Liveness, readiness and startup probes

Kubernetes · lesson 10 of 32 · 4 min read

Tell Kubernetes when your container can take traffic, when it must be restarted, and how long to wait at boot.

Key points

readiness controls traffic. Fail it and the pod leaves the Service endpoints, but it is not restarted.
liveness controls restarts. Fail it and the kubelet kills the container. Keep this check dumb and local.
Never touch the database from a liveness probe. One slow query then restarts every pod at once.
startup probes cover slow boots. While one runs, the other two are paused, which beats a huge initialDelaySeconds.
Spring Boot serves /actuator/health/liveness and /actuator/health/readiness, enabled automatically when it detects Kubernetes.

Example

containers:
  - name: app
    image: ghcr.io/acme/web:1.4.2
    ports:
      - containerPort: 8080
    startupProbe:              # up to 30 x 5s = 150s to boot
      httpGet:
        path: /actuator/health/liveness
        port: 8080
      failureThreshold: 30
      periodSeconds: 5
    readinessProbe:
      httpGet:
        path: /actuator/health/readiness
        port: 8080
      periodSeconds: 5
      failureThreshold: 3
    livenessProbe:
      httpGet:
        path: /actuator/health/liveness
        port: 8080
      periodSeconds: 10
      failureThreshold: 3

Readiness protects your users. Liveness protects you from a wedged process.

This is a reading copy. The full lesson — with the visual explainer, the interactive lab and a Run button for the code — lives in the Kubernetes course, and every lesson in it is listed on the Kubernetes contents page.