🌱 KCP: Set MinItems=1 on ExternalEtcd.Endpoints

api/bootstrap/kubeadm/v1beta2/kubeadm_types.go

@@ -459,6 +459,7 @@ type LocalEtcd struct {
 type ExternalEtcd struct {
 	// endpoints of etcd members. Required for ExternalEtcd.
 	// +required
+	// +kubebuilder:validation:MinItems=1
 	// +kubebuilder:validation:MaxItems=50
 	// +kubebuilder:validation:items:MinLength=1
 	// +kubebuilder:validation:items:MaxLength=512

controlplane/kubeadm/internal/filters.go

@@ -428,6 +428,8 @@ func dropOmittableFields(spec *bootstrapv1.KubeadmConfigSpec) {
 		}
 		// NOTE: we are not dropping spec.ClusterConfiguration.Etcd.ExternalEtcd.Endpoints because this field
 		// doesn't have omitempty, so [] array is different from nil when serialized.
+		// But this field is also required and has MinItems=1, so it will
+		// never actually be nil or an empty array so that difference also won't trigger any rollouts.
 		if len(spec.ClusterConfiguration.APIServer.ExtraArgs) == 0 {
 			spec.ClusterConfiguration.APIServer.ExtraArgs = nil
 		}

controlplane/kubeadm/internal/filters_test.go

@@ -1896,7 +1896,9 @@ func TestOmittableFieldsClusterConfiguration(t *testing.T) {
 						PeerCertSANs:   nil,
 					},
 					External: &bootstrapv1.ExternalEtcd{
-						Endpoints: []string{}, // The field doesn't have omit empty.
+						// The field doesn't have omit empty. It also is required and has MinItems=1, so it will
+						// never actually be nil or an empty array so that difference also won't trigger any rollouts.
+						Endpoints: []string{},
 					},
 				},
 				APIServer: bootstrapv1.APIServer{