cAdvisor (Google)

cAdvisor, short for Container Advisor, is a daemon from Google that collects, aggregates, processes and exports information about running containers, giving users an understanding of resource usage and performance. For each container it keeps resource isolation parameters, historical resource usage and histograms of that usage over time.

Its significance comes from where it sits rather than from what it presents. cAdvisor is the component that actually reads container resource statistics from the kernel, and the dashboards an operator looks at are usually displaying numbers that originated here, which makes it infrastructure almost nobody chooses deliberately.

Keeping histograms rather than only current values is the design detail that matters for diagnosis. Knowing that a container is using two gigabytes now answers little, while knowing how its usage was distributed over the last hour distinguishes a steady workload from one that spikes and is about to be killed.

What it is not is a monitoring product. There is no alerting, retention or multi-cluster view here, so it is a source of data for something else rather than the thing an operator opens when something breaks. Knowing that is what prevents a team from expecting it to replace a monitoring platform.