--- title: Versions of CustomResourceDefinitions reviewers: - mbohlool - sttts - liggitt content_template: templates/task weight: 30 --- {{% capture overview %}} This page explains how to add versioning information to [CustomResourceDefinitions](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#customresourcedefinition-v1beta1-apiextensions), to indicate the stability level of your CustomResourceDefinitions. It also describes how to upgrade an object from one version to another. {{< note >}} **Note**: All specified versions must use the same schema. The is no schema conversion between versions. {{< /note >}} {{% /capture %}} {{% capture prerequisites %}} {{< include "task-tutorial-prereqs.md" >}} {{< version-check >}} * Make sure your Kubernetes cluster has a master version of 1.11.0 or higher. * Read about [custom resources](/docs/concepts/api-extension/custom-resources/). {{% /capture %}} {{% capture steps %}} ## Overview 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 versions. {{< note >}} Earlier iterations included a `version` field instead of `versions`. The `version` field is deprecated and optional, but if it is not empty, it must match the first item in the `versions` field. {{< /note >}} ## Specify multiple versions This example shows a CustomResourceDefinition with two versions. The comments in the YAML provide more context. ```yaml apiVersion: apiextensions.k8s.io/v1beta1 kind: CustomResourceDefinition metadata: # name must match the spec fields below, and be in the form: . name: crontabs.example.com spec: # group name to use for REST API: /apis// 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/// 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. ```shell 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 `/apis/example.com/v1beta1` and `/apis/example.com/v1`. ### Version priority 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 `beta` or `alpha` designation, and optional additional numeric versioning information. Broadly, a version string might look like `v2` or `v2beta1`. Versions are sorted using the following algorithm: - Entries that follow Kubernetes version patterns are sorted before those that do not. - For entries that follow Kubernetes version patterns, the numeric portions of the version string is sorted largest to smallest. - If the strings `beta` or `alpha` follow the first numeric portion, they sorted in that order, after the equivalent string without the `beta` or `alpha` suffix (which is presumed to be the GA version). - If another number follows the `beta`, or `alpha`, those numbers are also sorted from largest to smallest. - Strings that don't fit the above format are sorted alphabetically and the numeric portions are not treated specially. Notice that in the example below, `foo1` is 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: ```none - v10 - v2 - v1 - v11beta2 - v10beta3 - v3beta1 - v12alpha1 - v11alpha2 - foo1 - foo10 ``` For the example in [Specify multiple versions](#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 the version. ## Writing, reading, and updating versioned CustomResourceDefinition objects 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: 1. The storage version is `v1beta1`. You create an object. It is persisted in storage at version `v1beta1` 2. You add version `v1` to your CustomResourceDefinition and designate it as the storage version. 3. You read your object at version `v1beta1`, then you read the object again at version `v1`. Both returned objects are identical except for the apiVersion field. 4. You create a new object. It is persisted in storage at version `v1`. You now have two objects, one of which is at `v1beta1`, and the other of which is at `v1`. 5. You update the first object. It is now persisted at version `v1` since that is the current storage version. ### Previous storage versions 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. ## Upgrade existing objects to a new stored version When deprecating versions and dropping support, devise a storage upgrade procedure. The following is an example procedure to upgrade from `v1beta1` to `v1`. 1. Set `v1` as the storage in the CustomResourceDefinition file and apply it using kubectl. The `storedVersions` is now `v1beta1, v1`. 2. Write an upgrade procedure to list all existing objects and write them with the same content. This forces the backend to write objects in the current storage version, which is `v1`. 3. Update the CustomResourceDefinition `Status` by removing `v1beta1` from `storedVersions` field. {{% /capture %}}