Concept / Term · Established
Operational practice
The ability to understand what a system is doing from its telemetry, especially logs, metrics and traces, so unfamiliar failures can be diagnosed.
Field note
Observability is the ability to understand a system’s internal behaviour from the signals it produces. Logs describe events, metrics quantify trends and traces follow a request across components.
The word comes from control theory, where a system is observable when its internal state can be inferred from its outputs. Software operations adopted the idea for complex distributed systems.
Engineers correlate logs, metrics and traces to investigate unfamiliar failures rather than relying only on alerts for problems they predicted in advance.
Modern systems have too many moving parts for a team to diagnose failures by logging into one server and reading one file.
In a sentence“The error rate rose in one region; the trace shows the delay begins at the payment provider.”