package apiserver

import "k8s.io/apiserver"

Package apiserver provides the machinery for building Kubernetes-style API servers.

This library is the foundation for the Kubernetes API server (`kube-apiserver`), and is also the primary framework for developers building custom API servers to extend the Kubernetes API.

An extension API server is a user-provided, standalone web server that registers itself with the main kube-apiserver to handle specific API groups. This allows developers to extend Kubernetes with their own APIs that behave like core Kubernetes APIs, complete with typed clients, authentication, authorization, and discovery.

Key Packages

The `apiserver` library is composed of several key packages:

• `pkg/server`: This is the core of the library, providing the `GenericAPIServer` and the main machinery for building the server.
• `pkg/admission`: This package contains the admission control framework. Developers can use this to build custom admission plugins that can validate or mutate requests to enforce custom policies. This is a common way to extend Kubernetes behavior without adding a full API server.
• `pkg/authentication`: This package provides the framework for authenticating requests.
• `pkg/authorization`: This package provides the framework for authorizing requests.
• `pkg/endpoints`: This package contains the machinery for building the REST endpoints for the API server.
• `pkg/registry`: This package provides the storage interface for the API server.

Instantiating a GenericAPIServer

The `GenericAPIServer` struct is the heart of any extension server. It is responsible for assembling and running the HTTP serving stack. See the runnable example for a demonstration of how to instantiate a `GenericAPIServer`.

Building an Extension API Server (API Aggregation)

The mechanism that enables extension API servers is API aggregation. The primary apiserver (typically the kube-apiserver) acts as a proxy, forwarding requests for a specific API group (e.g., /apis/myextension.io/v1) to a registered extension server. The apiserver is configured using APIService objects.

For most use cases, custom resources (CustomResourceDefinitions) are the preferred way to extend the Kubernetes API.

Building an Admission Plugin

The `pkg/admission` package provides a way to add admission policies directly into an apiserver. Admission plugins can be used to validate or mutate objects during write operations. The kube-apiserver uses admission plugins to provide a variety of core system capabilities.

For most extension use cases dynamic admission control using policies (ValidatingAdmissionPolicies or MutatingAdmissionPolicies) or webhooks (ValidatingWebhookConfiguration and MutatingWebhookConfiguration) are the preferred way to extend admission control.

Index ¶

Source Files ¶

doc.go

Directories ¶