Kubernetes: LivenessProbes - first check

One key feature of kubernetes is, that unhealthy pods will be restarted. How can this be tested?

First you should deploy KUARD (kubernetes up and runnind demo). With this docker image you can check the restart feature easily:

(To deploy kuard read this posting, but there a some small differences)

# kubectl create namespace kuard
namespace/kuard created

But then you can not use the kubectl run because there is no commandline parameter to add the livenessProbe configuration. So you have to write a yaml file:

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: kuard
  name: kuard
  namespace: kuard
spec:
  containers:
  - image: gcr.io/kuar-demo/kuard-arm64:3
    name: kuard
    livenessProbe:
      httpGet:
        path: /healthy
        port: 8080
      initialDelaySeconds: 5
      timeoutSeconds: 1
      periodSeconds: 10
      failureThreshold: 3
    ports:
    - containerPort: 8080
    resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}

and then run

# kubectl apply -f kuard.yaml -n kuard

The exposed port will stay (this posting) untouched, so you can reach your kuard over http.

So go to the tab "liveness probe" and you will see:

Now click on "Fail" and the livenessProbe will get a http 500:

 And after 3 retries you will see:

and the command line will show 1 restart:

# kubectl get all -n kuard
NAME        READY   STATUS    RESTARTS   AGE
pod/kuard   1/1     Running   1          118s

NAME            TYPE       CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
service/kuard   NodePort   10.152.183.227   <none>        8080:32047/TCP   3d21h

Really cool - but really annoying, that this could not be configured via CLI but only per YAML.