fetch deleteMachine annotation from Machine

In certain circumstances the deleteMachine annotation isn't yet
propagated from the Machine to the AzureMachinePoolMachine. This can
result in deleting the wrong machines. This change ensures the owner
Machine's deleteMachine annotation is always considered.

Author: mweibel

azure/scope/machinepool.go

@@ -405,8 +405,31 @@ func (m *MachinePoolScope) applyAzureMachinePoolMachines(ctx context.Context) er
 	}
 
 	existingMachinesByProviderID := make(map[string]infrav1exp.AzureMachinePoolMachine, len(ampms))
-	for _, machine := range ampms {
-		existingMachinesByProviderID[machine.Spec.ProviderID] = machine
+	for _, ampm := range ampms {
+		machine, err := util.GetOwnerMachine(ctx, m.client, ampm.ObjectMeta)
+		if err != nil {
+			return fmt.Errorf("failed to find owner machine for %s/%s: %w", ampm.Namespace, ampm.Name, err)
+		}
+
+		if _, ampmHasDeleteAnnotation := ampm.Annotations[clusterv1.DeleteMachineAnnotation]; !ampmHasDeleteAnnotation {
+			// fetch Machine delete annotation from owner machine to AzureMachinePoolMachine.
+			// This ensures setting a deleteMachine annotation on the Machine has an effect on the AzureMachinePoolMachine
+			// and the deployment strategy, in case the automatic propagation of the annotation from Machine to AzureMachinePoolMachine
+			// hasn't been done yet.
+			if machine != nil && machine.Annotations != nil {
+				if _, hasDeleteAnnotation := machine.Annotations[clusterv1.DeleteMachineAnnotation]; hasDeleteAnnotation {
+					log.V(4).Info("fetched DeleteMachineAnnotation", "machine", ampm.Spec.ProviderID)
+					if ampm.Annotations == nil {
+						ampm.Annotations = make(map[string]string)
+					}
+					ampm.Annotations[clusterv1.DeleteMachineAnnotation] = machine.Annotations[clusterv1.DeleteMachineAnnotation]
+				}
+			}
+		} else {
+			log.V(4).Info("DeleteMachineAnnotation already set")
+		}
+
+		existingMachinesByProviderID[ampm.Spec.ProviderID] = ampm
 	}
 
 	// determine which machines need to be created to reflect the current state in Azure

azure/scope/machinepool_test.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"reflect"
 	"testing"
+	"time"
 
 	"github.com/Azure/azure-sdk-for-go/sdk/azidentity"
 	"github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/authorization/armauthorization/v2"
@@ -1414,6 +1415,46 @@ func TestMachinePoolScope_applyAzureMachinePoolMachines(t *testing.T) {
 				g.Expect(list.Items).Should(HaveLen(1))
 			},
 		},
+		{
+			Name: "if MachinePool is not externally managed, and Machines have delete machine annotation, and overProvisionCount > 0, delete machines with deleteMachine annotation first",
+			Setup: func(mp *expv1.MachinePool, amp *infrav1exp.AzureMachinePool, vmssState *azure.VMSS, cb *fake.ClientBuilder) {
+				mp.Spec.Replicas = ptr.To[int32](2)
+
+				mpm1, ampm1 := getAzureMachinePoolMachineWithOwnerMachine(1)
+
+				mpm2, ampm2 := getAzureMachinePoolMachineWithOwnerMachine(2)
+				mpm2.Annotations = map[string]string{
+					clusterv1.DeleteMachineAnnotation: time.Now().String(),
+				}
+
+				mpm3, ampm3 := getAzureMachinePoolMachineWithOwnerMachine(3)
+				objects := []client.Object{&mpm1, &ampm1, &mpm2, &ampm2, &mpm3, &ampm3}
+				cb.WithObjects(objects...)
+
+				vmssState.Instances = []azure.VMSSVM{
+					{
+						ID:   "/subscriptions/123/resourceGroups/my-rg/providers/Microsoft.Compute/virtualMachineScaleSets/my-vmss/virtualMachines/1",
+						Name: "ampm1",
+					},
+					{
+						ID:   "/subscriptions/123/resourceGroups/my-rg/providers/Microsoft.Compute/virtualMachineScaleSets/my-vmss/virtualMachines/2",
+						Name: "ampm2",
+					},
+					{
+						ID:   "/subscriptions/123/resourceGroups/my-rg/providers/Microsoft.Compute/virtualMachineScaleSets/my-vmss/virtualMachines/3",
+						Name: "ampm3",
+					},
+				}
+			},
+			Verify: func(g *WithT, amp *infrav1exp.AzureMachinePool, c client.Client, err error) {
+				g.Expect(err).NotTo(HaveOccurred())
+				list := clusterv1.MachineList{}
+				g.Expect(c.List(ctx, &list)).NotTo(HaveOccurred())
+				g.Expect(list.Items).Should(HaveLen(2))
+				g.Expect(list.Items[0].Name).Should(Equal("mpm1"))
+				g.Expect(list.Items[1].Name).Should(Equal("mpm3"))
+			},
+		},
 		{
 			Name: "if existing MachinePool is not present, reduce replicas",
 			Setup: func(mp *expv1.MachinePool, amp *infrav1exp.AzureMachinePool, vmssState *azure.VMSS, cb *fake.ClientBuilder) {