Liveness, Readiness, and Startup Probes
Kubernetes has various types of probes:
Liveness probe
Liveness probes determine when to restart a container. For example, liveness probes could catch a deadlock when an application is running but unable to make progress.
If a container fails its liveness probe repeatedly, the kubelet restarts the container.
Liveness probes do not wait for readiness probes to succeed. If you want to wait before executing a liveness probe, you can either define initialDelaySeconds or use a
startup probe.
Readiness probe
Readiness probes determine when a container is ready to accept traffic. This is useful when waiting for an application to perform time-consuming initial tasks that depend on its backing services; for example: establishing network connections, loading files, and warming caches. Readiness probes can also be useful later in the container’s lifecycle, for example, when recovering from temporary faults or overloads.
If the readiness probe returns a failed state, Kubernetes removes the pod from all matching service endpoints.
Readiness probes run on the container during its whole lifecycle.
Startup probe
A startup probe verifies whether the application within a container is started. This can be used to adopt liveness checks on slow starting containers, avoiding them getting killed by the kubelet before they are up and running.
If such a probe is configured, it disables liveness and readiness checks until it succeeds.
This type of probe is only executed at startup, unlike liveness and readiness probes, which are run periodically.
- Read more about the Configure Liveness, Readiness and Startup Probes.