What is the source of kubernetes.pod.memory.usage.bytes and kubernetes.pod.cpu.usage.nanocores metrics?

I am wondering where the metrics kubernetes.pod.memory.usage.bytes and kubernetes.pod.cpu.usage.nanocores in metricbeat are obtained from? Are they OS statistics? If so, which statistic? I am trying to compare them against kubectl top

I believe these metrics are from stats/summary endpoint based on the code: beats/pod.go at master · elastic/beats · GitHub

@ChrsMark Please correct me if I'm wrong here. TIA!

That's correct. These are metrics collected from kubelet's endpoint Kaiyan provided above.

@ChrsMark , @Kaiyan_Sheng

So, from that it looks like both metricbeat and kubectl top use the same source:

Kubectl top uses Metrics Server