✨ Add externallyManagedReplicaCount field to MachinePool

config/crd/bases/cluster.x-k8s.io_machinepools.yaml

@@ -1011,6 +1011,14 @@ spec:
                   to.
                 minLength: 1
                 type: string
+              externallyManagedReplicaCount:
+                description: Whether the Replicas value is externally managed. This
+                  is useful when the infrastructure is a managed machine pool, or
+                  if the cluster-autoscaler is scaling the underlying cloud infrastructure
+                  directly outside of cluster-api. Set this to true if you wish the
+                  replica count to be managed outside of cluster-api. Defaults to
+                  false.
+                type: boolean
               failureDomains:
                 description: FailureDomains is the list of failure domains this MachinePool
                   should be attached to.

exp/api/v1alpha3/conversion.go

@@ -19,6 +19,7 @@ package v1alpha3
 import (
 	apimachineryconversion "k8s.io/apimachinery/pkg/conversion"
 	"sigs.k8s.io/cluster-api/exp/api/v1beta1"
+	utilconversion "sigs.k8s.io/cluster-api/util/conversion"
 	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
 	"sigs.k8s.io/controller-runtime/pkg/conversion"
 )
@@ -59,13 +60,36 @@ func Convert_v1beta1_MachinePool_To_v1alpha3_MachinePool(in *v1beta1.MachinePool
 func (src *MachinePool) ConvertTo(dstRaw conversion.Hub) error {
 	dst := dstRaw.(*v1beta1.MachinePool)
 
-	return Convert_v1alpha3_MachinePool_To_v1beta1_MachinePool(src, dst, nil)
+	if err := Convert_v1alpha3_MachinePool_To_v1beta1_MachinePool(src, dst, nil); err != nil {
+		return err
+	}
+
+	// Manually restore data.
+	restored := &v1beta1.MachinePool{}
+	if ok, err := utilconversion.UnmarshalData(src, restored); err != nil || !ok {
+		return err
+	}
+
+	if restored.Spec.ExternallyManagedReplicaCount != nil {
+		dst.Spec.ExternallyManagedReplicaCount = restored.Spec.ExternallyManagedReplicaCount
+	}
+
+	return nil
 }
 
 func (dst *MachinePool) ConvertFrom(srcRaw conversion.Hub) error {
 	src := srcRaw.(*v1beta1.MachinePool)
 
-	return Convert_v1beta1_MachinePool_To_v1alpha3_MachinePool(src, dst, nil)
+	if err := Convert_v1beta1_MachinePool_To_v1alpha3_MachinePool(src, dst, nil); err != nil {
+		return err
+	}
+
+	// Preserve Hub data on down-conversion except for metadata
+	if err := utilconversion.MarshalData(src, dst); err != nil {
+		return err
+	}
+
+	return nil
 }
 
 func (src *MachinePoolList) ConvertTo(dstRaw conversion.Hub) error {
@@ -79,3 +103,7 @@ func (dst *MachinePoolList) ConvertFrom(srcRaw conversion.Hub) error {
 
 	return Convert_v1beta1_MachinePoolList_To_v1alpha3_MachinePoolList(src, dst, nil)
 }
+
+func Convert_v1beta1_MachinePoolSpec_To_v1alpha3_MachinePoolSpec(in *v1beta1.MachinePoolSpec, out *MachinePoolSpec, s apimachineryconversion.Scope) error {
+	return autoConvert_v1beta1_MachinePoolSpec_To_v1alpha3_MachinePoolSpec(in, out, s)
+}

exp/api/v1alpha4/conversion.go

@@ -17,20 +17,45 @@ limitations under the License.
 package v1alpha4
 
 import (
+	apimachineryconversion "k8s.io/apimachinery/pkg/conversion"
 	v1beta1 "sigs.k8s.io/cluster-api/exp/api/v1beta1"
+	utilconversion "sigs.k8s.io/cluster-api/util/conversion"
 	"sigs.k8s.io/controller-runtime/pkg/conversion"
 )
 
 func (src *MachinePool) ConvertTo(dstRaw conversion.Hub) error {
 	dst := dstRaw.(*v1beta1.MachinePool)
 
-	return Convert_v1alpha4_MachinePool_To_v1beta1_MachinePool(src, dst, nil)
+	if err := Convert_v1alpha4_MachinePool_To_v1beta1_MachinePool(src, dst, nil); err != nil {
+		return err
+	}
+
+	// Manually restore data.
+	restored := &v1beta1.MachinePool{}
+	if ok, err := utilconversion.UnmarshalData(src, restored); err != nil || !ok {
+		return err
+	}
+
+	if restored.Spec.ExternallyManagedReplicaCount != nil {
+		dst.Spec.ExternallyManagedReplicaCount = restored.Spec.ExternallyManagedReplicaCount
+	}
+
+	return nil
 }
 
 func (dst *MachinePool) ConvertFrom(srcRaw conversion.Hub) error {
 	src := srcRaw.(*v1beta1.MachinePool)
 
-	return Convert_v1beta1_MachinePool_To_v1alpha4_MachinePool(src, dst, nil)
+	if err := Convert_v1beta1_MachinePool_To_v1alpha4_MachinePool(src, dst, nil); err != nil {
+		return err
+	}
+
+	// Preserve Hub data on down-conversion except for metadata
+	if err := utilconversion.MarshalData(src, dst); err != nil {
+		return err
+	}
+
+	return nil
 }
 
 func (src *MachinePoolList) ConvertTo(dstRaw conversion.Hub) error {
@@ -44,3 +69,7 @@ func (dst *MachinePoolList) ConvertFrom(srcRaw conversion.Hub) error {
 
 	return Convert_v1beta1_MachinePoolList_To_v1alpha4_MachinePoolList(src, dst, nil)
 }
+
+func Convert_v1beta1_MachinePoolSpec_To_v1alpha4_MachinePoolSpec(in *v1beta1.MachinePoolSpec, out *MachinePoolSpec, s apimachineryconversion.Scope) error {
+	return autoConvert_v1beta1_MachinePoolSpec_To_v1alpha4_MachinePoolSpec(in, out, s)
+}

exp/api/v1beta1/machinepool_types.go

@@ -59,6 +59,13 @@ type MachinePoolSpec struct {
 	// FailureDomains is the list of failure domains this MachinePool should be attached to.
 	// +optional
 	FailureDomains []string `json:"failureDomains,omitempty"`
+
+	// Whether the Replicas value is externally managed. This is useful when
+	// the infrastructure is a managed machine pool, or if the cluster-autoscaler is scaling
+	// the underlying cloud infrastructure directly outside of cluster-api. Set this to true
+	// if you wish the replica count to be managed outside of cluster-api. Defaults to false.
+	// +optional
+	ExternallyManagedReplicaCount *bool `json:"externallyManagedReplicaCount,omitempty"`
 }
 
 // ANCHOR_END: MachinePoolSpec