This blog post will show you how to create a built-in health check inside a pod that is running on a Kubernetes cluster.
By default, any Kubernetes cluster maintains a keep-alive process health check that makes sure the pod is running; however, this health check can be deceiving and result in the application not functioning by the pod does.
For that reason, the Kubernetes API comes with a spec that allows us to monitor application inside a running pod.
In the following code, I have a deployment for a Pod that runs a web server, using a liveness check to monitor the health of the webserver.
In code below, I monitor the response from the main web server, and I am checking the status every 5 seconds. If the webserver stops responding and the timeout of 3 seconds is reached, the pod will restart.
apiVersion: v1 kind: Pod metadata: name: mypod spec: containers: - name: mypod image: nginx:latest livenessProbe: httpGet: path: / port: 80 periodSeconds: 5 timeoutSeconds: 3 ports: - containerPort: 80 protocol: TCP
If I debug the pod using the log command I wil see the following output.
[13/Feb/2021:09:15:55 +0000] "GET / HTTP/1.1" 200 612 "-" "kube-probe/1.19" "-" 10. - - [13/Feb/2021:09:16:00 +0000] "GET / HTTP/1.1" 200 612 "-" "kube-probe/1.19" "-" 10. - - [13/Feb/2021:09:16:05 +0000] "GET / HTTP/1.1" 200 612 "-" "kube-probe/1.19" "-"