fix(machinepool): clear VirtualMachineProfile if no model/custom data update

azure/scope/machinepool.go

@@ -81,6 +81,7 @@
 		capiMachinePoolPatchHelper *patch.Helper
 		vmssState                  *azure.VMSS
 		cache                      *MachinePoolCache
+		skuCache                   *resourceskus.Cache
 	}
 
 	// NodeStatus represents the status of a Kubernetes node.
@@ -164,12 +165,15 @@
 			return err
 		}
 
-		skuCache, err := resourceskus.GetCache(m, m.Location())
-		if err != nil {
-			return err
+		if m.skuCache == nil {
+			skuCache, err := resourceskus.GetCache(m, m.Location())
+			if err != nil {
+				return errors.Wrap(err, "failed to init resourceskus cache")
+			}
+			m.skuCache = skuCache
 		}
 
-		m.cache.VMSKU, err = skuCache.Get(ctx, m.AzureMachinePool.Spec.Template.VMSize, resourceskus.VirtualMachines)
+		m.cache.VMSKU, err = m.skuCache.Get(ctx, m.AzureMachinePool.Spec.Template.VMSize, resourceskus.VirtualMachines)
 		if err != nil {
 			return errors.Wrapf(err, "failed to get VM SKU %s in compute api", m.AzureMachinePool.Spec.Template.VMSize)
 		}
@@ -222,10 +226,8 @@
 	}
 
 	if m.cache != nil {
-		if m.HasReplicasExternallyManaged(ctx) {
-			spec.ShouldPatchCustomData = m.cache.HasBootstrapDataChanges
-			log.V(4).Info("has bootstrap data changed?", "shouldPatchCustomData", spec.ShouldPatchCustomData)
-		}
+		spec.ShouldPatchCustomData = m.cache.HasBootstrapDataChanges
+		log.V(4).Info("has bootstrap data changed?", "shouldPatchCustomData", spec.ShouldPatchCustomData)
 		spec.VMSSExtensionSpecs = m.VMSSExtensionSpecs()
 		spec.SKU = m.cache.VMSKU
 		spec.VMImage = m.cache.VMImage
@@ -705,11 +707,9 @@
 		if err := m.updateReplicasAndProviderIDs(ctx); err != nil {
 			return errors.Wrap(err, "failed to update replicas and providerIDs")
 		}
-		if m.HasReplicasExternallyManaged(ctx) {
-			if err := m.updateCustomDataHash(ctx); err != nil {
-				// ignore errors to calculating the custom data hash since it's not absolutely crucial.
-				log.V(4).Error(err, "unable to update custom data hash, ignoring.")
-			}
+		if err := m.updateCustomDataHash(ctx); err != nil {
+			// ignore errors to calculating the custom data hash since it's not absolutely crucial.
+			log.V(4).Error(err, "unable to update custom data hash, ignoring.")
 		}
 	}
 

azure/scope/machinepool_test.go

@@ -18,13 +18,17 @@ package scope
 
 import (
 	"context"
+	"crypto/sha256"
+	"encoding/base64"
 	"fmt"
+	"io"
 	"reflect"
 	"testing"
 	"time"
 
 	"github.com/Azure/azure-sdk-for-go/sdk/azidentity"
 	"github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/authorization/armauthorization/v2"
+	"github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/compute/armcompute/v5"
 	azureautorest "github.com/Azure/go-autorest/autorest/azure"
 	"github.com/Azure/go-autorest/autorest/azure/auth"
 	. "github.com/onsi/gomega"
@@ -1576,3 +1580,148 @@ func TestMachinePoolScope_applyAzureMachinePoolMachines(t *testing.T) {
 		})
 	}
 }
+
+func TestBootstrapDataChanges(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	scheme := runtime.NewScheme()
+	_ = clusterv1.AddToScheme(scheme)
+	_ = infrav1.AddToScheme(scheme)
+	_ = infrav1exp.AddToScheme(scheme)
+	_ = corev1.AddToScheme(scheme)
+
+	var (
+		g        = NewWithT(t)
+		mockCtrl = gomock.NewController(t)
+		cb       = fake.NewClientBuilder().WithScheme(scheme)
+		cluster  = &clusterv1.Cluster{
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      "cluster1",
+				Namespace: "default",
+			},
+			Spec: clusterv1.ClusterSpec{
+				InfrastructureRef: &corev1.ObjectReference{
+					Name: "azCluster1",
+				},
+			},
+			Status: clusterv1.ClusterStatus{
+				InfrastructureReady: true,
+			},
+		}
+		azureCluster = &infrav1.AzureCluster{
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      "azCluster1",
+				Namespace: "default",
+			},
+			Spec: infrav1.AzureClusterSpec{
+				AzureClusterClassSpec: infrav1.AzureClusterClassSpec{
+					Location: "test",
+				},
+			},
+		}
+		mp = &expv1.MachinePool{
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      "mp1",
+				Namespace: "default",
+				OwnerReferences: []metav1.OwnerReference{
+					{
+						Name:       "cluster1",
+						Kind:       "Cluster",
+						APIVersion: clusterv1.GroupVersion.String(),
+					},
+				},
+			},
+			Spec: expv1.MachinePoolSpec{
+				Template: clusterv1.MachineTemplateSpec{
+					Spec: clusterv1.MachineSpec{
+						Bootstrap: clusterv1.Bootstrap{
+							DataSecretName: ptr.To("mp-secret"),
+						},
+						Version: ptr.To("v1.31.0"),
+					},
+				},
+			},
+		}
+		bootstrapData     = "test"
+		bootstrapDataHash = sha256Hash(base64.StdEncoding.EncodeToString([]byte(bootstrapData)))
+		bootstrapSecret   = corev1.Secret{
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      "mp-secret",
+				Namespace: "default",
+			},
+			Data: map[string][]byte{"value": []byte(bootstrapData)},
+		}
+		amp = &infrav1exp.AzureMachinePool{
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      "amp1",
+				Namespace: "default",
+				OwnerReferences: []metav1.OwnerReference{
+					{
+						Name:       "mp1",
+						Kind:       "MachinePool",
+						APIVersion: expv1.GroupVersion.String(),
+					},
+				},
+				Annotations: map[string]string{
+					azure.CustomDataHashAnnotation: fmt.Sprintf("%x", bootstrapDataHash),
+				},
+			},
+			Spec: infrav1exp.AzureMachinePoolSpec{
+				Template: infrav1exp.AzureMachinePoolMachineTemplate{
+					Image: &infrav1.Image{},
+					NetworkInterfaces: []infrav1.NetworkInterface{
+						{
+							SubnetName: "test",
+						},
+					},
+					VMSize: "VM_SIZE",
+				},
+			},
+		}
+		vmssState = &azure.VMSS{}
+	)
+	defer mockCtrl.Finish()
+
+	s := &MachinePoolScope{
+		client: cb.
+			WithObjects(&bootstrapSecret).
+			Build(),
+		ClusterScoper: &ClusterScope{
+			Cluster:      cluster,
+			AzureCluster: azureCluster,
+		},
+		skuCache: resourceskus.NewStaticCache([]armcompute.ResourceSKU{
+			{
+				Name: ptr.To("VM_SIZE"),
+			},
+		}, "test"),
+		MachinePool:      mp,
+		AzureMachinePool: amp,
+		vmssState:        vmssState,
+	}
+
+	g.Expect(s.InitMachinePoolCache(ctx)).NotTo(HaveOccurred())
+
+	spec := s.ScaleSetSpec(ctx)
+	sSpec := spec.(*scalesets.ScaleSetSpec)
+	g.Expect(sSpec.ShouldPatchCustomData).To(Equal(false))
+
+	amp.Annotations[azure.CustomDataHashAnnotation] = "old"
+
+	// reset cache to be able to build up the cache again
+	s.cache = nil
+	g.Expect(s.InitMachinePoolCache(ctx)).NotTo(HaveOccurred())
+
+	spec = s.ScaleSetSpec(ctx)
+	sSpec = spec.(*scalesets.ScaleSetSpec)
+	g.Expect(sSpec.ShouldPatchCustomData).To(Equal(true))
+}
+
+func sha256Hash(text string) []byte {
+	h := sha256.New()
+	_, err := io.WriteString(h, text)
+	if err != nil {
+		panic(err)
+	}
+	return h.Sum(nil)
+}

azure/services/scalesets/scalesets_test.go

@@ -741,8 +741,8 @@ func newWindowsVMSSSpec() ScaleSetSpec {
 	return vmss
 }
 
-func newDefaultExistingVMSS(vmSize string) armcompute.VirtualMachineScaleSet {
-	vmss := newDefaultVMSS(vmSize)
+func newDefaultExistingVMSS() armcompute.VirtualMachineScaleSet {
+	vmss := newDefaultVMSS("VM_SIZE")
 	vmss.ID = ptr.To("subscriptions/1234/resourceGroups/my_resource_group/providers/Microsoft.Compute/virtualMachines/my-vm")
 	return vmss
 }

azure/services/scalesets/spec.go

@@ -93,6 +93,9 @@ func (s *ScaleSetSpec) OwnerResourceName() string {
 }
 
 func (s *ScaleSetSpec) existingParameters(ctx context.Context, existing interface{}) (parameters interface{}, err error) {
+	ctx, log, done := tele.StartSpanWithLogger(ctx, "scalesets.ScaleSetSpec.existingParameters")
+	defer done()
+
 	existingVMSS, ok := existing.(armcompute.VirtualMachineScaleSet)
 	if !ok {
 		return nil, errors.Errorf("%T is not an armcompute.VirtualMachineScaleSet", existing)
@@ -132,6 +135,15 @@ func (s *ScaleSetSpec) existingParameters(ctx context.Context, existing interfac
 		return nil, nil
 	}
 
+	// if there are no model changes and no change in custom data, remove VirtualMachineProfile to avoid unnecessary VMSS model
+	// updates.
+	if !hasModelChanges && !s.ShouldPatchCustomData {
+		log.V(4).Info("removing virtual machine profile from parameters", "hasModelChanges", hasModelChanges, "shouldPatchCustomData", s.ShouldPatchCustomData)
+		vmss.Properties.VirtualMachineProfile = nil
+	} else {
+		log.V(4).Info("has changes, not removing virtual machine profile from parameters", "hasModelChanges", hasModelChanges, "shouldPatchCustomData", s.ShouldPatchCustomData)
+	}
+
 	return vmss, nil
 }