The Kubernetes API

The Kubernetes API lets you query and manipulate the state of objects in Kubernetes. The core of Kubernetes' control plane is the API server and the HTTP API that it exposes. Users, the different parts of your cluster, and external components all communicate with one another through the API server.

The core of Kubernetes' control plane is the API server. The API server exposes an HTTP API that lets end users, different parts of your cluster, and external components communicate with one another.

The Kubernetes API lets you query and manipulate the state of objects in the Kubernetes API (for example: Pods, Namespaces, ConfigMaps, and Events).

Most operations can be performed through the kubectl command-line interface or other command-line tools, such as kubeadm, which in turn use the API. However, you can also access the API directly using REST calls.

Consider using one of the client libraries if you are writing an application using the Kubernetes API.

OpenAPI specification

Complete API details are documented using OpenAPI.

The Kubernetes API server serves an OpenAPI spec via the /openapi/v2 endpoint. You can request the response format using request headers as follows:

Valid request header values for OpenAPI v2 queries
Header Possible values Notes
Accept-Encoding gzip not supplying this header is also acceptable
Accept application/com.github.proto-openapi.spec.v2@v1.0+protobuf mainly for intra-cluster use
application/json default
* serves application/json

Kubernetes implements an alternative Protobuf based serialization format that is primarily intended for intra-cluster communication. For more information about this format, see the Kubernetes Protobuf serialization design proposal and the Interface Definition Language (IDL) files for each schema located in the Go packages that define the API objects.

API changes

Any system that is successful needs to grow and change as new use cases emerge or existing ones change. Therefore, Kubernetes has designed its features to allow the Kubernetes API to continuously change and grow. The Kubernetes project aims to not break compatibility with existing clients, and to maintain that compatibility for a length of time so that other projects have an opportunity to adapt.

In general, new API resources and new resource fields can be added often and frequently. Elimination of resources or fields requires following the API deprecation policy.

What constitutes a compatible change, and how to change the API, are detailed in API changes.

API groups and versioning

To make it easier to eliminate fields or restructure resource representations, Kubernetes supports multiple API versions, each at a different API path, such as /api/v1 or /apis/rbac.authorization.k8s.io/v1alpha1.

Versioning is done at the API level rather than at the resource or field level to ensure that the API presents a clear, consistent view of system resources and behavior, and to enable controlling access to end-of-life and/or experimental APIs.

To make it easier to evolve and to extend its API, Kubernetes implements API groups that can be enabled or disabled.

API resources are distinguished by their API group, resource type, namespace (for namespaced resources), and name. The API server may serve the same underlying data through multiple API version and handle the conversion between API versions transparently. All these different versions are actually representations of the same resource. For example, suppose there are two versions v1 and v1beta1 for the same resource. An object created by the v1beta1 version can then be read, updated, and deleted by either the v1beta1 or the v1 versions.

Refer to API versions reference for more details on the API version level definitions.

API Extension

The Kubernetes API can be extended in one of two ways:

  1. Custom resources let you declaratively define how the API server should provide your chosen resource API.
  2. You can also extend the Kubernetes API by implementing an aggregation layer.

What's next

Last modified September 21, 2020 at 5:04 PM PST: Clarify what API versions mean (3d416c641)