Solve error: Metrics API not available

Install metrics-server

• Using remote file

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

• Or using local file

apiVersion: v1
kind: ServiceAccount
metadata:
  labels:
    k8s-app: metrics-server
  name: metrics-server
  namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  labels:
    k8s-app: metrics-server
    rbac.authorization.k8s.io/aggregate-to-admin: 'true'
    rbac.authorization.k8s.io/aggregate-to-edit: 'true'
    rbac.authorization.k8s.io/aggregate-to-view: 'true'
  name: system:aggregated-metrics-reader
rules:
  - apiGroups:
      - metrics.k8s.io
    resources:
      - pods
      - nodes
    verbs:
      - get
      - list
      - watch
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  labels:
    k8s-app: metrics-server
  name: system:metrics-server
rules:
  - apiGroups:
      - ''
    resources:
      - nodes/metrics
    verbs:
      - get
  - apiGroups:
      - ''
    resources:
      - pods
      - nodes
    verbs:
      - get
      - list
      - watch
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  labels:
    k8s-app: metrics-server
  name: metrics-server-auth-reader
  namespace: kube-system
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: extension-apiserver-authentication-reader
subjects:
  - kind: ServiceAccount
    name: metrics-server
    namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  labels:
    k8s-app: metrics-server
  name: metrics-server:system:auth-delegator
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: system:auth-delegator
subjects:
  - kind: ServiceAccount
    name: metrics-server
    namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  labels:
    k8s-app: metrics-server
  name: system:metrics-server
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: system:metrics-server
subjects:
  - kind: ServiceAccount
    name: metrics-server
    namespace: kube-system
---
apiVersion: v1
kind: Service
metadata:
  labels:
    k8s-app: metrics-server
  name: metrics-server
  namespace: kube-system
spec:
  ports:
    - name: https
      port: 443
      protocol: TCP
      targetPort: https
  selector:
    k8s-app: metrics-server
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    k8s-app: metrics-server
  name: metrics-server
  namespace: kube-system
spec:
  selector:
    matchLabels:
      k8s-app: metrics-server
  strategy:
    rollingUpdate:
      maxUnavailable: 0
  template:
    metadata:
      labels:
        k8s-app: metrics-server
    spec:
      containers:
        - args:
            - --cert-dir=/tmp
            - --secure-port=10250
            - --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname
            - --kubelet-use-node-status-port
            - --metric-resolution=15s
          image: registry.k8s.io/metrics-server/metrics-server:v0.7.1
          imagePullPolicy: IfNotPresent
          livenessProbe:
            failureThreshold: 3
            httpGet:
              path: /livez
              port: https
              scheme: HTTPS
            periodSeconds: 10
          name: metrics-server
          ports:
            - containerPort: 10250
              name: https
              protocol: TCP
          readinessProbe:
            failureThreshold: 3
            httpGet:
              path: /readyz
              port: https
              scheme: HTTPS
            initialDelaySeconds: 20
            periodSeconds: 10
          resources:
            requests:
              cpu: 100m
              memory: 200Mi
          securityContext:
            allowPrivilegeEscalation: false
            capabilities:
              drop:
                - ALL
            readOnlyRootFilesystem: true
            runAsNonRoot: true
            runAsUser: 1000
            seccompProfile:
              type: RuntimeDefault
          volumeMounts:
            - mountPath: /tmp
              name: tmp-dir
      nodeSelector:
        kubernetes.io/os: linux
      priorityClassName: system-cluster-critical
      serviceAccountName: metrics-server
      volumes:
        - emptyDir: {}
          name: tmp-dir
---
apiVersion: apiregistration.k8s.io/v1
kind: APIService
metadata:
  labels:
    k8s-app: metrics-server
  name: v1beta1.metrics.k8s.io
spec:
  group: metrics.k8s.io
  groupPriorityMinimum: 100
  insecureSkipTLSVerify: true
  service:
    name: metrics-server
    namespace: kube-system
  version: v1beta1
  versionPriority: 100

Issue

When I run kubectl top nodes or kubectl top pods, I got the error: error: Metrics API not available

I get the log of the pod:

kubectl logs metrics-server-7ffbc6d68-q5qt2 -n kube-system

E0729 14:55:56.535369       1 scraper.go:149] "Failed to scrape node" err="Get \"https://10.222.1.37:10250/metrics/resource\": tls: failed to verify certificate: x509: cannot validate certificate for 10.222.1.37 because it doesn't contain any IP SANs" node="ubuntu-1"
E0729 14:55:56.547265       1 scraper.go:149] "Failed to scrape node" err="Get \"https://10.222.1.171:10250/metrics/resource\": tls: failed to verify certificate: x509: cannot validate certificate for 10.222.1.171 because it doesn't contain any IP SANs" node="ubuntu-2"
I0729 14:55:59.709600       1 server.go:191] "Failed probe" probe="metric-storage-ready" err="no metrics to serve"
I0729 14:56:09.710182       1 server.go:191] "Failed probe" probe="metric-storage-ready" err="no metrics to serve"

Solution

Kubernetes API using self-signed certificates, so we need to add --kubelet-insecure-tls to the metrics-server deployment.

kubectl patch deployment metrics-server -n kube-system --type='json' -p='[{"op": "add", "path": "/spec/template/spec/containers/0/args/-", "value": "--kubelet-insecure-tls"}]'