Add Liveness, Readiness, and Startup Probes Concepts and supply clean up example

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pegasas 2023-08-04 07:32:30 +08:00 committed by Junyao Huang
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title: Liveness, Readiness, and Startup Probes
content_type: concept
weight: 40
---
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Kubernetes has various types of probes:
- [Liveness probe](#liveness-probe)
- [Readiness probe](#readiness-probe)
- [Startup probe](#startup-probe)
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## Liveness probe
Liveness probes determine when to restart a container. For example, liveness probes could catch a deadlock, where an application is running, but unable to make progress.
If a Pod fails health-checks continuously, the Kubernetes terminates the Pod and starts a new one.
Liveness probes do not wait for readiness probes to succeed. If you want to wait before executing a liveness probe you should use initialDelaySeconds or a startupProbe.
## 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](/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes).

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This page shows how to configure liveness, readiness and startup probes for containers.
For more information about probes, see [Liveness, Readiness and Startup Probes](/docs/concepts/configuration/liveness-readiness-startup-probes)
The [kubelet](/docs/reference/command-line-tools-reference/kubelet/) uses
liveness probes to know when to restart a container. For example, liveness
probes could catch a deadlock, where an application is running, but unable to