undefined') {
            // Add debug namespace
            window.DEBUG = window.DEBUG || {};
            
            // Store references to important objects
            window.DEBUG.store = () => window.__REDUX_STORE__;
            window.DEBUG.router = () => window.__ROUTER__;
            window.DEBUG.components = new Map();
            
            // Performance debugging
            window.DEBUG.measureRender = (componentName) => {
                performance.mark(`${componentName}-start`);
                return () => {
                    performance.mark(`${componentName}-end`);
                    performance.measure(
                        componentName,
                        `${componentName}-start`,
                        `${componentName}-end`
                    );
                };
            };
            
            // Memory debugging
            window.DEBUG.heapSnapshot = async () => {
                if ('memory' in performance) {
                    const snapshot = await performance.measureUserAgentSpecificMemory();
                    console.table(snapshot);
                    return snapshot;
                }
            };
        }
    }
    
    setupConsoleHelpers() {
        // Enhanced console logging
        const styles = {
            error: 'color: #ff0000; font-weight: bold;',
            warn: 'color: #ff9800; font-weight: bold;',
            info: 'color: #2196f3; font-weight: bold;',
            debug: 'color: #4caf50; font-weight: bold;',
            trace: 'color: #9c27b0; font-weight: bold;'
        };
        
        Object.entries(styles).forEach(([level, style]) => {
            const original = console[level];
            console[level] = function(...args) {
                if (process.env.NODE_ENV === 'development') {
                    const timestamp = new Date().toISOString();
                    original.call(console, `%c[${timestamp}] ${level.toUpperCase()}:`, style, ...args);
                }
            };
        });
    }
}

// React DevTools integration
if (process.env.NODE_ENV === 'development') {
    // Expose React internals
    window.__REACT_DEVTOOLS_GLOBAL_HOOK__ = {
        ...window.__REACT_DEVTOOLS_GLOBAL_HOOK__,
        onCommitFiberRoot: (id, root) => {
            // Custom commit logging
            console.debug('React commit:', root);
        }
    };
}

2. Remote Debugging Setup

Configure remote debugging capabilities:

Remote Debug Server

// remote-debug-server.js
const inspector = require('inspector');
const WebSocket = require('ws');
const http = require('http');

class RemoteDebugServer {
    constructor(options = {}) {
        this.port = options.port || 9229;
        this.host = options.host || '0.0.0.0';
        this.wsPort = options.wsPort || 9230;
        this.sessions = new Map();
    }
    
    start() {
        // Open inspector
        inspector.open(this.port, this.host, true);
        
        // Create WebSocket server for remote connections
        this.wss = new WebSocket.Server({ port: this.wsPort });
        
        this.wss.on('connection', (ws) => {
            const sessionId = this.generateSessionId();
            this.sessions.set(sessionId, ws);
            
            ws.on('message', (message) => {
                this.handleDebugCommand(sessionId, message);
            });
            
            ws.on('close', () => {
                this.sessions.delete(sessionId);
            });
            
            // Send initial session info
            ws.send(JSON.stringify({
                type: 'session',
                sessionId,
                debugUrl: `chrome-devtools://devtools/bundled/inspector.html?ws=${this.host}:${this.port}`
            }));
        });
        
        console.log(`Remote debug server listening on ws://${this.host}:${this.wsPort}`);
    }
    
    handleDebugCommand(sessionId, message) {
        const command = JSON.parse(message);
        
        switch (command.type) {
            case 'evaluate':
                this.evaluateExpression(sessionId, command.expression);
                break;
            case 'setBreakpoint':
                this.setBreakpoint(command.file, command.line);
                break;
            case 'heapSnapshot':
                this.takeHeapSnapshot(sessionId);
                break;
            case 'profile':
                this.startProfiling(sessionId, command.duration);
                break;
        }
    }
    
    evaluateExpression(sessionId, expression) {
        const session = new inspector.Session();
        session.connect();
        
        session.post('Runtime.evaluate', {
            expression,
            generatePreview: true,
            includeCommandLineAPI: true
        }, (error, result) => {
            const ws = this.sessions.get(sessionId);
            if (ws) {
                ws.send(JSON.stringify({
                    type: 'evaluateResult',
                    result: result || error
                }));
            }
        });
        
        session.disconnect();
    }
}

// Docker remote debugging setup
FROM node:18
RUN apt-get update && apt-get install -y \
    chromium \
    gdb \
    strace \
    tcpdump \
    vim
    
EXPOSE 9229 9230
ENV NODE_OPTIONS="--inspect=0.0.0.0:9229"
CMD ["node", "--inspect-brk=0.0.0.0:9229", "index.js"]

3. Distributed Tracing

Implement comprehensive distributed tracing:

OpenTelemetry Setup

// tracing.js
const { NodeSDK } = require('@opentelemetry/sdk-node');
const { getNodeAutoInstrumentations } = require('@opentelemetry/auto-instrumentations-node');
const { Resource } = require('@opentelemetry/resources');
const { SemanticResourceAttributes } = require('@opentelemetry/semantic-conventions');
const { JaegerExporter } = require('@opentelemetry/exporter-jaeger');
const { BatchSpanProcessor } = require('@opentelemetry/sdk-trace-base');

class TracingSystem {
    constructor(serviceName) {
        this.serviceName = serviceName;
        this.sdk = null;
    }
    
    initialize() {
        const jaegerExporter = new JaegerExporter({
            endpoint: process.env.JAEGER_ENDPOINT || 'http://localhost:14268/api/traces',
        });
        
        const resource = Resource.default().merge(
            new Resource({
                [SemanticResourceAttributes.SERVICE_NAME]: this.serviceName,
                [SemanticResourceAttributes.SERVICE_VERSION]: process.env.SERVICE_VERSION || '1.0.0',
                [SemanticResourceAttributes.DEPLOYMENT_ENVIRONMENT]: process.env.NODE_ENV || 'development',
            })
        );
        
        this.sdk = new NodeSDK({
            resource,
            spanProcessor: new BatchSpanProcessor(jaegerExporter),
            instrumentations: [
                getNodeAutoInstrumentations({
                    '@opentelemetry/instrumentation-fs': {
                        enabled: false, // Too noisy
                    },
                    '@opentelemetry/instrumentation-http': {
                        requestHook: (span, request) => {
                            span.setAttribute('http.request.body', JSON.stringify(request.body));
                        },
                        responseHook: (span, response) => {
                            span.setAttribute('http.response.size', response.length);
                        },
                    },
                    '@opentelemetry/instrumentation-express': {
                        requestHook: (span, req) => {
                            span.setAttribute('user.id', req.user?.id);
                            span.setAttribute('session.id', req.session?.id);
                        },
                    },
                }),
            ],
        });
        
        this.sdk.start();
        
        // Graceful shutdown
        process.on('SIGTERM', () => {
            this.sdk.shutdown()
                .then(() => console.log('Tracing terminated'))
                .catch((error) => console.error('Error terminating tracing', error))
                .finally(() => process.exit(0));
        });
    }
    
    // Custom span creation
    createSpan(name, fn, attributes = {}) {
        const tracer = trace.getTracer(this.serviceName);
        return tracer.startActiveSpan(name, async (span) => {
            try {
                // Add custom attributes
                Object.entries(attributes).forEach(([key, value]) => {
                    span.setAttribute(key, value);
                });
                
                // Execute function
                const result = await fn(span);
                
                span.setStatus({ code: SpanStatusCode.OK });
                return result;
            } catch (error) {
                span.recordException(error);
                span.setStatus({
                    code: SpanStatusCode.ERROR,
                    message: error.message,
                });
                throw error;
            } finally {
                span.end();
            }
        });
    }
}

// Distributed tracing middleware
class TracingMiddleware {
    constructor() {
        this.tracer = trace.getTracer('http-middleware');
    }
    
    express() {
        return (req, res, next) => {
            const span = this.tracer.startSpan(`${req.method} ${req.path}`, {
                kind: SpanKind.SERVER,
                attributes: {
                    'http.method': req.method,
                    'http.url': req.url,
                    'http.target': req.path,
                    'http.host': req.hostname,
                    'http.scheme': req.protocol,
                    'http.user_agent': req.get('user-agent'),
                    'http.request_content_length': req.get('content-length'),
                },
            });
            
            // Inject trace context into request
            req.span = span;
            req.traceId = span.spanContext().traceId;
            
            // Add trace ID to response headers
            res.setHeader('X-Trace-Id', req.traceId);
            
            // Override res.end to capture response data
            const originalEnd = res.end;
            res.end = function(...args) {
                span.setAttribute('http.status_code', res.statusCode);
                span.setAttribute('http.response_content_length', res.get('content-length'));
                
                if (res.statusCode >= 400) {
                    span.setStatus({
                        code: SpanStatusCode.ERROR,
                        message: `HTTP ${res.statusCode}`,
                    });
                }
                
                span.end();
                originalEnd.apply(res, args);
            };
            
            next();
        };
    }
}

4. Debug Logging Framework

Implement structured debug logging:

Advanced Logger

// debug-logger.js
const winston = require('winston');
const { ElasticsearchTransport } = require('winston-elasticsearch');

class DebugLogger {
    constructor(options = {}) {
        this.service = options.service || 'app';
        this.level = process.env.LOG_LEVEL || 'debug';
        this.logger = this.createLogger();
    }
    
    createLogger() {
        const formats = [
            winston.format.timestamp(),
            winston.format.errors({ stack: true }),
            winston.format.splat(),
            winston.format.json(),
        ];
        
        if (process.env.NODE_ENV === 'development') {
            formats.push(winston.format.colorize());
            formats.push(winston.format.printf(this.devFormat));
        }
        
        const transports = [
            new winston.transports.Console({
                level: this.level,
                handleExceptions: true,
                handleRejections: true,
            }),
        ];
        
        // Add file transport for debugging
        if (process.env.DEBUG_LOG_FILE) {
            transports.push(
                new winston.transports.File({
                    filename: process.env.DEBUG_LOG_FILE,
                    level: 'debug',
                    maxsize: 10485760, // 10MB
                    maxFiles: 5,
                })
            );
        }
        
        // Add Elasticsearch for production
        if (process.env.ELASTICSEARCH_URL) {
            transports.push(
                new ElasticsearchTransport({
                    level: 'info',
                    clientOpts: {
                        node: process.env.ELASTICSEARCH_URL,
                    },
                    index: `logs-${this.service}`,
                })
            );
        }
        
        return winston.createLogger({
            level: this.level,
            format: winston.format.combine(...formats),
            defaultMeta: {
                service: this.service,
                environment: process.env.NODE_ENV,
                hostname: require('os').hostname(),
                pid: process.pid,
            },
            transports,
        });
    }
    
    devFormat(info) {
        const { timestamp, level, message, ...meta } = info;
        const metaString = Object.keys(meta).length ? 
            '\n' + JSON.stringify(meta, null, 2) : '';
        
        return `${timestamp} [${level}]: ${message}${metaString}`;
    }
    
    // Debug-specific methods
    trace(message, meta = {}) {
        const stack = new Error().stack;
        this.logger.debug(message, {
            ...meta,
            trace: stack,
            timestamp: Date.now(),
        });
    }
    
    timing(label, fn) {
        const start = process.hrtime.bigint();
        const result = fn();
        const end = process.hrtime.bigint();
        const duration = Number(end - start) / 1000000; // Convert to ms
        
        this.logger.debug(`Timing: ${label}`, {
            duration,
            unit: 'ms',
        });
        
        return result;
    }
    
    memory() {
        const usage = process.memoryUsage();
        this.logger.debug('Memory usage', {
            rss: `${Math.round(usage.rss / 1024 / 1024)}MB`,
            heapTotal: `${Math.round(usage.heapTotal / 1024 / 1024)}MB`,
            heapUsed: `${Math.round(usage.heapUsed / 1024 / 1024)}MB`,
            external: `${Math.round(usage.external / 1024 / 1024)}MB`,
        });
    }
}

// Debug context manager
class DebugContext {
    constructor() {
        this.contexts = new Map();
    }
    
    create(id, metadata = {}) {
        const context = {
            id,
            startTime: Date.now(),
            metadata,
            logs: [],
            spans: [],
        };
        
        this.contexts.set(id, context);
        return context;
    }
    
    log(contextId, level, message, data = {}) {
        const context = this.contexts.get(contextId);
        if (context) {
            context.logs.push({
                timestamp: Date.now(),
                level,
                message,
                data,
            });
        }
    }
    
    export(contextId) {
        const context = this.contexts.get(contextId);
        if (!context) return null;
        
        return {
            ...context,
            duration: Date.now() - context.startTime,
            logCount: context.logs.length,
        };
    }
}

5. Source Map Configuration

Set up source map support for production debugging:

Source Map Setup

// webpack.config.js
module.exports = {
    mode: 'production',
    devtool: 'hidden-source-map', // Generate source maps but don't reference them
    
    output: {
        filename: '[name].[contenthash].js',
        sourceMapFilename: 'sourcemaps/[name].[contenthash].js.map',
    },
    
    plugins: [
        // Upload source maps to error tracking service
        new SentryWebpackPlugin({
            authToken: process.env.SENTRY_AUTH_TOKEN,
            org: 'your-org',
            project: 'your-project',
            include: './dist',
            ignore: ['node_modules'],
            urlPrefix: '~/',
            release: process.env.RELEASE_VERSION,
            deleteAfterCompile: true,
        }),
    ],
};

// Runtime source map support
require('source-map-support').install({
    environment: 'node',
    handleUncaughtExceptions: false,
    retrieveSourceMap(source) {
        // Custom source map retrieval for production
        if (process.env.NODE_ENV === 'production') {
            const sourceMapUrl = getSourceMapUrl(source);
            if (sourceMapUrl) {
                const map = fetchSourceMap(sourceMapUrl);
                return {
                    url: source,
                    map: map,
                };
            }
        }
        return null;
    },
});

// Stack trace enhancement
Error.prepareStackTrace = (error, stack) => {
    const mapped = stack.map(frame => {
        const fileName = frame.getFileName();
        const lineNumber = frame.getLineNumber();
        const columnNumber = frame.getColumnNumber();
        
        // Try to get original position
        const original = getOriginalPosition(fileName, lineNumber, columnNumber);
        
        return {
            function: frame.getFunctionName() || '<anonymous>',
            file: original?.source || fileName,
            line: original?.line || lineNumber,
            column: original?.column || columnNumber,
            native: frame.isNative(),
            async: frame.isAsync(),
        };
    });
    
    return {
        message: error.message,
        stack: mapped,
    };
};

6. Performance Profiling

Implement performance profiling tools:

Performance Profiler

// performance-profiler.js
const v8Profiler = require('v8-profiler-next');
const fs = require('fs');
const path = require('path');

class PerformanceProfiler {
    constructor(options = {}) {
        this.outputDir = options.outputDir || './profiles';
        this.profiles = new Map();
        
        // Ensure output directory exists
        if (!fs.existsSync(this.outputDir)) {
            fs.mkdirSync(this.outputDir, { recursive: true });
        }
    }
    
    startCPUProfile(id, options = {}) {
        const title = options.title || `cpu-profile-${id}`;
        v8Profiler.startProfiling(title, true);
        
        this.profiles.set(id, {
            type: 'cpu',
            title,
            startTime: Date.now(),
        });
        
        return id;
    }
    
    stopCPUProfile(id) {
        const profileInfo = this.profiles.get(id);
        if (!profileInfo || profileInfo.type !== 'cpu') {
            throw new Error(`CPU profile ${id} not found`);
        }
        
        const profile = v8Profiler.stopProfiling(profileInfo.title);
        const duration = Date.now() - profileInfo.startTime;
        
        // Export profile
        const fileName = `${profileInfo.title}-${Date.now()}.cpuprofile`;
        const filePath = path.join(this.outputDir, fileName);
        
        profile.export((error, result) => {
            if (!error) {
                fs.writeFileSync(filePath, result);
                console.log(`CPU profile saved to ${filePath}`);
            }
            profile.delete();
        });
        
        this.profiles.delete(id);
        
        return {
            id,
            duration,
            filePath,
        };
    }
    
    takeHeapSnapshot(tag = '') {
        const fileName = `heap-${tag}-${Date.now()}.heapsnapshot`;
        const filePath = path.join(this.outputDir, fileName);
        
        const snapshot = v8Profiler.takeSnapshot();
        
        // Export snapshot
        snapshot.export((error, result) => {
            if (!error) {
                fs.writeFileSync(filePath, result);
                console.log(`Heap snapshot saved to ${filePath}`);
            }
            snapshot.delete();
        });
        
        return filePath;
    }
    
    measureFunction(fn, name = 'anonymous') {
        const measurements = {
            name,
            executions: 0,
            totalTime: 0,
            minTime: Infinity,
            maxTime: 0,
            avgTime: 0,
            lastExecution: null,
        };
        
        return new Proxy(fn, {
            apply(target, thisArg, args) {
                const start = process.hrtime.bigint();
                
                try {
                    const result = target.apply(thisArg, args);
                    
                    if (result instanceof Promise) {
                        return result.finally(() => {
                            this.recordExecution(start);
                        });
                    }
                    
                    this.recordExecution(start);
                    return result;
                } catch (error) {
                    this.recordExecution(start);
                    throw error;
                }
            },
            
            recordExecution(start) {
                const end = process.hrtime.bigint();
                const duration = Number(end - start) / 1000000; // Convert to ms
                
                measurements.executions++;
                measurements.totalTime += duration;
                measurements.minTime = Math.min(measurements.minTime, duration);
                measurements.maxTime = Math.max(measurements.maxTime, duration);
                measurements.avgTime = measurements.totalTime / measurements.executions;
                measurements.lastExecution = new Date();
                
                // Log slow executions
                if (duration > 100) {
                    console.warn(`Slow function execution: ${name} took ${duration}ms`);
                }
            },
            
            get(target, prop) {
                if (prop === 'measurements') {
                    return measurements;
                }
                return target[prop];
            },
        });
    }
}

// Memory leak detector
class MemoryLeakDetector {
    constructor() {
        this.snapshots = [];
        this.threshold = 50 * 1024 * 1024; // 50MB
    }
    
    start(interval = 60000) {
        this.interval = setInterval(() => {
            this.checkMemory();
        }, interval);
    }
    
    checkMemory() {
        const usage = process.memoryUsage();
        const snapshot = {
            timestamp: Date.now(),
            heapUsed: usage.heapUsed,
            external: usage.external,
            rss: usage.rss,
        };
        
        this.snapshots.push(snapshot);
        
        // Keep only last 10 snapshots
        if (this.snapshots.length > 10) {
            this.snapshots.shift();
        }
        
        // Check for memory leak pattern
        if (this.snapshots.length >= 5) {
            const trend = this.calculateTrend();
            if (trend.increasing && trend.delta > this.threshold) {
                console.error('Potential memory leak detected!', {
                    trend,
                    current: snapshot,
                });
                
                // Take heap snapshot for analysis
                const profiler = new PerformanceProfiler();
                profiler.takeHeapSnapshot('leak-detection');
            }
        }
    }
    
    calculateTrend() {
        const recent = this.snapshots.slice(-5);
        const first = recent[0];
        const last = recent[recent.length - 1];
        
        const delta = last.heapUsed - first.heapUsed;
        const increasing = recent.every((s, i) => 
            i === 0 || s.heapUsed > recent[i - 1].heapUsed
        );
        
        return {
            increasing,
            delta,
            rate: delta / (last.timestamp - first.timestamp) * 1000 * 60, // MB per minute
        };
    }
}

7. Debug Configuration Management

Centralize debug configurations:

Debug Configuration

// debug-config.js
class DebugConfiguration {
    constructor() {
        this.config = {
            // Debug levels
            levels: {
                error: 0,
                warn: 1,
                info: 2,
                debug: 3,
                trace: 4,
            },
            
            // Feature flags
            features: {
                remoteDebugging: process.env.ENABLE_REMOTE_DEBUG === 'true',
                tracing: process.env.ENABLE_TRACING === 'true',
                profiling: process.env.ENABLE_PROFILING === 'true',
                memoryMonitoring: process.env.ENABLE_MEMORY_MONITORING === 'true',
            },
            
            // Debug endpoints
            endpoints: {
                jaeger: process.env.JAEGER_ENDPOINT || 'http://localhost:14268',
                elasticsearch: process.env.ELASTICSEARCH_URL || 'http://localhost:9200',
                sentry: process.env.SENTRY_DSN,
            },
            
            // Sampling rates
            sampling: {
                traces: parseFloat(process.env.TRACE_SAMPLING_RATE || '0.1'),
                profiles: parseFloat(process.env.PROFILE_SAMPLING_RATE || '0.01'),
                logs: parseFloat(process.env.LOG_SAMPLING_RATE || '1.0'),
            },
        };
    }
    
    isEnabled(feature) {
        return this.config.features[feature] || false;
    }
    
    getLevel() {
        const level = process.env.DEBUG_LEVEL || 'info';
        return this.config.levels[level] || 2;
    }
    
    shouldSample(type) {
        const rate = this.config.sampling[type] || 1.0;
        return Math.random() < rate;
    }
}

// Debug middleware factory
class DebugMiddlewareFactory {
    static create(app, config) {
        const middlewares = [];
        
        if (config.isEnabled('tracing')) {
            const tracingMiddleware = new TracingMiddleware();
            middlewares.push(tracingMiddleware.express());
        }
        
        if (config.isEnabled('profiling')) {
            middlewares.push(this.profilingMiddleware());
        }
        
        if (config.isEnabled('memoryMonitoring')) {
            const detector = new MemoryLeakDetector();
            detector.start();
        }
        
        // Debug routes
        if (process.env.NODE_ENV === 'development') {
            app.get('/debug/heap', (req, res) => {
                const profiler = new PerformanceProfiler();
                const path = profiler.takeHeapSnapshot('manual');
                res.json({ heapSnapshot: path });
            });
            
            app.get('/debug/profile', async (req, res) => {
                const profiler = new PerformanceProfiler();
                const id = profiler.startCPUProfile('manual');
                
                setTimeout(() => {
                    const result = profiler.stopCPUProfile(id);
                    res.json(result);
                }, 10000);
            });
            
            app.get('/debug/metrics', (req, res) => {
                res.json({
                    memory: process.memoryUsage(),
                    cpu: process.cpuUsage(),
                    uptime: process.uptime(),
                });
            });
        }
        
        return middlewares;
    }
    
    static profilingMiddleware() {
        const profiler = new PerformanceProfiler();
        
        return (req, res, next) => {
            if (Math.random() < 0.01) { // 1% sampling
                const id = profiler.startCPUProfile(`request-${Date.now()}`);
                
                res.on('finish', () => {
                    profiler.stopCPUProfile(id);
                });
            }
            
            next();
        };
    }
}

8. Production Debugging

Enable safe production debugging:

Production Debug Tools

// production-debug.js
class ProductionDebugger {
    constructor(options = {}) {
        this.enabled = process.env.PRODUCTION_DEBUG === 'true';
        this.authToken = process.env.DEBUG_AUTH_TOKEN;
        this.allowedIPs = (process.env.DEBUG_ALLOWED_IPS || '').split(',');
    }
    
    middleware() {
        return (req, res, next) => {
            if (!this.enabled) {
                return next();
            }
            
            // Check authorization
            const token = req.headers['x-debug-token'];
            const ip = req.ip || req.connection.remoteAddress;
            
            if (token !== this.authToken || !this.allowedIPs.includes(ip)) {
                return next();
            }
            
            // Add debug headers
            res.setHeader('X-Debug-Enabled', 'true');
            
            // Enable debug mode for this request
            req.debugMode = true;
            req.debugContext = new DebugContext().create(req.id);
            
            // Override console for this request
            const originalConsole = { ...console };
            ['log', 'debug', 'info', 'warn', 'error'].forEach(method => {
                console[method] = (...args) => {
                    req.debugContext.log(req.id, method, args[0], args.slice(1));
                    originalConsole[method](...args);
                };
            });
            
            // Restore console on response
            res.on('finish', () => {
                Object.assign(console, originalConsole);
                
                // Send debug info if requested
                if (req.headers['x-debug-response'] === 'true') {
                    const debugInfo = req.debugContext.export(req.id);
                    res.setHeader('X-Debug-Info', JSON.stringify(debugInfo));
                }
            });
            
            next();
        };
    }
}

// Conditional breakpoints in production
class ConditionalBreakpoint {
    constructor(condition, callback) {
        this.condition = condition;
        this.callback = callback;
        this.hits = 0;
    }
    
    check(context) {
        if (this.condition(context)) {
            this.hits++;
            
            // Log breakpoint hit
            console.debug('Conditional breakpoint hit', {
                condition: this.condition.toString(),
                hits: this.hits,
                context,
            });
            
            // Execute callback
            if (this.callback) {
                this.callback(context);
            }
            
            // In production, don't actually break
            if (process.env.NODE_ENV === 'production') {
                // Take snapshot instead
                const profiler = new PerformanceProfiler();
                profiler.takeHeapSnapshot(`breakpoint-${Date.now()}`);
            } else {
                // In development, use debugger
                debugger;
            }
        }
    }
}

// Usage
const breakpoints = new Map();

// Set conditional breakpoint
breakpoints.set('high-memory', new ConditionalBreakpoint(
    (context) => context.memoryUsage > 500 * 1024 * 1024, // 500MB
    (context) => {
        console.error('High memory usage detected', context);
        // Send alert
        alerting.send('high-memory', context);
    }
));

// Check breakpoints in code
function checkBreakpoints(context) {
    breakpoints.forEach(breakpoint => {
        breakpoint.check(context);
    });
}

9. Debug Dashboard

Create a debug dashboard for monitoring:

Debug Dashboard

<!-- debug-dashboard.html -->
<!DOCTYPE html>
<html>
<head>
    <title>Debug Dashboard</title>
    <style>
        body { font-family: monospace; background: #1e1e1e; color: #d4d4d4; }
        .container { max-width: 1200px; margin: 0 auto; padding: 20px; }
        .metric { background: #252526; padding: 15px; margin: 10px 0; border-radius: 5px; }
        .metric h3 { margin: 0 0 10px 0; color: #569cd6; }
        .chart { height: 200px; background: #1e1e1e; margin: 10px 0; }
        .log-entry { padding: 5px; border-bottom: 1px solid #3e3e3e; }
        .error { color: #f44747; }
        .warn { color: #ff9800; }
        .info { color: #4fc3f7; }
        .debug { color: #4caf50; }
    </style>
</head>
<body>
    <div class="container">
        <h1>Debug Dashboard</h1>
        
        <div class="metric">
            <h3>System Metrics</h3>
            <div id="metrics"></div>
        </div>
        
        <div class="metric">
            <h3>Memory Usage</h3>
            <canvas id="memoryChart" class="chart"></canvas>
        </div>
        
        <div class="metric">
            <h3>Request Traces</h3>
            <div id="traces"></div>
        </div>
        
        <div class="metric">
            <h3>Debug Logs</h3>
            <div id="logs"></div>
        </div>
    </div>
    
    <script>
        // WebSocket connection for real-time updates
        const ws = new WebSocket('ws://localhost:9231/debug');
        
        ws.onmessage = (event) => {
            const data = JSON.parse(event.data);
            
            switch (data.type) {
                case 'metrics':
                    updateMetrics(data.payload);
                    break;
                case 'trace':
                    addTrace(data.payload);
                    break;
                case 'log':
                    addLog(data.payload);
                    break;
            }
        };
        
        function updateMetrics(metrics) {
            const container = document.getElementById('metrics');
            container.innerHTML = `
                <div>CPU: ${metrics.cpu.percent}%</div>
                <div>Memory: ${metrics.memory.used}MB / ${metrics.memory.total}MB</div>
                <div>Uptime: ${metrics.uptime}s</div>
                <div>Active Requests: ${metrics.activeRequests}</div>
            `;
        }
        
        function addTrace(trace) {
            const container = document.getElementById('traces');
            const entry = document.createElement('div');
            entry.className = 'log-entry';
            entry.innerHTML = `
                <span>${trace.timestamp}</span>
                <span>${trace.method} ${trace.path}</span>
                <span>${trace.duration}ms</span>
                <span>${trace.status}</span>
            `;
            container.insertBefore(entry, container.firstChild);
        }
        
        function addLog(log) {
            const container = document.getElementById('logs');
            const entry = document.createElement('div');
            entry.className = `log-entry ${log.level}`;
            entry.innerHTML = `
                <span>${log.timestamp}</span>
                <span>[${log.level.toUpperCase()}]</span>
                <span>${log.message}</span>
            `;
            container.insertBefore(entry, container.firstChild);
            
            // Keep only last 100 logs
            while (container.children.length > 100) {
                container.removeChild(container.lastChild);
            }
        }
        
        // Memory usage chart
        const memoryChart = document.getElementById('memoryChart').getContext('2d');
        const memoryData = [];
        
        function updateMemoryChart(usage) {
            memoryData.push({
                time: new Date(),
                value: usage,
            });
            
            // Keep last 50 points
            if (memoryData.length > 50) {
                memoryData.shift();
            }
            
            // Draw chart
            // ... chart drawing logic
        }
    </script>
</body>
</html>

10. IDE Integration

Configure IDE debugging features:

IDE Debug Extensions

// .vscode/extensions.json
{
    "recommendations": [
        "ms-vscode.vscode-js-debug",
        "msjsdiag.debugger-for-chrome",
        "ms-vscode.vscode-typescript-tslint-plugin",
        "dbaeumer.vscode-eslint",
        "ms-azuretools.vscode-docker",
        "humao.rest-client",
        "eamodio.gitlens",
        "usernamehw.errorlens",
        "wayou.vscode-todo-highlight",
        "formulahendry.code-runner"
    ]
}

// .vscode/tasks.json
{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "Start Debug Server",
            "type": "npm",
            "script": "debug",
            "problemMatcher": [],
            "presentation": {
                "reveal": "always",
                "panel": "dedicated"
            }
        },
        {
            "label": "Profile Application",
            "type": "shell",
            "command": "node --inspect-brk --cpu-prof --cpu-prof-dir=./profiles ${workspaceFolder}/src/index.js

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