Production Monitoring Guardian

Mission: Ensure you know what's happening in production BEFORE your users do. Establish proactive monitoring that catches issues early, enables fast debugging, and prevents revenue loss.

Activation Triggers

• Deploying to production for the first time
• "How do I know if my app is down?"
• Performance degradation reports
• Unexplained errors or downtime
• Capacity planning needs
• Incident response preparation
• SLA/uptime requirements
• Customer reports issues before you

The Four Pillars of Observability

1. Metrics - What's happening? (CPU, memory, request rate, error rate)
2. Logs - Why is it happening? (Error messages, stack traces, context)
3. Traces - Where is it happening? (Request flow through system)
4. Alerts - When should I act? (Thresholds, escalation policies)

Scan Methodology

1. Initial Context Gathering

Ask if not provided:

• "Is your application in production?"
• "What's your current monitoring setup?" (none, partial, comprehensive)
• "What's your uptime requirement?" (99%, 99.9%, 99.99%)
• "How do you currently know if something breaks?"
• "What's your incident response process?"

2. Monitoring Maturity Assessment

Level 0: Blind 🔴 CRITICAL RISK

• No monitoring
• Users report outages
• No error tracking
• No performance visibility
• Risk: Revenue loss, customer churn, reputation damage

Level 1: Basic 🟡 HIGH RISK

• Simple uptime checks (ping endpoints)
• Basic server metrics (CPU, memory)
• Manual log checking
• Risk: Delayed incident response, no root cause analysis

Level 2: Operational 🟢 ACCEPTABLE

• Error tracking (Sentry)
• Uptime monitoring (UptimeRobot)
• Log aggregation
• Basic alerting
• Risk: Minimal, can operate safely

Level 3: Advanced ⭐ OPTIMAL

• Full observability (metrics + logs + traces)
• Proactive alerting
• Performance monitoring (APM)
• Auto-scaling based on metrics
• Dashboards for all stakeholders
• Risk: Very low, enterprise-grade

PDFLab Current State: Level 0-1 (Production deployed, monitoring incomplete)

3. Critical Monitoring Components

🔴 CRITICAL: Error Tracking (Sentry)

Why Essential:

• Catches errors before users report them
• Provides stack traces and context
• Tracks error frequency and impact
• Enables quick debugging

Setup for PDFLab:

# Install Sentry
cd backend
npm install @sentry/node @sentry/profiling-node

cd ..
npm install @sentry/nextjs

Backend Integration (Express.js):

// backend/src/server.ts
import * as Sentry from '@sentry/node'
import { ProfilingIntegration } from '@sentry/profiling-node'

// Initialize Sentry FIRST (before any other imports)
Sentry.init({
  dsn: process.env.SENTRY_DSN,
  environment: process.env.NODE_ENV || 'development',
  integrations: [
    new ProfilingIntegration(),
    new Sentry.Integrations.Http({ tracing: true }),
    new Sentry.Integrations.Express({ app })
  ],
  tracesSampleRate: 0.1, // 10% of transactions
  profilesSampleRate: 0.1,

  // Filter sensitive data
  beforeSend(event) {
    // Remove passwords from error data
    if (event.request) {
      delete event.request.cookies
      if (event.request.data?.password) {
        event.request.data.password = '[REDACTED]'
      }
    }
    return event
  }
})

// Sentry request handler (BEFORE routes)
app.use(Sentry.Handlers.requestHandler())
app.use(Sentry.Handlers.tracingHandler())

// ... your routes ...

// Sentry error handler (AFTER routes, BEFORE other error handlers)
app.use(Sentry.Handlers.errorHandler())

// Custom error handler
app.use((err: Error, req: Request, res: Response, next: NextFunction) => {
  // Sentry already captured error
  console.error('Unhandled error:', err)

  res.status(500).json({
    error: 'Internal server error',
    message: process.env.NODE_ENV === 'development' ? err.message : 'Something went wrong',
    sentry_id: res.sentry // Error ID for support tickets
  })
})

Frontend Integration (Next.js):

// sentry.client.config.ts
import * as Sentry from '@sentry/nextjs'

Sentry.init({
  dsn: process.env.NEXT_PUBLIC_SENTRY_DSN,
  environment: process.env.NODE_ENV,
  tracesSampleRate: 0.1,

  // Filter PII
  beforeSend(event, hint) {
    // Don't send auth tokens
    if (event.request?.headers) {
      delete event.request.headers.authorization
    }
    return event
  }
})

// Usage in components:
try {
  await pdflabAPI.uploadBatch(files, operation, options)
} catch (error) {
  Sentry.captureException(error, {
    tags: {
      feature: 'batch_upload',
      operation: operation
    },
    extra: {
      file_count: files.length,
      total_size: files.reduce((sum, f) => sum + f.size, 0)
    }
  })
  throw error
}

Environment Variables:

# .env (backend)
SENTRY_DSN=https://xxx@xxx.ingest.sentry.io/xxx

# .env.local (frontend)
NEXT_PUBLIC_SENTRY_DSN=https://xxx@xxx.ingest.sentry.io/xxx

Verification:

// Test Sentry integration
app.get('/debug-sentry', (req, res) => {
  throw new Error('Test Sentry error tracking')
})

// Visit http://localhost:3006/debug-sentry
// Check Sentry dashboard for error

🔴 CRITICAL: Uptime Monitoring (UptimeRobot)

Why Essential:

• Detects when site is down
• Monitors from external location (not your server)
• Alerts via SMS/email/Slack
• Tracks uptime percentage for SLAs

Setup (5 minutes, FREE):

1. Create UptimeRobot Account

   • Go to https://uptimerobot.com
   • Free tier: 50 monitors, 5-minute intervals

2. Add HTTP Monitor

   Monitor Type: HTTP(s)
   Friendly Name: PDFLab Production
   URL: https://pdflab.pro
   Monitoring Interval: 5 minutes (free tier)
   
   Advanced:
   - Check for keyword: "PDFLab" (ensures page loads correctly)
   - Timeout: 30 seconds
   

3. Add Health Check Endpoint Monitor

   Monitor Type: HTTP(s)
   Friendly Name: PDFLab API Health
   URL: https://pdflab.pro/health
   Monitoring Interval: 5 minutes
   Expected Status: 200
   
   POST-Value (for detailed check):
   Check for JSON: "status":"healthy"
   

4. Configure Alerts

   Email: your@email.com
   SMS: +1-xxx-xxx-xxxx (optional, paid)
   Slack: webhook URL (recommended)
   
   Alert When:
   - Down (site unreachable)
   - Up (site back online)
   - Slow response (>5s)
   

5. Test Alerts

   # Stop backend to trigger alert
   docker stop pdflab-backend
   
   # Wait 5-10 minutes for UptimeRobot to detect
   # Verify you receive alert
   
   # Restart backend
   docker start pdflab-backend
   
   # Verify "Up" alert
   

Advanced Health Checks:

// backend/src/server.ts
app.get('/health', async (req, res) => {
  const health = {
    status: 'healthy',
    timestamp: new Date().toISOString(),
    uptime: process.uptime(),
    checks: {
      database: 'unknown',
      redis: 'unknown',
      cloudconvert: 'unknown'
    }
  }

  try {
    // Check database
    await sequelize.authenticate()
    health.checks.database = 'healthy'
  } catch {
    health.checks.database = 'unhealthy'
    health.status = 'degraded'
  }

  try {
    // Check Redis
    await redisClient.ping()
    health.checks.redis = 'healthy'
  } catch {
    health.checks.redis = 'unhealthy'
    health.status = 'degraded'
  }

  const statusCode = health.status === 'healthy' ? 200 : 503
  res.status(statusCode).json(health)
})

🟡 HIGH: Log Aggregation

Why Important:

• Centralized log viewing
• Search across all servers
• Correlate logs with errors
• Compliance/audit requirements

Simple Pattern (File-based):

// backend/src/utils/logger.ts
import winston from 'winston'

const logger = winston.createLogger({
  level: process.env.LOG_LEVEL || 'info',
  format: winston.format.combine(
    winston.format.timestamp(),
    winston.format.errors({ stack: true }),
    winston.format.json()
  ),
  transports: [
    // Console (for Docker logs)
    new winston.transports.Console({
      format: winston.format.simple()
    }),

    // File (for persistence)
    new winston.transports.File({
      filename: 'logs/error.log',
      level: 'error'
    }),
    new winston.transports.File({
      filename: 'logs/combined.log'
    })
  ]
})

export default logger

// Usage:
logger.info('Batch processing started', {
  batch_id: batchId,
  user_id: userId,
  file_count: files.length
})

logger.error('Conversion failed', {
  batch_id: batchId,
  error: error.message,
  stack: error.stack
})

Structured Logging Pattern:

// Always log with context
logger.info('Event description', {
  // Standard fields
  user_id: req.user?.id,
  request_id: req.id,
  ip_address: req.ip,

  // Event-specific fields
  batch_id: batchId,
  operation: 'batch_upload',
  file_count: 5,

  // Metrics
  duration_ms: Date.now() - startTime,
  success: true
})

Log Levels:

• error - Something failed, needs attention
• warn - Something suspicious, might need attention
• info - Normal operation, important events
• http - HTTP request/response (verbose)
• debug - Detailed debugging info (development only)

🟡 HIGH: Performance Monitoring (APM)

Why Important:

• Identify slow endpoints
• Database query optimization
• Memory leak detection
• Capacity planning

Simple APM (Built-in Node.js):

// backend/src/middleware/performance.middleware.ts
export const performanceMiddleware = (req: Request, res: Response, next: NextFunction) => {
  const start = Date.now()

  // Capture response finish
  res.on('finish', () => {
    const duration = Date.now() - start

    // Log slow requests
    if (duration > 1000) {
      logger.warn('Slow request', {
        method: req.method,
        url: req.url,
        duration_ms: duration,
        status: res.statusCode
      })
    }

    // Track metrics
    metrics.histogram('http.request.duration', duration, {
      method: req.method,
      route: req.route?.path,
      status: res.statusCode
    })
  })

  next()
}

app.use(performanceMiddleware)

Database Query Monitoring:

// backend/src/config/database.ts
export const sequelize = new Sequelize({
  // ... other config ...

  logging: (sql, timing) => {
    if (timing && timing > 100) {
      logger.warn('Slow query', {
        sql,
        duration_ms: timing
      })
    }
  },

  benchmark: true // Enable timing
})

🟠 MEDIUM: Application Metrics

Key Metrics to Track:

// backend/src/utils/metrics.ts
class Metrics {
  private metrics = new Map<string, number>()

  increment(name: string, tags: Record<string, string> = {}) {
    const key = `${name}:${JSON.stringify(tags)}`
    this.metrics.set(key, (this.metrics.get(key) || 0) + 1)
  }

  gauge(name: string, value: number, tags: Record<string, string> = {}) {
    const key = `${name}:${JSON.stringify(tags)}`
    this.metrics.set(key, value)
  }

  // Export for monitoring systems
  getAll() {
    return Object.fromEntries(this.metrics)
  }
}

export const metrics = new Metrics()

// Usage throughout application:

// Conversion job started
metrics.increment('conversion.job.started', {
  type: 'pdf_to_pptx',
  user_plan: user.plan
})

// Conversion job completed
metrics.increment('conversion.job.completed', {
  type: 'pdf_to_pptx'
})

// Conversion job failed
metrics.increment('conversion.job.failed', {
  type: 'pdf_to_pptx',
  error_type: 'cloudconvert_timeout'
})

// Active users
metrics.gauge('users.active', await getActiveUserCount())

// Queue depth
metrics.gauge('queue.depth', await conversionQueue.count())

Metrics Endpoint:

// Expose metrics for Prometheus/monitoring
app.get('/metrics', (req, res) => {
  res.json({
    timestamp: new Date().toISOString(),
    metrics: metrics.getAll(),
    system: {
      memory: process.memoryUsage(),
      uptime: process.uptime(),
      cpu: process.cpuUsage()
    }
  })
})

4. Alerting Strategy

Alert Fatigue Prevention:

• Don't alert on everything
• Use severity levels (P1=critical, P2=high, P3=medium, P4=low)
• Escalate if not acknowledged
• Group related alerts

Critical Alerts (Wake up at 3am):

• Site down (5+ minute outage)
• Database unreachable
• Error rate >10%
• Payment processing failed
• Disk usage >90%

High Priority Alerts (Check within 1 hour):

• Error rate >5%
• Slow response times (P95 >5s)
• Queue backing up (>100 jobs pending)
• CloudConvert API errors

Medium Priority Alerts (Check during business hours):

• Warning logs increasing
• Memory usage trending up
• Unusual traffic patterns

Alert Channels:

Critical (P1):
  → SMS to on-call engineer
  → Slack #incidents channel
  → PagerDuty escalation

High (P2):
  → Slack #alerts channel
  → Email to team

Medium (P3):
  → Slack #monitoring channel
  → Daily digest email

5. Dashboard Design

Essential Dashboards:

1. Service Health Dashboard (Operations)

┌─────────────────────────────────────┐
│  PDFLab Production Status           │
├─────────────────────────────────────┤
│  Uptime (24h):      99.95% ✅       │
│  Error Rate (1h):   0.2%   ✅       │
│  Avg Response:      245ms  ✅       │
│  Active Users:      127             │
│  Conversion Queue:  3 jobs          │
│                                     │
│  Component Status:                  │
│  • Frontend:        ✅ Healthy      │
│  • Backend API:     ✅ Healthy      │
│  • Database:        ✅ Healthy      │
│  • Redis:           ✅ Healthy      │
│  • CloudConvert:    ⚠️  Slow (3s)   │
└─────────────────────────────────────┘

2. Business Metrics Dashboard (Executives)

┌─────────────────────────────────────┐
│  PDFLab Business Metrics            │
├─────────────────────────────────────┤
│  Today:                             │
│  • Conversions:     342  (+12%)     │
│  • New Users:       23   (+5%)      │
│  • Revenue:         $156 (+8%)      │
│                                     │
│  This Month:                        │
│  • MRR:             $1,247          │
│  • Active Users:    892             │
│  • Churn Rate:      3.2%            │
│                                     │
│  Popular Features:                  │
│  1. PDF → PPTX      45%             │
│  2. PDF → DOCX      32%             │
│  3. PDF Compress    18%             │
└─────────────────────────────────────┘

3. Performance Dashboard (Developers)

┌─────────────────────────────────────┐
│  API Performance                    │
├─────────────────────────────────────┤
│  Request Duration (P95):            │
│  /api/upload        423ms  ⚠️       │
│  /api/status        87ms   ✅       │
│  /api/download      1.2s   ❌       │
│                                     │
│  Database Queries (P95):            │
│  Users.findByPk     12ms   ✅       │
│  Jobs.findAll       156ms  ⚠️       │
│                                     │
│  Memory Usage:                      │
│  Heap Used:         324MB  ✅       │
│  Heap Total:        512MB           │
│  RSS:               478MB  ✅       │
└─────────────────────────────────────┘

6. Incident Response Playbook

When Alert Fires:

1. Acknowledge (1 minute)

   • Click "Acknowledge" in PagerDuty/Slack
   • Prevents escalation

2. Assess (5 minutes)

   • Check Sentry for recent errors
   • Check UptimeRobot for uptime status
   • Check server metrics (CPU, memory, disk)
   • Check logs for patterns

3. Mitigate (15 minutes)

   • If site down: restart services
   • If database down: check connections, restart MySQL
   • If queue backed up: add workers or pause intake
   • If CloudConvert down: show maintenance message

4. Communicate (ongoing)

   • Update status page
   • Notify affected users
   • Internal Slack updates

5. Resolve (variable)

   • Fix root cause
   • Verify fix in production
   • Monitor for recurrence

6. Post-Mortem (24 hours later)

   • Document what happened
   • Identify root cause
   • Create prevention tasks
   • Share learnings

Production Monitoring Checklist

Essential (Deploy with these)

• Sentry error tracking configured
• UptimeRobot monitoring pdflab.pro
• Health check endpoint (/health)
• Structured logging with Winston
• Alert for site down (email/SMS)

Important (Add within first month)

• Performance monitoring (slow requests logged)
• Database query monitoring
• Business metrics tracking
• Dashboard for operations team
• Incident response playbook documented

Advanced (Add as you scale)

• Distributed tracing (Sentry Traces)
• Custom metrics (conversion rates, revenue)
• Auto-scaling based on metrics
• Anomaly detection (ML-based alerting)
• Real user monitoring (RUM)

Quick Setup (30 minutes)

# 1. Sentry (10 min)
npm install @sentry/node @sentry/nextjs
# Add initialization code (see above)
# Test with /debug-sentry endpoint

# 2. UptimeRobot (5 min)
# Sign up at https://uptimerobot.com
# Add pdflab.pro monitor
# Configure email alerts

# 3. Health Check (5 min)
# Add /health endpoint (see above)
# Test: curl https://pdflab.pro/health

# 4. Logging (10 min)
npm install winston
# Add structured logging (see above)
# Verify logs: tail -f logs/combined.log

Key Principles

1. Monitor user-facing metrics - Uptime, error rate, performance
2. Alert on symptoms, not causes - "Site down" not "CPU high"
3. Make alerts actionable - Include fix suggestions
4. Prevent alert fatigue - Only critical alerts wake people up
5. Document incident response - Playbooks save time
6. Review metrics regularly - Weekly ops review
7. Continuous improvement - Add monitoring as you learn

Monitoring ROI

Cost:

• Sentry: $0-26/month (free tier sufficient for PDFLab)
• UptimeRobot: $0-7/month (free tier sufficient)
• Time: 2-4 hours initial setup
• Total: ~$0-50/month

Benefits:

• Detect outages in 5 minutes (vs 5 hours from user reports)
• Reduce MTTR from hours to minutes
• Prevent revenue loss from undetected issues
• Build customer trust with transparent status
• ROI: 10-100x (one prevented outage pays for years of monitoring)

When to Escalate

• Distributed tracing needs (microservices)
• Custom monitoring dashboards
• SLA/SLO definition
• On-call rotation setup
• Runbook automation
• Chaos engineering