@startuml
title User scales down a KubeadmControlPlane
actor User

' -- GROUPS START ---

box #lightgreen
participant "API Server"
end box

box #violet
participant "KubeadmControlPlane Controller"
end box

box #lightgreen
participant "Workload Cluster API Server"
end box

' -- GROUPS END ---

User->"API Server":kubectl scale cp/my-control-plane -replicas=1
"API Server"-->>"KubeadmControlPlane Controller": KubeadmControlPlane Updated

"KubeadmControlPlane Controller"-> "KubeadmControlPlane Controller":Enqueues KubeadmControlPlane Reconcile

"KubeadmControlPlane Controller"-> "KubeadmControlPlane Controller":KubeadmControlPlane Controller Reconcile
activate "KubeadmControlPlane Controller"

note over "KubeadmControlPlane Controller": - ✅ KubeadmControlPlane.OwnerReferences \ncontains a Cluster

"KubeadmControlPlane Controller"->"API Server": Get Cluster
"KubeadmControlPlane Controller"<<--"API Server": Response

note over "KubeadmControlPlane Controller": - ✅ Cluster.Status.InfrastructureReady is true\n- ✅ KubeadmControlPlane instance is valid

"KubeadmControlPlane Controller"->"API Server": Get Machines matching label selector
"KubeadmControlPlane Controller"<<--"API Server": Response

note over "KubeadmControlPlane Controller": - Process for selecting a Machine to delete is TBD

opt #FFFFFFCC KubeadmControlPlane.Spec.Replicas >= 1, all existing Machines "Ready", num Machines > Replicas

"KubeadmControlPlane Controller"->"Workload Cluster API Server": Remove etcd Member

"KubeadmControlPlane Controller"->"Workload Cluster API Server": Modify kubeadm ConfigMap

"KubeadmControlPlane Controller"->"API Server": Delete a Machine

end

"KubeadmControlPlane Controller"->"API Server": Update KubeadmControlPlane
"KubeadmControlPlane Controller"<<--"API Server": Response

hide footbox
@enduml