What is observability and why is it needed?

Observability is the ability of a system to provide sufficient information about its internal state through external data (logs, metrics, traces) so that one can understand what is happening inside without direct access to the code.

It is needed for quick detection and diagnosis of problems, improving performance and reliability. For example, in a complex C/C++ application with multithreading and hardware interaction, observability helps to understand where bottlenecks or errors occur by analyzing collected metrics and logs.