k8s - container probes
The liveness, readiness and startup probe are configured per container (not per Pod).
livenessProbe- why?: to know when to restart a container.
- on success: do nothing.
- on failure: restarts the container.
- default behavior: same as success
readinessProbe- why?: to know when a container is ready to accept traffic.
- on success: tells to load balancer the Pod is ready to receive requests.
- on failure: tells to load balancer to not send requests to this Pod.
- default behavior: same as success
startupProbe- why?: to know when a container app has started, and then kubelet can start running the liveness and readiness probes.
- on success: enables liveness and readiness probes.
- on failure: restarts the container
- default behavior: same as success
| probe | liveness | readiness | startup |
|---|---|---|---|
| why? | when to restart a container | when a container is ready to receive traffic | when kubelet can start running liveness/readiness probes |
| when? | after startupProbe and then continuously | after startupProbe and then continuously | after container starts / stops after success or failure |
| success | do nothing | tells the load balancer it's ready to receive traffic | tells kubelet to start running liveness/readiness probes |
| failure | container killed and restarted (see: restartPolicy) | tells load balancer to stop sending traffic | container killed and restarted (see: restartPolicy) |
| default | same as success | same as success | same as success |
diagram with the flow of all probes
