Observability

Logging

Create a busybox pod that 'echo Hello World!'. Show the logs of the pod:

kubectl run busybox --image=busybox --restart=Never -- /bin/sh -c 'echo Hello World!'
kubectl logs busybox

Liveness probes

Create nginx pod and add HTTP GET liveness probe that hit '/' after 10 seconds of initializing the pod

kubectl explain pod.spec.containers.livenessProbe
kubectl explain pod.spec.containers.livenessProbe.httpGet
kubectl run nginx --image=nginx --restart=Never -o yaml --dry-run > pod.yaml

# Edit pod.yaml and add liveness probe
  livenessProbe:
    initialDelaySeconds: 10
    httpGet:
      path: /
      port: 80
   

Readiness probes

Unlike liveness probes, if a container fails the readiness check, it won’t be killed or restarted. It is a way to tell kubernetes that I'm the container not yet "ready" receive requests.

kubectl explain pod.spec.containers.readinessProbe
kubectl explain pod.spec.containers.readinessProbe.exec
kubectl run nginx --image=nginx --restart=Never -o yaml --dry-run > pod.yaml

# Edit pod.yaml and add liveness probe
  readinessProbe:
    exec:
      command:
        - cat
        - /etc/passwd

kubectl describe po nginx | grep Read 

Change the command in the previous pod to not existent file and describe the pod. Check the events and logs

kubectl logs nginx
kubectl describe po nginx 
kubectl describe po nginx | grep Read
# Ready: False and ContainersReady: False