Metrics Server

• You can have 1 metrics server per Kubernetes cluster
• It retrieves metrics from nodes and pods and stores it in-memory only
• Metrics Server is meant only for autoscaling purposes (Horizontal Pod Autoscaler and Vertical Pod Autoscaler). For example, don't use it to forward metrics to monitoring solutions, or as a source of monitoring solution metrics. In such cases please collect metrics from Kubelet /metrics/resource endpoint directly

# Minikube
minikube addons enable "metrics-server"

# Manifest
kubectl apply -f "https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml"

Kubelet cAdisor

• The kubelet contains a subcomponent cAdvisor
• cAdvisor retrives performance metrics from pods and expose them through the kubelet API endpoint /metrics/resource
• Metrics Server collects resource metrics from these kubelets and exposes them in Kubernetes apiserver through Metrics API

kubectl top

• Metrics Server unlocks the TOP command

# Metrics for all pods/nodes
kubectl top pod --all-namespaces --containers=true
kubectl top node --all-namespaces --containers=true

# Metrics for a specificy pod/node
kubectl top pod "pod-name" --containers
kubectl top node "node-name" --containers