Registration Operator

The Registration Operator has 2 operators, Cluster Manager and Klusterlet. Cluster Manager installs the foundational components of OCM for the Hub cluster. And we can use the Klusterlet to install the agent components on the manged clusters when we import the manged clusters to the Hub.

The 2 operators are available on OperatorHub Cluster Manager and Klusterlet.

Concepts

Cluster Manager

The operator ClusterManager configures the controllers on the hub that govern registration, placement and work distribution for attached Klusterlets.

The controllers are all deployed in open-cluster-management-hub namespace on the Hub cluster.

Klusterlet

The operator Klusterlet represents the agent controllers registration and work on the managed cluster. The Klusterlet requires a secret named of bootstrap-hub-kubeconfig in the same namespace to allow API requests to the hub for the registration protocol.

The controllers are all deployed in open-cluster-management-agent namespace by default. The namespace can be specified in Klusterlet CR.

Get started with Kind

1. Create a cluster with kind

   kind create cluster 

2. Deploy

   export KUBECONFIG=$HOME/.kube/config
   make deploy

PLEASE NOTE: if the server address in kubeconfig is a domain name, the hub api server may not be accessible for klusterlet operator、 registration and work agent. In this case, you need to set hostAlias for klusterlet deployment and klusterlet CR explicitly.

More details about deployment

We mainly provide deployment in two scenarios:

1. All-in-one: using one cluster as hub and spoke at the same time.
2. Hub-spoke: using one cluster as hub and another cluster as spoke.

Deploy all-in-on deployment

1. Set the env variable KUBECONFIG to kubeconfig file path.

   export KUBECONFIG=$HOME/.kube/config

2. Deploy all components on the cluster.

   make deploy

3. To clean the environment, run make clean-deploy

Deploy hub-spoke deployment

1. Set env variables.

   export KUBECONFIG=$HOME/.kube/config

2. Switch to hub context and deploy hub components.

   kubectl config use-context {hub-context}
   make deploy-hub

   PLEASE NOTE: If you're running kubernetes in docker, the server address in kubeconfig may not be accessible for other clusters. In this case, you need to set HUB_KUBECONFIG explicitly.

   For example, if your clusters are created by kind, you need to use kind's command to export a kubeconfig of hub with an accessible server address. (The related issue)

   kind get kubeconfig --name {your kind cluster name} --internal > ./.hub-kubeconfig # ./.hub-kubeconfig is default value of HUB_KUBECONFIG 

3. Switch to spoke context and deploy agent components.

    kubectl config use-context {spoke context}
    make deploy-spoke

4. To clean the hub environment.

   kubectl config use-context {hub-context} 
   make clean-hub

5. To clean the spoke environment.

   kubectl config use-context {spoke-context} 
   make clean-spoke

Deploy hub(Clustermanager) with Hosted mode

1. Create 3 Kind clusters: management cluster, hub cluster and a managed cluster.

   kind create cluster --name hub
   cat <<EOF | kind create cluster --name management --config=-
   kind: Cluster
   apiVersion: kind.x-k8s.io/v1alpha4
   nodes:
   - role: control-plane
     extraPortMappings:
     - containerPort: 30443
       hostPort: 30443
       protocol: TCP
     - containerPort: 31443
       hostPort: 31443
       protocol: TCP
   EOF
   kind create cluster --name managed

2. Set the env variable KUBECONFIG to kubeconfig file path.

   export KUBECONFIG=$HOME/.kube/config

3. Get the EXTERNAL_HUB_KUBECONFIG kubeconfig.

   kind get kubeconfig --name hub --internal > ./.external-hub-kubeconfig  

4. Switch to management cluster and deploy hub components.

   kubectl config use-context {management-context}
   make deploy-hub-hosted

   After deploy hub successfully, the user needs to expose webhook-servers in the management cluster manually.

   cat <<EOF | kubectl apply -f -
   apiVersion: v1
   kind: Service
   metadata:
     name: cluster-manager-registration-webhook-external
     namespace: cluster-manager
   spec:
     type: NodePort
     selector:
       app: cluster-manager-registration-webhook
     ports:
       - port: 9443
         nodePort: 30443
   ---
   apiVersion: v1
   kind: Service
   metadata:
     name: cluster-manager-work-webhook-external
     namespace: cluster-manager
   spec:
     type: NodePort
     selector:
       app: cluster-manager-work-webhook
     ports:
       - port: 9443
         nodePort: 31443
   EOF

Deploy spoke(Klusterlet) with Hosted mode

We support deploy the Klusterlet(registration-agent, work-agent) outside of managed cluster, called Hosted mode, and we define the cluster where the Klusterlet runs as management-cluster.

1. Set env variables.

   export KUBECONFIG=$HOME/.kube/config

2. Switch to hub context and deploy hub components.

   kubectl config use-context {hub-context}
   make deploy-hub

   PLEASE NOTE: If you're running kubernetes in docker, the server address in kubeconfig may not be accessible for other clusters. In this case, you need to set HUB_KUBECONFIG explicitly.

   For example, if your clusters are created by kind, you need to use kind's command to export a kubeconfig of hub with an accessible server address. (The related issue)

   kind get kubeconfig --name {kind-hub-cluster-name} --internal > ./.hub-kubeconfig # ./.hub-kubeconfig is default value of HUB_KUBECONFIG

3. Switch to management context and deploy agent components on management cluster.

   kubectl config use-context {management-context}
   make deploy-spoke-hosted

   PLEASE NOTE: If you're running kubernetes in docker, the server address in kubeconfig may not be accessible for other clusters. In this case, you need to set EXTERNAL_MANAGED_KUBECONFIG explicitly.

   For example, if your clusters are created by kind, you need to use kind's command to export a kubeconfig of managed/spoke cluster with an accessible server address. (The related issue)

   kind get kubeconfig --name {kind-managed-cluster-name} --internal > ./.external-managed-kubeconfig # ./.external-managed-kubeconfig is default value of EXTERNAL_MANAGED_KUBECONFIG, it is only useful in Hosted mode.

4. To clean the hub environment.

   kubectl config use-context {hub-context}
   make clean-hub

5. To clean the spoke environment.

   kubectl config use-context {management-context}
   make clean-spoke-hosted
   

What is next

After a successful deployment, a certificatesigningrequest and a managedcluster will be created on the hub.

Switch to hub context and deploy hub components.

kubectl config use-context {hub-context}
kubectl get csr

Next approve the csr and set managedCluster to be accepted by hub with the following command

kubectl certificate approve {csr name}
kubectl patch managedcluster {cluster name} -p='{"spec":{"hubAcceptsClient":true}}' --type=merge
kubectl get managedcluster

Community, discussion, contribution, and support

Check the CONTRIBUTING Doc for how to contribute to the repo.

Communication channels

Slack channel: #open-cluster-mgmt

License

This code is released under the Apache 2.0 license. See the file LICENSE for more information.