Setting up an extension API server to work with the aggregation layer allows the Kubernetes apiserver to be extended with additional APIs, which are not part of the core Kubernetes APIs. Before you begin You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts.

This page provides an overview of admission controllers. An admission controller is a piece of code that intercepts requests to the Kubernetes API server prior to persistence of the resource, but after the request is authenticated and authorized. Several important features of Kubernetes require an admission controller to be enabled in order to properly support the feature. As a result, a Kubernetes API server that is not properly configured with the right set of admission controllers is an incomplete server that will not support all the features you expect.

The Common Expression Language (CEL) is used in the Kubernetes API to declare validation rules, policy rules, and other constraints or conditions. CEL expressions are evaluated directly in the API server, making CEL a convenient alternative to out-of-process mechanisms, such as webhooks, for many extensibility use cases. Your CEL expressions continue to execute so long as the control plane's API server component remains available. Language overview The CEL language has a straightforward syntax that is similar to the expressions in C, C++, Java, JavaScript and Go.

FEATURE STATE: Kubernetes v1.18 [stable] Bootstrap tokens are a simple bearer token that is meant to be used when creating new clusters or joining new nodes to an existing cluster. It was built to support kubeadm, but can be used in other contexts for users that wish to start clusters without kubeadm. It is also built to work, via RBAC policy, with the kubelet TLS Bootstrapping system. Bootstrap Tokens Overview Bootstrap Tokens are defined with a specific type (bootstrap.

A HorizontalPodAutoscaler (HPA for short) automatically updates a workload resource (such as a Deployment or StatefulSet), with the aim of automatically scaling the workload to match demand. Horizontal scaling means that the response to increased load is to deploy more Pods. This is different from vertical scaling, which for Kubernetes would mean assigning more resources (for example: memory or CPU) to the Pods that are already running for the workload.

FEATURE STATE: Kubernetes v1.31 [stable] (enabled by default: true) This document shows you how to use the Pod failure policy, in combination with the default Pod backoff failure policy, to improve the control over the handling of container- or Pod-level failure within a Job. The definition of Pod failure policy may help you to: better utilize the computational resources by avoiding unnecessary Pod retries. avoid Job failures due to Pod disruptions (such preemption, API-initiated eviction or taint-based eviction).

This guide demonstrates how to access the Kubernetes API from within a pod. Before you begin You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:

FEATURE STATE: Kubernetes v1.33 [beta] Kubernetes 1.34 includes optional declarative validation for APIs. When enabled, the Kubernetes API server can use this mechanism rather than the legacy approach that relies on hand-written Go code (validation.go files) to ensure that requests against the API are valid. Kubernetes developers, and people extending the Kubernetes API, can define validation rules directly alongside the API type definitions (types.go files). Code authors define pecial comment tags (e.

Role-based access control (RBAC) is a method of regulating access to computer or network resources based on the roles of individual users within your organization. RBAC authorization uses the rbac.authorization.k8s.io API group to drive authorization decisions, allowing you to dynamically configure policies through the Kubernetes API. To enable RBAC, start the API server with the --authorization-config flag set to a file that includes the RBAC authorizer; for example: apiVersion: apiserver.

In a Kubernetes cluster, the components on the worker nodes - kubelet and kube-proxy - need to communicate with Kubernetes control plane components, specifically kube-apiserver. In order to ensure that communication is kept private, not interfered with, and ensure that each component of the cluster is talking to another trusted component, we strongly recommend using client TLS certificates on nodes. The normal process of bootstrapping these components, especially worker nodes that need certificates so they can communicate safely with kube-apiserver, can be a challenging process as it is often outside of the scope of Kubernetes and requires significant additional work.