Metric API Server with k8s

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

It wont work due some certificate issue, for a local cluster i can tell the deployment to ignore using TLS

kubectl edit deploy metrics-server -n kube-system

And add this line to the Args in container spec:

- --kubelet-insecure-tls

apiVersion: apps/v1
kind: Deployment
metadata:
  annotations:
    deployment.kubernetes.io/revision: "2"
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{},"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=4443","--kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname","--kubelet-use-node-status-port","--metric-resolution=15s"],"image":"registry.k8s.io/metrics-server/metrics-server:v0.6.4","imagePullPolicy":"IfNotPresent","livenessProbe":{"failureThreshold":3,"httpGet":{"path":"/livez","port":"https","scheme":"HTTPS"},"periodSeconds":10},"name":"metrics-server","ports":[{"containerPort":4443,"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,"readOnlyRootFilesystem":true,"runAsNonRoot":true,"runAsUser":1000},"volumeMounts":[{"mountPath":"/tmp","name":"tmp-dir"}]}],"nodeSelector":{"kubernetes.io/os":"linux"},"priorityClassName":"system-cluster-critical","serviceAccountName":"metrics-server","volumes":[{"emptyDir":{},"name":"tmp-dir"}]}}}}
  creationTimestamp: "2023-09-12T09:44:33Z"
  generation: 2
  labels:
    k8s-app: metrics-server
  name: metrics-server
  namespace: kube-system
  resourceVersion: "555634"
  uid: b175795b-aaf9-48f6-9cce-a6eec20d30fe
spec:
  progressDeadlineSeconds: 600
  replicas: 1
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      k8s-app: metrics-server
  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 0
    type: RollingUpdate
  template:
    metadata:
      creationTimestamp: null
      labels:
        k8s-app: metrics-server
    spec:
      containers:
      - args:
        - --cert-dir=/tmp
        - --secure-port=4443
        - --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:v0.6.4
...

Create the HorizontalPodAutoscaler

Create a deployment with the it’s service, i will set a CPU limit for this pod, basically it is a web server and i will hammer it with siege utility from another machin client

This is the content of the hpa_examle.yml manifest file

Install siege util: sudo apt install siege

siege http://192.168.1.13:30007

The output of the k top pods command shows that the nignxwebsite pod is currently using 0m CPU, which means it's not being utilized at all. This is a good opportunity to test the HorizontalPodAutoscaler by increasing the load on the server and observing if the number of replicas increases accordingly.

After collecting the metrics, i may take some secondes:

And it exceeds the limit i have set for it

Let’s Configure Autoscaler resource

From the command line utility we can use kbectl to create an autoscale

kubectl autoscale deployment nginxwebsite --cpu-percent=50 --min=1 --max=10

Or using a manifest file:

After using the siege utility to hammer the website

It started creating 3 pods, so the deployment tells the Replicaset spins up extra pods

As you can see the load is

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