This page explains how to add versioning information to CustomResourceDefinitions, to indicate the stability level of your CustomResourceDefinitions. It also describes how to upgrade an object from one version to another.
Note: All specified versions must use the same schema. The is no schema conversion between versions.
You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using Minikube, or you can use one of these Kubernetes playgrounds:
To check the version, enter
Make sure your Kubernetes cluster has a master version of 1.11.0 or higher.
Read about custom resources.
The CustomResourceDefinition API supports a
versions field that you can use to
support multiple versions of custom resources that you have developed, and
indicate the stability of a given custom resource. All versions must currently
use the same schema, so if you need to add a field, you must add it to all
Earlier iterations included a
versionfield instead of
versionfield is deprecated and optional, but if it is not empty, it must match the first item in the
This example shows a CustomResourceDefinition with two versions. The comments in the YAML provide more context.
apiVersion: apiextensions.k8s.io/v1beta1 kind: CustomResourceDefinition metadata: # name must match the spec fields below, and be in the form: <plural>.<group> name: crontabs.example.com spec: # group name to use for REST API: /apis/<group>/<version> group: example.com # list of versions supported by this CustomResourceDefinition versions: - name: v1beta1 # Each version can be enabled/disabled by Served flag. served: true # One and only one version must be marked as the storage version. storage: true - name: v1 served: true storage: false # either Namespaced or Cluster scope: Namespaced names: # plural name to be used in the URL: /apis/<group>/<version>/<plural> plural: crontabs # singular name to be used as an alias on the CLI and for display singular: crontab # kind is normally the CamelCased singular type. Your resource manifests use this. kind: CronTab # shortNames allow shorter string to match your resource on the CLI shortNames: - ct
You can save the CustomResourceDefinition in a YAML file, then use
kubectl create to create it.
kubectl create -f my-versioned-crontab.yaml
After creation, the API server starts to serve each enabled version at an HTTP
REST endpoint. In the above example, the API versions are available at
Regardless of the order in which versions are defined in a CustomResourceDefinition, the version with the highest priority is used by kubectl as the default version to access objects. The priority is determined by parsing the name field to determine the version number, the stability (GA, Beta, or Alpha), and the sequence within that stability level.
The algorithm used for sorting the versions is designed to sort versions in the
same way that the Kubernetes project sorts Kubernetes versions. Versions start with a
v followed by a number, an optional
alpha designation, and
optional additional numeric versioning information. Broadly, a version string might look
v2beta1. Versions are sorted using the following algorithm:
alphafollow the first numeric portion, they sorted in that order, after the equivalent string without the
alphasuffix (which is presumed to be the GA version).
alpha, those numbers are also sorted from largest to smallest.
foo1is sorted above
foo10. This is different from the sorting of the numeric portion of entries that do follow the Kubernetes version patterns.
This might make sense if you look at the following sorted version list:
- v10 - v2 - v1 - v11beta2 - v10beta3 - v3beta1 - v12alpha1 - v11alpha2 - foo1 - foo10
For the example in Specify multiple versions, the
version sort order is
v1, followed by
v1beta1. This causes the kubectl
command to use
v1 as the default version unless the provided object specifies
When an object is written, it is persisted at the version designated as the storage version at the time of the write. If the storage version changes, existing objects are never converted automatically. However, newly-created or updated objects are written at the new storage version. It is possible for an object to have been written at a version that is no longer served.
When you read an object, you specify the version as part of the path. If you
specify a version that is different from the object’s persisted version,
Kubernetes returns the object to you at the version you requested, but the
persisted object is neither changed on disk, nor converted in any way
(other than changing the
apiVersion string) while serving the request.
You can request an object at any version that is currently served.
If you update an existing object, it is rewritten at the version that is currently the storage version. This is the only way that objects can change from one version to another.
To illustrate this, consider the following hypothetical series of events:
v1beta1. You create an object. It is persisted in storage at version
v1to your CustomResourceDefinition and designate it as the storage version.
v1beta1, then you read the object again at version
v1. Both returned objects are identical except for the apiVersion field.
v1. You now have two objects, one of which is at
v1beta1, and the other of which is at
v1since that is the current storage version.
The API server records each version which has ever been marked as the storage
version in the status field
storedVersions. Objects may have been persisted
at any version that has ever been designated as a storage version. No objects
can exist in storage at a version that has never been a storage version.
When deprecating versions and dropping support, devise a storage upgrade
procedure. The following is an example procedure to upgrade from
v1as the storage in the CustomResourceDefinition file and apply it using kubectl. The