The Three Pillars — Logs, Metrics, and Traces
Understand the three pillars of observability — what each tells you, how they complement each other, and how OpenTelemetry unifies them.
Your app is in production. Users are using it. And then something goes wrong. Page loads take 8 seconds. An API returns 500 errors intermittently. A feature that worked yesterday silently breaks.
How do you figure out what happened?
If your answer is "add some console.log statements and redeploy," you're flying blind. That's like a doctor diagnosing a patient by asking them to come back tomorrow after swallowing a thermometer.
Observability is the practice of understanding what's happening inside your system by examining its outputs. It rests on three pillars — logs, metrics, and traces — and each tells you something different. Together, they give you the full picture.
Pillar 1: Logs — What Happened
Logs are timestamped records of discrete events. They answer **wha
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