Kubernetes liveness probe

2
votes

How can I write kubernetes readiness probe for my spring boot application, which takes around 20 second to startup ? I tried to follow example from Configure Liveness, Readiness and Startup Probes, but I'm not sure how does Kubernetes figure out status code 200 as success 

apiVersion: v1
kind: Pod
metadata:
  labels:
    app: backend
    name: liveness-http
spec:
  containers:
  - name: liveness
    image: k8s.gcr.io/liveness
    args:
    - /server
    livenessProbe:
      httpGet:
        path: /healthz
        port: 8080
        httpHeaders:
        - name: Custom-Header
          value: Awesome
      initialDelaySeconds: 3
      periodSeconds: 3
3
kubernetesgoogle-kubernetes-engine

3 Answers

3
votes

Kubernetes kubelet will make a http request at /healthz path in your application and expects http status code 200 returned from that endpoint for the probe to be successful. So you need to have a rest endpoint in a rest controller which will return 200 from /healthz. An easy way to achieve it would be to include spring boot actuator dependency and change the liveness probe path to /actuator/health/liveness. Spring boot actuator by default comes with a rest controller endpoint which returns 200 from /actuator/health/liveness.

https://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-features.html#production-ready-kubernetes-probes

2
votes

initialDelaySeconds field tells the kubelet that it should wait 20 seconds before performing the first probe. So this is generally configured to the value/time that the container / pod takes to start.

Configure initialDelaySeconds: 20 with the value as 20 seconds.

0
votes

K8 engine considers response code 200-399 as a successful probe. In your case you can add initial delay seconds for your probe to start with a delay of 20 seconds.