open-cluster-management/solutions/multiple-agents-hosted

Manage a cluster with multiple agents in hosted mode

The scripts provided in this doc help you to setup an Open Cluster Management (OCM) environment with Kind clusters where a single cluster is managed by two hubs via two agents installed on the managed cluster. The agents of the second hub runs in the hosted mode on a hosting cluster.

Prerequisite

• kind must be installed on your local machine. The Kubernetes version must be >= 1.19, see kind user guide for more details.

• Download and install clusteradm. For Linux OS, run the following commands:

  wget -qO- https://github.com/open-cluster-management-io/clusteradm/releases/latest/download/clusteradm_linux_amd64.tar.gz | sudo tar -xvz -C /usr/local/bin/
  
  sudo chmod +x /usr/local/bin/clusteradm
  

  Note: In order to run the scripts provided in this doc successfully, the clusteradm version must be > 0.7.1. You can also build it from the latest source code that contains the desired bug fixes.

Setup the first hub cluster

Run ./setup-hub1.sh. It creates two kind clusters:

• hub1. It is initialized as a OCM hub cluster.
• cluster1. It joins the hub1 as a managed cluster in the default mode.
  

Once it is done, you can then list the managed clusters on hub1 with command below.

kubectl get managedclusters
NAME       HUB ACCEPTED   MANAGED CLUSTER URLS                  JOINED   AVAILABLE   AGE
cluster1   true           https://cluster1-control-plane:6443                        29s

The managed cluster cluster1 joins hub1 in the default mode and its Klusterlet resource is created on the managed cluster.

kubectl get klusterlet
NAME         AGE
klusterlet   1m

And the OCM agent of hub1 is installed under namespace open-cluster-management-agent on the managed cluster. Another namespace open-cluster-management-agent-addon is created too for add-ons which might be installed in future for this managed cluster.

kubectl  get ns
NAME                                  STATUS   AGE
default                               Active   7m34s
kube-node-lease                       Active   7m34s
kube-public                           Active   7m34s
kube-system                           Active   7m34s
local-path-storage                    Active   7m30s
open-cluster-management               Active   7m27s
open-cluster-management-agent         Active   7m27s
open-cluster-management-agent-addon   Active   7m11s

Setup the second hub cluster

Run ./setup-hub2.sh. It creates two more Kind clusters:

• hub2. It is initialized as the second OCM hub cluster.
• hosting. It is used as the hosting cluster on which the OCM agent of hub2 is running.

The script also joins the previously created Kind cluster cluster1 to hub2 as a managed cluster in the hosted mode. Once it is done, you can list the managed clusters on hub2 with command below.

kubectl get managedclusters
NAME       HUB ACCEPTED   MANAGED CLUSTER URLS                  JOINED   AVAILABLE   AGE
cluster1   true           https://cluster1-control-plane:6443   True     True        38s

Since the managed cluster cluster1 joins in the hosted mode, its Klusterlet resource is created on the hosting cluster instead of the managed cluster.

kubectl get klusterlet
NAME                       AGE
klusterlet-hosted-cuz6ia   53s

The OCM agent of hub2 is installed under namespace klusterlet-hosted-cuz6ia on the hosting cluster as well.

kubectl  get ns
NAME                       STATUS   AGE
default                    Active   77s
klusterlet-hosted-cuz6ia   Active   57s
kube-node-lease            Active   77s
kube-public                Active   77s
kube-system                Active   77s
local-path-storage         Active   72s
open-cluster-management    Active   57s

Some namespaces, like open-cluster-management-klusterlet-hosted-cuz6ia and open-cluster-management-klusterlet-hosted-cuz6ia-addon, are created on the managed cluster cluster1 which are required by the OCM agent of hub2 running in the hosted mode.

kubectl  get ns
NAME                                                     STATUS   AGE
default                                                  Active   4m25s
kube-node-lease                                          Active   4m25s
kube-public                                              Active   4m25s
kube-system                                              Active   4m25s
local-path-storage                                       Active   4m21s
open-cluster-management                                  Active   4m12s
open-cluster-management-agent                            Active   4m12s
open-cluster-management-agent-addon                      Active   4m3s
open-cluster-management-klusterlet-hosted-cuz6ia         Active   78s
open-cluster-management-klusterlet-hosted-cuz6ia-addon   Active   78s