Install metric server on controller node
See https://github.com/kubernetes-sigs/metrics-server/releases https://github.com/kubernetes-sigs/metrics-server to download compactible versions
Obtain metric server YAML 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:
- appProtocol: https
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:
replicas: 2
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
- --kubelet-insecure-tls
image: registry.k8s.io/metrics-server/metrics-server:v0.8.0
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
Apply metric YAML on controller
kubectl apply -f metric.yaml
Verify to see if metrics-server pod is running
kubectl get pods -n kube-system
NAME READY STATUS RESTARTS AGE
calico-kube-controllers-79949b87d-9qddx 1/1 Running 2 (24h ago) 5d23h
calico-node-2l24s 1/1 Running 2 (24h ago) 5d23h
calico-node-f5jxk 1/1 Running 3 (24h ago) 5d23h
calico-node-f9ztb 1/1 Running 1 (24h ago) 5d23h
calico-node-gpxxw 1/1 Running 1 (24h ago) 5d23h
coredns-674b8bbfcf-5zxmv 1/1 Running 1 (24h ago) 5d23h
coredns-674b8bbfcf-7f5wg 1/1 Running 1 (24h ago) 5d23h
etcd-kubnew-master01 1/1 Running 2 (24h ago) 5d23h
etcd-kubnew-master02 1/1 Running 1 (24h ago) 5d23h
kube-apiserver-kubnew-master01 1/1 Running 2 (24h ago) 5d23h
kube-apiserver-kubnew-master02 1/1 Running 2 (24h ago) 5d23h
kube-controller-manager-kubnew-master01 1/1 Running 2 (24h ago) 5d23h
kube-controller-manager-kubnew-master02 1/1 Running 1 (24h ago) 5d23h
kube-proxy-9xvl5 1/1 Running 1 (24h ago) 5d23h
kube-proxy-lfm8f 1/1 Running 2 (24h ago) 5d23h
kube-proxy-mpvsl 1/1 Running 3 (24h ago) 5d23h
kube-proxy-vpknq 1/1 Running 1 (24h ago) 5d23h
kube-scheduler-kubnew-master01 1/1 Running 2 (24h ago) 5d23h
kube-scheduler-kubnew-master02 1/1 Running 1 (24h ago) 5d23h
metrics-server-56fb9549f4-8vqdf 1/1 Running 0 44m
metrics-server-56fb9549f4-m9rsn 1/1 Running 0 44m
Note pod replia count before scaling
kubectl get pods
NAME READY STATUS RESTARTS AGE
mysql-colt-database-5bc5d55fc-gcxpg 1/1 Running 0 6s
mysql-colt-database-5bc5d55fc-lgvth 1/1 Running 0 6s
nginx-test-b548755db-jskkl 1/1 Running 2 (6m44s ago) 4d21h
Apply horizontal scaling to mysql database pod
Create following YAML mentioning min, max replicas, CPU, memory benchmarks
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
name: mysql-colt-scaler
spec:
scaleTargetRef:
apiVersion: apps/v1
kind: Deployment # statefulset, replicaset
name: mysql-colt-database
minReplicas: 3
maxReplicas: 10
metrics:
- type: Resource # Pods, Object, External
resource:
name: cpu # cpu or memory
target:
type: Utilization
averageUtilization: 60
- type: Resource # Pods, Object, External
resource:
name: memory # cpu or memory
target:
type: Utilization
averageUtilization: 30
Appy it on controller
kubectl apply -f scaling.yaml
Verify added horizontal scale “mysql-colt-scaler”
kubectl get horizontalpodautoscalers.autoscaling mysql-colt-scaler
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
mysql-colt-scaler Deployment/mysql-colt-database cpu: 0%/60%, memory: 74%/30% 3 10 10 21m
Check Scaling events
kubectl get horizontalpodautoscalers mysql-colt-scaler
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
mysql-colt-scaler Deployment/mysql-colt-database cpu: 0%/60%, memory: 74%/30% 3 10 10 30m
kubuser@kubnew-master01:~/apps$ kubectl get horizontalpodautoscalers mysql-colt-scaler
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
mysql-colt-scaler Deployment/mysql-colt-database cpu: 0%/60%, memory: 74%/30% 3 10 10 30m
kubuser@kubnew-master01:~/apps$ kubectl get horizontalpodautoscalers mysql-colt-scaler -o wide
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
mysql-colt-scaler Deployment/mysql-colt-database cpu: 0%/60%, memory: 74%/30% 3 10 10 30m
kubuser@kubnew-master01:~/apps$ kubectl describe horizontalpodautoscalers mysql-colt-scaler
Name: mysql-colt-scaler
Namespace: default
Labels: <none>
Annotations: <none>
CreationTimestamp: Tue, 18 Nov 2025 10:26:42 +0530
Reference: Deployment/mysql-colt-database
Metrics: ( current / target )
resource cpu on pods (as a percentage of request): 0% (5m) / 60%
resource memory on pods (as a percentage of request): 74% (389166284800m) / 30%
Min replicas: 3
Max replicas: 10
Deployment pods: 10 current / 10 desired
Conditions:
Type Status Reason Message
---- ------ ------ -------
AbleToScale True ReadyForNewScale recommended size matches current size
ScalingActive True ValidMetricFound the HPA was able to successfully calculate a replica count from memory resource utilization (percentage of request)
ScalingLimited True TooManyReplicas the desired replica count is more than the maximum replica count
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulRescale 30m horizontal-pod-autoscaler New size: 3; reason: Current number of replicas below Spec.MinReplicas
Normal SuccessfulRescale 30m horizontal-pod-autoscaler New size: 5; reason: memory resource utilization (percentage of request) above target
Normal SuccessfulRescale 30m horizontal-pod-autoscaler New size: 7; reason: memory resource utilization (percentage of request) above target
Normal SuccessfulRescale 30m horizontal-pod-autoscaler New size: 10; reason: memory resource utilization (percentage of request) above target
Check newly spawned up pods
kubuser@kubnew-master01:~/apps$ kubectl get pods
NAME READY STATUS RESTARTS AGE
mysql-colt-database-5bc5d55fc-685lv 1/1 Running 0 31m
mysql-colt-database-5bc5d55fc-9dsk8 1/1 Running 1 (4m29s ago) 31m
mysql-colt-database-5bc5d55fc-bsjm7 1/1 Running 1 (4m34s ago) 31m
mysql-colt-database-5bc5d55fc-c5hzf 1/1 Running 0 31m
mysql-colt-database-5bc5d55fc-ft5hb 1/1 Running 0 31m
mysql-colt-database-5bc5d55fc-glh4r 1/1 Running 1 (4m34s ago) 33m
mysql-colt-database-5bc5d55fc-kz694 1/1 Running 0 31m
mysql-colt-database-5bc5d55fc-p7brg 1/1 Running 1 (4m29s ago) 31m
mysql-colt-database-5bc5d55fc-qntnb 1/1 Running 1 (4m29s ago) 33m
mysql-colt-database-5bc5d55fc-zc2v8 1/1 Running 1 (4m34s ago) 32m
nginx-test-b548755db-jskkl 1/1 Running 2 (4m29s ago) 4d21h
kubuser@kubnew-master01:~/apps$
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