ASO Managed Clusters (AKS)

  • Feature status: alpha, not experimental, fully supported
  • Feature gate: MachinePool=true

New in CAPZ v1.15.0 is a new flavor of APIs that addresses the following limitations of the existing CAPZ APIs for advanced use cases for provisioning AKS clusters:

  • A limited set of Azure resource types can be represented.
  • A limited set of Azure resource topologies can be expressed. e.g. Only a single Virtual Network resource can be reconciled for each CAPZ-managed AKS cluster.
  • For each Azure resource type supported by CAPZ, CAPZ generally only uses a single Azure API version to define resources of that type.
  • For each Azure API version known by CAPZ, only a subset of fields defined in that version by the Azure API spec are exposed by the CAPZ API.

This new API defines new AzureASOManagedCluster, AzureASOManagedControlPlane, and AzureASOManagedMachinePool resources. An AzureASOManagedCluster might look like this:

apiVersion: infrastructure.cluster.x-k8s.io/v1alpha1
kind: AzureASOManagedCluster
metadata:
  name: my-cluster
  namespace: default
spec:
  resources:
  - apiVersion: resources.azure.com/v1api20200601
    kind: ResourceGroup
    metadata:
      name: my-resource-group
    spec:
      location: eastus

See here for a full AKS example using all the new resources.

The main element of the new API is spec.resources in each new resource, which defines arbitrary, literal ASO resources inline to be managed by CAPZ. These inline ASO resource definitions take the place of almost all other configuration currently defined by CAPZ. e.g. Instead of a CAPZ-specific spec.location field on the existing AzureManagedControlPlane, the same value would be expected to be set on an ASO ManagedCluster resource defined in an AzureASOManagedControlPlane’s spec.resources. This pattern allows users to define, in full, any ASO-supported version of a resource type in any of these new CAPZ resources.

The obvious tradeoff with this new style of API is that CAPZ resource definitions can become more verbose for basic use cases. To address this, CAPZ still offers flavor templates that use this API with all of the boilerplate predefined to serve as a starting point for customization.

The overall theme of this API is to leverage ASO as much as possible for representing Azure resources in the Kubernetes API, thereby making CAPZ the thinnest possible translation layer between ASO and Cluster API.

This experiment will help inform CAPZ whether this pattern may be a candidate for a potential v2 API. This functionality is enabled by default and can be disabled with the ASOAPI feature flag (set by the EXP_ASO_API environment variable). Please try it out and offer any feedback!