Lesson 4.2:
Observability & Tracing

The Three Pillars

In a distributed world, simple console logs are not enough. Observability is built on three pillars: **Logs**, **Metrics**, and **Traces**.

Distributed Tracing (OpenTelemetry)

OpenTelemetry (OTel) is the industry standard for tracing requests across multiple services. By passing a trace ID, you can see the lifecycle of a request from the frontend to the database.

// Example: Context propagation in Node.js
import { trace } from '@opentelemetry/api';

const tracer = trace.getTracer('user-service');
const span = tracer.startSpan('db-query');
// ... logic ...
span.end();

Metrics & Alerting

Monitor the health of your services in real-time. Key metrics like CPU usage, error rates, and request latency (p99) allow you to detect problems before they impact users.

Check Your Knowledge

Which pillar allows you to follow a single request across multiple services?

• Tracing
• Logs