Privacy-focused error tracking and performance monitoring using Sentry. Opt-in design with automatic data sanitization to protect sensitive information.

Core Purpose

• Provide opt-in error tracking
• Sanitize sensitive data automatically
• Capture performance metrics
• Enable debugging with breadcrumbs

Configuration

Environment Variables

Variable	Default	Description
MONITORING_ENABLED	false	Enable/disable monitoring
SENTRY_DSN	-	Sentry project DSN*
SENTRY_ENVIRONMENT	NODE_ENV	Environment name
SENTRY_TRACES_SAMPLE_RATE	0.1	Performance sampling

*Required when monitoring is enabled

Key Functions

Check Status

export function isMonitoringEnabled(): boolean {
    return process.env.MONITORING_ENABLED === 'true' && !!process.env.SENTRY_DSN;
}

Setup Express

// Before routes
setupExpressRequestHandler(app);

// After routes
setupExpressErrorHandler(app);
app.use(createErrorHandler());

Capture Errors

export function captureException(
    error: Error, 
    context?: Record<string, unknown>
): void {
    if (!isMonitoringEnabled()) return;
    
    Sentry.captureException(error, {
        extra: sanitizeData(context || {})
    });
}

Add Breadcrumbs

export function addBreadcrumb(
    message: string,
    category: string,
    data?: Record<string, unknown>
): void {
    if (!isMonitoringEnabled()) return;
    
    Sentry.addBreadcrumb({
        message,
        category,
        level: 'info',
        data: sanitizeData(data || {})
    });
}

Integration in Application

Express Setup

import { 
    setupExpressRequestHandler,
    setupExpressErrorHandler,
    createErrorHandler,
    logMonitoringStatus 
} from './utils/monitoring.js';

const app = express();

// Log status
logMonitoringStatus();

// Setup request handler (first)
setupExpressRequestHandler(app);

// Routes
app.use('/api', apiRoutes);

// Setup error handlers (last)
setupExpressErrorHandler(app);
app.use(createErrorHandler());

Service Integration

export class ScanService {
    async scanContent(content: string) {
        addBreadcrumb('Scan requested', 'scan', {
            contentSize: content.length
        });

        try {
            const result = await this.client.scan(content);
            return result;
        } catch (error) {
            captureException(error, {
                service: 'ScanService',
                operation: 'scanContent'
            });
            throw error;
        }
    }
}

Data Sanitization

Automatic removal of sensitive data:

const sensitiveKeys = [
    'token', 'key', 'secret', 'password', 
    'auth', 'api', 'credential', 'private'
];

// Example sanitization
{
    userId: '12345',
    apiKey: 'secret-key',     // → '[REDACTED]'
    password: 'pass123'       // → '[REDACTED]'
}

Privacy Features

What IS Captured

• Error messages and stack traces
• HTTP method, path, query params
• Custom breadcrumbs and context
• Application metadata

What is NOT Captured

• Request/response bodies
• HTTP headers (auth headers)
• API keys or credentials
• Personal information
• File contents

Error Response

When monitoring is enabled:

{
    "error": "Internal server error",
    "errorId": "abc123def456",
    "timestamp": "2024-01-15T10:30:00.000Z"
}

Best Practices

Meaningful Breadcrumbs

// Good
addBreadcrumb('Payment processed', 'payment', {
    amount: payment.amount,
    method: payment.method
});

// Bad
addBreadcrumb('Action', 'generic');

Structured Context

// Good
captureException(error, {
    component: 'PaymentService',
    operation: 'processPayment',
    paymentId: payment.id
});

Environment Sampling

# Production - conservative
SENTRY_TRACES_SAMPLE_RATE=0.01  # 1%

# Staging - moderate
SENTRY_TRACES_SAMPLE_RATE=0.1   # 10%

# Development - full
SENTRY_TRACES_SAMPLE_RATE=1.0   # 100%

Performance Monitoring

Custom sampling logic:

tracesSampler(context) {
    // Skip health checks
    if (context.request?.url?.includes('/health')) {
        return 0;
    }
    
    // Lower rate for SSE
    if (context.request?.url?.includes('/sse')) {
        return 0.01; // 1%
    }
    
    return 0.1; // Default 10%
}

Related Modules

• Instrument - Sentry initialization
• Logger - Logging integration
• Main Application - Express setup
• Configuration - Environment config