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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 start accepting traffic. This is useful when waiting for an application to perform time-consuming initial tasks, such as establishing network connections, loading files, and warming caches.
If the readiness probe returns a failed state, Kubernetes removes the pod from all matching service endpoints.
Readiness probes runs 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 readiness probes, which are run periodically.
- Read more about the Configure Liveness, Readiness and Startup Probes.