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Using ClusterClass with CAPM3

ClusterClass is a feature of Cluster API that enables the cluster operators to create multiple clusters using a single general template. You can find detailed explanation of how to use a ClusterClass in the Cluster API documentation

Prerequisites

ClusterClass support enabled in CAPI

To use ClusterClass with CAPM3, experimental feature ClusterClass has to be enabled in CAPI deployment. You can find more info on how to enable ClusterClass support in The Cluster API Book.

Deploying cluster using ClusterClass

Deploying a ClusterClass

To create ClusterClass for CAPM3 a few objects has to be deployed in the management-cluster:

  • Metal3ClusterTemplate - a template that will be used by ClusterClass controller to instantiate the cluster.

  • KubeadmControlPlaneTemplate - a template used to create Kubeadm Control Plane for the instantiated cluster.

  • Metal3MachineTemplate - templates that will be used to create Metal3Machine objects. Can be defined separately for control plane and worker nodes.

  • KubeadmConfigTemplate - a template for Kubeadm config.

  • ClusterClass - the final object that references above objects and consolidates them into single cluster template definition.

You can find example of those objects in the example file available on the CAPM3 repository.

Deploying a Cluster

Definitions described above can be used to deploy multiple clusters. However some resources has to be deployed specifically for the cluster:

  • Metal3DataTemplate - should be created for both worker and control plane nodes in the cluster

  • IPPools - should be created per cluster if required.

  • Cluster - used to instantiate cluster using ClusterClass. You can change cluster behavior by overriding variables defined in the ClusterClass.

Example definitions of those resources can be found in the CAPM3 repository.

Tilt based development environment

If you want to further develop or test ClusterClass support you can use Tilt environment.

  1. Clone CAPM3 repository.

    git clone https://github.com/metal3-io/cluster-api-provider-metal3.git

  2. Generate Tilt settings that will enable ClusterClass support in CAPI.

    make tilt-settings-clusterclass

  3. Start Tilt.

    make tilt-up

  4. Generate ClusterClass based example.

    make generate-examples-clusterclass

  5. Deploy example ClusterClass, Cluster and all the dependencies.

    make deploy-examples-clusterclass