For the CKAD exam, the scope of monitoring applications is only within the scope of Kubernetes (including the Kubernetes metrics server). Key metrics to monitor are resources such as CPU and memory along with deployments and their running pods. Labels filter for a specific application or domain during monitoring.
The Kubernetes metrics server is not installed with the Kubernetes installation using kubeadm. Install the Kubernetes metrics-server and learn more about the metrics-server.
With the metrics server installed you can view the resources used reported by the kubelets on each pod with
kubectl top pods:
$ kubectl top pods -n kube-system NAME CPU(cores) MEMORY(bytes) coredns-64897985d-5gn7r 1m 11Mi coredns-64897985d-vbl5w 1m 12Mi etcd-ip-172-31-57-184 15m 43Mi kube-apiserver-ip-172-31-57-184 52m 276Mi kube-controller-manager-ip-172-31-57-184 10m 45Mi kube-proxy-rw4nw 2m 10Mi kube-scheduler-ip-172-31-57-184 3m 17Mi metrics-server-6f7946fdd7-dq6hd 4m 13Mi weave-net-tbhqd 1m 45Mi