Kubernetes comes built in with some basic instrumentation to know how much CPU and memory are consumed on each node in the cluster. Exactly what is captured and how it is captured has been evolving rapidly in recent Kubernetes releases (1.5 through 1.9). Many Kubernetes installations will be capturing information about what resources the underlying containers are using with a program called cAdvisor. This code was created by Google to collect, aggregate, and expose the metrics of how containers are operating, as a critical step of being able to know where best to place new containers, based on what resources a node has and where resources are available.
Every node within a Kubernetes cluster will have cAdvisor running and collecting information, and this, in turn, is captured and used by kubelet, which is the local agent on every node that is responsible for starting, stopping, and managing the various resources needed to run containers.
cAdvisor exposes a...
