Observability

Definition

Observability is a measure of how well internal states of a system can be inferred from knowledge of its external outputs. In software, it refers to the ability to understand what is happening inside a complex system just by observing its outputs, such as logs, metrics, and traces.

Why It Matters

In modern distributed systems like microservices, it's no longer possible to debug by logging into a single server. Observability provides the tools and practices needed to understand and troubleshoot these complex systems by collecting and analyzing telemetry data.

Contextual Example

A developer is investigating why some user requests are slow. They use a distributed tracing tool to view a trace, which shows the entire lifecycle of a request as it travels through multiple microservices. They can see exactly which service is causing the delay.

Common Misunderstandings

• The "three pillars of observability" are logs (records of discrete events), metrics (a numeric representation of data measured over time), and traces (a representation of a single request's journey through the system).
• Observability is more than just monitoring. Monitoring tells you *that* something is wrong; observability lets you ask questions to figure out *why*.