Some container metrics reported by kubelet are spotty in Grafana dashboards, e.g. https://grafana.wikimedia.org/dashboard/db/kubernetes-pods.
While debugging the issue I tried asking one kubelet every 30s for metrics and indeed not all metrics are reported at every scrape:
while sleep 30; do curl kubernetes1001.eqiad.wmnet:10255/metrics/cadvisor > cadvisor_$(date -Is) ; done
3382 cadvisor_2017-11-28T10:53:51+0000 847 cadvisor_2017-11-28T10:54:22+0000 3382 cadvisor_2017-11-28T10:54:52+0000
The issue ( https://github.com/kubernetes/kubernetes/issues/50151 ) apparently is fixed in k8s 1.8 and 1.7.7 https://github.com/kubernetes/kubernetes/pull/51473#issuecomment-330019449