Monitoring & Observability

Comprehensive monitoring, observability, and alerting strategies for production systems.

Three Pillars of Observability

Metrics

• Quantitative measurements (counters, gauges, histograms)
• Time-series data (Prometheus, InfluxDB, Datadog)
• Examples: request latency, error rate, CPU usage

Logs

• Structured event records
• Searchable and filterable
• Examples: application logs, access logs, error logs

Traces

• Request flow through system
• Distributed tracing (Jaeger, Zipkin)
• Shows dependencies and bottlenecks

Implementation Approaches

Metrics Collection

from prometheus_client import Counter, Histogram

request_count = Counter('http_requests_total', 'Total requests')
latency = Histogram('http_request_duration_seconds', 'Request latency')

@app.route('/api/users')
def get_users():
    request_count.inc()
    with latency.time():
        return fetch_users()

Structured Logging

{
  "timestamp": "2025-02-07T10:30:00Z",
  "level": "ERROR",
  "service": "user-service",
  "request_id": "req_12345",
  "user_id": "user_789",
  "error_code": "DB_CONNECTION_FAILED",
  "message": "Failed to connect to database",
  "duration_ms": 1500
}

Distributed Tracing

• Instrument application code
• Propagate trace IDs across services
• Collect traces centrally (Jaeger, Zipkin)
• Visualize service dependencies

Popular Tools

Best Practices

1. Structured Logging – JSON format with context
2. Contextual Data – Request IDs, user IDs, service names
3. Sampling – Don’t log everything to save costs
4. Retention Policy – Balance cost and retention needs
5. Alerts – On error rates, latency, resource usage
6. Dashboards – Visualize key metrics
7. Runbooks – Document how to respond to alerts

Key Metrics to Monitor

• Request rate and latency (p50, p95, p99)
• Error rate and error types
• Resource usage (CPU, memory, disk)
• Database query performance
• Cache hit rates
• Queue depths
• User session counts

References

• Prometheus Monitoring Best Practices
• Observability Engineering (O’Reilly)
• Google SRE Book
• ELK Stack Documentation
• OpenTelemetry Project