How to check Containers health inside a kubernetes pod using livenessProbe?

A Probe is a diagnostic performed periodically by the kubelet on a Container. To perform a diagnostic, the kubelet calls a Handler implemented by the Container. There are three types of handlers:

  • ExecAction: Executes a specified command inside the Container. The diagnostic is considered successful if the command exits with a status code of 0.
  • TCPSocketAction: Performs a TCP check against the Container’s IP address on a specified port. The diagnostic is considered successful if the port is open.
  • HTTPGetAction: Performs an HTTP Get request against the Container’s IP address on a specified port and path. The diagnostic is considered successful if the response has a status code greater than or equal to 200 and less than 400.

Each probe has one of three results:

  • Success: The Container passed the diagnostic.
  • Failure: The Container failed the diagnostic.
  • Unknown: The diagnostic failed, so no action should be taken.

The kubelet can perform and react to two kinds of probes on running Containers:

  • livenessProbe: Indicates whether the Container is running. If the liveness probe fails, the kubelet kills the Container, and the Container is subjected to its restart policy. If a Container does not provide a liveness probe, the default state is Success.
  • readinessProbe: Indicates whether the Container is ready to service requests. If the readiness probe fails, the endpoints controller removes the Pod’s IP address from the endpoints of all Services that match the Pod. The default state of readiness before the initial delay is Failure. If a Container does not provide a readiness probe, the default state is Success.

In this excercise, I would like to discuss on livenessProbe.

Here is the example for livenessProbe using ExecAction

Here is the example for livenessProbe using TCPSocketAction

Here is the example for livenessProbe using HTTPGetAction