ClusterClaim

What is ClusterClaim?

ClusterClaim is a cluster-scoped API available to users on a managed cluster. The ClusterClaim objects are collected from the managed cluster and saved into the status of the corresponding ManagedCluster object on the hub.

Usage

ClusterCaim is used to specify additional properties of the managed cluster like the clusterID, version, vendor and cloud provider. We defined some reserved ClusterClaims like id.k8s.io which is a unique identifier for the managed cluster.

In addition to the reserved ClusterClaims, users can also customize 20 ClusterClaims by default. The maximum count of customized ClusterClaims can be configured via the flag max-custom-cluster-claims of registration agent on the managed cluster.

The ClusterClaim with the label open-cluster-management.io/spoke-only will not be synced to the status of ManagedCluster.

Example

Here is a ClusterClaim example specifying a id.k8s.io:

apiVersion: cluster.open-cluster-management.io/v1alpha1
kind: ClusterClaim
metadata:
  name: id.k8s.io
spec:
  value: myCluster

After applying the ClusterClaim above to any managed cluster, the value of the ClusterClaim is reflected in the ManagedCluster on the hub cluster:

apiVersion: cluster.open-cluster-management.io/v1
kind: ManagedCluster
metadata: ...
spec: ...
status:
  clusterClaims:
    - name: id.k8s.io
      value: myCluster

About-API Support in Open Cluster Management

Open Cluster Management (OCM) supports the use of ClusterProperty via the about-api, which allows administrators to define and expose cluster-scoped properties. These properties are synced to the managed cluster’s ManagedCluster status and can coexist with ClusterClaim but take precedence if a same-named property exists.

Enabling the Feature

To enable the ClusterProperty feature on the spoke cluster, the ClusterProperty feature gate must be set on the Klusterlet component. This can be done by setting the feature gate in the Klusterlet configuration:

featureGates:
  ClusterProperty: "true"

Ensure that the feature gate is enabled appropriately based on your cluster management strategy.

Using ClusterProperty

Creating a ClusterProperty

Cluster administrators can create a ClusterProperty custom resource in the spoke cluster. The following is an example YAML for creating a ClusterProperty:

apiVersion: about.k8s.io/v1alpha1
kind: ClusterProperty
metadata:
  name: example-property
spec:
  value: "example-value"

Once created, the ClusterProperty will be automatically synced to the hub cluster and reflected within the ManagedCluster resource’s status.

Syncing Existing Properties

After enabling the feature, any existing ClusterProperty resources will be synced to the ManagedCluster status on the hub cluster.

Example: If example-property with value example-value already exists on the spoke cluster, its value will populate into the ManagedCluster as:

status:
  clusterClaims:
    - name: "example-property"
      value: "example-value"

Handling Conflicts with ClusterClaim

In case a ClusterClaim resource with the same name as a ClusterProperty exists, the ClusterProperty will take precedence and the corresponding ClusterClaim will be ignored.

Updating ClusterProperties

Updating the value of an existing ClusterProperty will automatically reflect the change in the managed cluster’s status:

spec:
  value: "updated-value"

Deleting ClusterProperties

When a ClusterProperty is deleted from the spoke cluster, its corresponding entry in the ManagedCluster status is removed:

kubectl delete clusterproperty example-property

This will result in the removal of the example-property from the ManagedCluster status on the hub cluster.

Additional Notes

• Both ClusterProperty and ClusterClaim can co-exist, with ClusterProperty taking precedence in naming conflicts.
• The feature uses the existing OCM infrastructure for status synchronization, ensuring minimal disruption to ongoing operations.
• Ensure compatibility and testing in your environment before enabling the ClusterProperty feature gate in production settings.