Netdata

Netdata is an agent based monitoring system that samples metrics from hosts, containers, and applications every second and streams them to a live dashboard. It covers CPU, memory, disks, network, and processes, adds application metrics from integrations such as Nginx, Postgres, and Docker, and includes statistical anomaly detection that highlights unusual behaviour before fixed thresholds are crossed.

Operators use it to spot a leaking container or a runaway process the moment it happens.

Deploying it on your own infrastructure keeps fine-grained telemetry off third-party platforms, involves no cost per host or metric, and stores history in a database you own and can back up.