Managing Clusters Provisioned by Cluster API Providers

How to Work with Cluster API Providers

The experimental feature ClusterResourceSet in Cluster API allows users to automatically install additional components onto workload clusters when the workload clusters are provisioned. With the help of this, clusters provisioned by Cluster API providers can be discovered and automatically get registered starting from Clusternet v0.12.0.

At a high level, using ClusterResourceSet to install clusternet-agent automatically looks like this:

  1. Make sure experimental features ClusterResourceSet are enabled on your Cluster API management cluster.
  2. Create a Secret in your Cluster API management cluster. that contains all the information to configure clusternet-agent, such as bootstrap token, parent cluster endpoint, container image.
  3. clusternet-hub connects to your Cluster API management cluster and watches all the clusters that are ready.
  4. clusternet-hub creates a ClusterResourceSet that will match all the workload clusters in the same namespace.

The sections below describe each of these steps in more detail.

Enabling Experimental Features

If you have not initialized the Cluster API management cluster, the preferred way to enable experimental features is to use a setting in the clusterctl configuration file or its environment variable equivalent. Specifically, putting EXP_CLUSTER_RESOURCE_SET: "true" in the clusterctl configuration file or using export EXP_CLUSTER_RESOURCE_SET=true before initializing the management cluster with clusterctl init will enable the ClusterResourceSet functionality.

You can also manually enable experimental features by directly modifying Deployment capi-controller-manager in the capi-system namespace.

- args:
    - --metrics-addr=
    - --enable-leader-election
    - --feature-gates=MachinePool=false,ClusterResourceSet=true
    - /manager

Creating a Secret for Cluster

You have to set right parameters for clusternet-agent, such as where should the clusters be registered to, the container image version and the bootstrap token for cluster registration.

$ wget
$ \
  PARENTURL=https://<CHANGEME>:6443 \
  REGTOKEN=07401b.f395accd246ae52d \
  envsubst < ./clusternet_clusterapi_secret.yaml | kubectl apply -f -

Please remember to slightly modify the values above to yours.

You can refer to how to generate token for cluster registration when setting REGTOKEN.

Configuring clusternet-hub

For clusternet-hub, it needs to know where the Cluster API management cluster is. You can specify an accessible kubeconfig file to flag --cluster-api-kubeconfig.

--cluster-api-kubeconfig string                   Path to a kubeconfig file pointing at the management cluster for cluster-api.

You can mount this file as a volume to clusternet-hub pods.

ClusterResourceSet Will Be Automatically Created

In your Cluster API management cluster, you can find ClusterResourceSets are automatically created.

$ kubectl --kubeconfig=/etc/clusternet/capi.conf get clusters -A
NAMESPACE   NAME              PHASE         AGE     VERSION
default     capi-quickstart   Provisioned   3h21m   v1.24.0
$ kubectl --kubeconfig=/etc/clusternet/capi.conf get clusterresourceset -A
NAMESPACE   NAME                     AGE
default     clusternet-cluster-api   3h46m

When you list all the pods running in your provisioned workload clusters, you can find clusternet-agent are deployed as well.

$ kubectl get pod --kubeconfig=capi-quickstart.config -A
NAMESPACE           NAME                                                  READY   STATUS    RESTARTS   AGE
clusternet-system   clusternet-agent-bf56c7cfb-6gvpj                      1/1     Running   0          7m11s
clusternet-system   clusternet-agent-bf56c7cfb-bfdt7                      1/1     Running   0          7m11s
clusternet-system   clusternet-agent-bf56c7cfb-bxvcn                      1/1     Running   0          7m11s
kube-system         coredns-6d4b75cb6d-89tb4                              1/1     Running   0          7m11s
kube-system         coredns-6d4b75cb6d-lpbsp                              1/1     Running   0          7m11s
kube-flannel        kube-flannel-ds-bgjv2                                 1/1     Running   0          7m11s
kube-flannel        kube-flannel-ds-7h6xp                                 1/1     Running   0          7m11s
kube-system         etcd-capi-quickstart-4sz8d-jfw9v                      1/1     Running   0          7m18s
kube-system         kube-apiserver-capi-quickstart-4sz8d-jfw9v            1/1     Running   0          7m19s
kube-system         kube-controller-manager-capi-quickstart-4sz8d-jfw9v   1/1     Running   0          7m19s
kube-system         kube-proxy-85ms9                                      1/1     Running   0          6m42s
kube-system         kube-proxy-dfb9x                                      1/1     Running   0          7m12s
kube-system         kube-scheduler-capi-quickstart-4sz8d-jfw9v            1/1     Running   0          7m18s

Last modified June 2, 2023: add doc on feed inventory (#86) (db1bc3b)