Kubelet API Server Connectivity Test

The Kubelet is an agent that runs on each node in the Kubernetes cluster. It ensures that containers are running in a Pod by communicating with the Kubernetes API Server to get the desired state of the Pods and then ensuring that the containers match that state. It monitors the state of containers and nodes, handles container logs, and manages the node's resources. For performing its function Kubelet requires uninterrupted connectivity with API Server. That's the reason it si important to monitor the API Server connectivity for Kubelet so that any potential issue with connectivity can be identified beforehand.

This test monitors the Kubelet API Server connectivity and reveal key metrics which are crucial to maintaining the connectivity like certificate status, number of requests, latency etc. Administrators can analyze these metrics over time to get valuable insights into current state and potential issues which can cause connectivity to fail.

Target of the test : A Kubernetes Worker Node

Agent deploying the test : A remote agent

Outputs of the test : One set of results for target Kubernetes Worker node being monitored.

Configurable parameters for the test

Parameter	Description
Test Period	How often should the test be executed.
Host	The IP address of the host for which this test is to be configured.
Port	Specify the port at which the specified Host listens. By default, this is 6443.
Timeout	Specify the duration (in seconds) beyond which the test will timeout in the Timeout text box. The default value is 10 seconds.
Metric URL	Each of the Kubernetes system components expose monitoring metrics through /metrics endpoint of the HTTP server. For components that don't expose endpoint by default, refer official Kubernetes distribution documentation site. Specify the metric URL textbox.

Measurements made by the test

Measurement	Description	Measurement Unit	Interpretation
Number of certificate remaining lifetime	Indicates the number of certificates having remaining lifetime.	Number	If there are any certificates for which the lifetime is less, they can give problem very soon.
Total certificate remaining lifetime	Indicates the total lifetime of all certificates.	Number	If the total remaining lifetime is below threshold, administrators need to get the certificates re-validated.
Total request latency	Indicates the latency of the request from Kubelet and API server.	Milliseconds	Request latency should be within the threshold limits, if it is beyod that, it will have to be investigated.
Number of request latency	Indicates the number of requests where time taken for request was more then latency threshold.	Number
Average certificate remaining lifetime	Indicates the average remaining lifetime per certificate.	Number	If the average remaining lifetime is below threshold, administrators need to get the certificates re-validated.
Average request latency	Indicates the average latency of the requests from Kubelet to API server.	Milliseconds	Request latency should be within the threshold limits, if it is beyod that, it will have to be investigated.