Overview

The kubelet command-line has 177 parameters, making it the Kubernetes component with the most configuration options.

Kubelet’s options can be categorized into three types: kubeletFlags (those that cannot be changed after startup and can only be configured via the command line, such as IP addresses and paths), kubeletConfiguration (those that can be modified after startup and can be set via the command line, configuration files, or dynamic Kubelet config - configmap; configuring via the command line is deprecated, and some options can only be set through configuration files, e.g., NodeStatusReportFrequency), and globalFlags (those that can only be configured via the command line, such as log levels, log paths, and versions).

The Taint Manager is triggered by pod and node events. It examines whether nodes bound to pods or nodes themselves have a “NoExecute” taint. If such taints are present, the Taint Manager proceeds to delete all pods on the affected node(s) or a specific pod.

In the previous article about the Node Lifecycle Controller, if the Taint Manager is enabled, it is initialized using NewNoExecuteTaintManager.

Within the Node Lifecycle Controller, handlers are defined for pod and node events. When the Taint Manager is enabled, these events are added to the nodeUpdateQueue and podUpdateQueue within the Taint Manager.

Additionally, a goroutine is launched in the Node Lifecycle Controller to execute taintManager.Run(stopCh).

The Node Lifecycle Controller Manager decides whether to evict pods on a node or set taints based on node leases and node status update times. It also sets the node ready condition to “unknown” when needed. Additionally, it adjusts the node eviction rate based on the overall cluster state and the number of unready nodes in a zone, enabling it to add taints or execute pod evictions as necessary.