Introduce VMO based clusters

Add support for Azure virtual machine scaleset orchestration mode vm (VMO) based Shoot clusters. Each worker pool will get its own VMO instead its of a shared resource like for AvailabilitySets based clusters. The Shoot cluster need to be non-zoned and have the annotation "alpha.azure.provider.extensions.gardener.cloud/vmo=true" to enable VMO which we currently treat as a preview feature. - In case the corresponding fault domain count in the CloudProfile changes then the VMO will be replaced. This will lead to a rolling update of the machines in each worker pool. - Orphan Gardener managed VMOs will be removed during the Worker reconcilation. So it is safe to be deployed into existing resource group without leaking resources. - VMO based clusters will make use of the Standard SKU Loadbalancer. - The NatGateway will be available for VMO clusters. This is a difference to AvailabilitySet based clusters which does not support NatGateway. - Accelerated network will work with VMO clusters. Other changes: - The Azure SDK is updated to support compute client in version 2020-06-30 (required to support VMO is min 2019-12-01) - VMO clusters will use the "vmss" version of the vm-controller in the Azure cloud-controller-manager (activated in the cloud-provider config via "vmType=vmss"). - A vmss client has been added to the client factory. - Added mocks for the client factory and the vmss client. - The Worker controller tests have been restructured partially to allow more reuse for the machine dependency tests. - The machineclass chart structure to configure AvailabilitySets has been alligned to the way to configure VMOs.
gardener · Jan 12, 2021 · cf0beff · cf0beff
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diff --git a/charts/internal/cloud-provider-config/templates/cloud-provider-config.tpl b/charts/internal/cloud-provider-config/templates/cloud-provider-config.tpl
@@ -15,6 +15,9 @@ loadBalancerSku: "basic"
 {{- else }}
 loadBalancerSku: "standard"
 {{- end }}
+{{- if hasKey .Values "vmType" }}
+vmType: "{{ .Values.vmType }}"
+{{- end }}
 cloudProviderBackoff: true
 cloudProviderBackoffRetries: 6
 cloudProviderBackoffExponent: 1.5

diff --git a/charts/internal/cloud-provider-config/values.yaml b/charts/internal/cloud-provider-config/values.yaml
@@ -12,3 +12,4 @@ securityGroupName: sgname
 region: location
 maxNodes: 0
 # acrIdentityClientId: identityClientID
+# vmType: standard
diff --git a/charts/internal/machineclass/templates/machineclass.yaml b/charts/internal/machineclass/templates/machineclass.yaml
@@ -24,9 +24,10 @@ spec:
     {{- if hasKey $machineClass "zone" }}
     zone: {{ $machineClass.zone }}
     {{- end }}
-    {{- if hasKey $machineClass "availabilitySetID" }}
-    availabilitySet:
-      id: {{ $machineClass.availabilitySetID }}
+    {{- if hasKey $machineClass "machineSet" }}
+    machineSet:
+      id: {{ $machineClass.machineSet.id }}
+      kind: {{ $machineClass.machineSet.kind }}
     {{- end }}
     {{- if hasKey $machineClass "identityID" }}
     identityID: {{ $machineClass.identityID }}

diff --git a/charts/internal/machineclass/values.yaml b/charts/internal/machineclass/values.yaml
@@ -34,7 +34,41 @@ machineClasses:
   network:
     vnet: my-vnet
     subnet: my-subnet-in-my-vnet
-  availabilitySetID: /subscriptions/subscription-id/resourceGroups/resource-group-name/providers/Microsoft.Compute/availabilitySets/availablity-set-name
+  machineSet:
+    id: /subscriptions/subscription-id/resourceGroups/resource-group-name/providers/Microsoft.Compute/availabilitySets/availablity-set-name
+    kind: availabilityset
+  tags:
+    Name: shoot-crazy-botany
+    kubernetes.io-cluster-shoot-crazy-botany: "1"
+    kubernetes.io-role-node: "1"
+  secret:
+    cloudConfig: abc
+  credentialsSecretRef:
+    name: cloudprovider
+    namespace: shoot-namespace
+  machineType: Standard_DS1_V2
+  image:
+    #urn: "CoreOS:CoreOS:Stable:1576.5.0"
+    id: "/subscriptions/<subscription ID where the gallery is located>/resourceGroups/myGalleryRG/providers/Microsoft.Compute/galleries/myGallery/images/myImageDefinition/versions/1.0.0"
+  osDisk:
+    size: 50
+    type: Standard_LRS
+# dataDisks:
+# - lun: 0
+#   caching: None
+#   diskSizeGB: 100
+#   storageAccountType: Standard_LRS
+#   name: sdb
+  sshPublicKey: ssh-rsa AAAAB3...
+- name: class-3-vmo
+  region: westeurope
+  resourceGroup: my-resource-group
+  network:
+    vnet: my-vnet
+    subnet: my-subnet-in-my-vnet
+  machineSet:
+    id: /subscriptions/subscription-id/resourceGroups/resource-group-name/providers/Microsoft.Compute/virtualmachinescaleset/vmo-name
+    kind: vmo
   tags:
     Name: shoot-crazy-botany
     kubernetes.io-cluster-shoot-crazy-botany: "1"

diff --git a/docs/usage-as-end-user.md b/docs/usage-as-end-user.md
@@ -257,3 +257,20 @@ All worker machines of the cluster will be automatically configured to use [Azur
 The prerequisites are that the cluster must be zoned, and the used machine type and operating system image version are compatible for Accelerated Networking.
 `Availability Set` based shoot clusters will not be enabled for accelerated networking even if the machine type and operating system support it, this is necessary because all machines from the availability set must be scheduled on special hardware, more daitls can be found [here](https://github.com/MicrosoftDocs/azure-docs/issues/10536).
 Supported machine types are listed in the CloudProfile in `.spec.providerConfig.machineTypes[].acceleratedNetworking` and the supported operating system image versions are defined in `.spec.providerConfig.machineImages[].versions[].acceleratedNetworking`.
+
+### Preview: Shoot clusters with VMSS Orchestration Mode VM (VMO)
+
+Azure Shoot clusters can be created with machines which are attached to an [Azure Virtual Machine ScaleSet orchestraion mode VM (VMO)](https://docs.microsoft.com/en-us/azure/virtual-machine-scale-sets/orchestration-modes).
+The orchestraion mode VM of Virtual Machine ScaleSet is currently in preview mode and not yet general available on Azure.
+
+Azure VMO are intended to replace Azure AvailabilitySet for non-zoned Azure Shoot clusters in the mid-term as VMO come with less disadvantages like no blocking machine operations or compability with `Standard` SKU loadbalancer etc.
+
+To configure an Azure Shoot cluster which make use of VMO you need to do the following:
+- The `InfrastructureConfig` of the Shoot configuration need to contain `.zoned=false`
+- Shoot resource need to have the following annotation assigned: `alpha.azure.provider.extensions.gardener.cloud/vmo=true`
+
+Some key facts about VMO based clusters:
+- Unlike regular non-zonal Azure Shoot clusters, which have a primary AvailabilitySet which is shared between all machines in all worker pools of a Shoot cluster, a VMO based cluster has an own VMO for each workerpool
+- In case the configuration of the VMO will change (e.g. amount of fault domains in a region change; configured in the CloudProfile) all machines of the worker pool need to be rolled
+- It is not possible to migrate an existing primary AvailabilitySet based Shoot cluster to VMO based Shoot cluster and vice versa
+- VMO based clusters are using `Standard` SKU LoadBalancers instead of `Basic` SKU LoadBalancers for AvailabilitySet based Shoot clusters
diff --git a/go.mod b/go.mod
@@ -3,7 +3,7 @@ module github.com/gardener/gardener-extension-provider-azure
 go 1.15
 
 require (
-	github.com/Azure/azure-sdk-for-go v44.0.0+incompatible
+	github.com/Azure/azure-sdk-for-go v49.2.0+incompatible
 	github.com/Azure/azure-storage-blob-go v0.7.0
 	github.com/Azure/go-autorest/autorest v0.10.1
 	github.com/Azure/go-autorest/autorest/adal v0.8.2

diff --git a/go.sum b/go.sum
@@ -15,20 +15,17 @@ github.com/Azure/azure-pipeline-go v0.2.1 h1:OLBdZJ3yvOn2MezlWvbrBMTEUQC72zAftRZ
 github.com/Azure/azure-pipeline-go v0.2.1/go.mod h1:UGSo8XybXnIGZ3epmeBw7Jdz+HiUVpqIlpz/HKHylF4=
 github.com/Azure/azure-sdk-for-go v39.0.0+incompatible/go.mod h1:9XXNKU+eRnpl9moKnB4QOLf1HestfXbmab5FXxiDBjc=
 github.com/Azure/azure-sdk-for-go v42.2.0+incompatible/go.mod h1:9XXNKU+eRnpl9moKnB4QOLf1HestfXbmab5FXxiDBjc=
-github.com/Azure/azure-sdk-for-go v44.0.0+incompatible h1:e82Yv2HNpS0kuyeCrV29OPKvEiqfs2/uJHic3/3iKdg=
-github.com/Azure/azure-sdk-for-go v44.0.0+incompatible/go.mod h1:9XXNKU+eRnpl9moKnB4QOLf1HestfXbmab5FXxiDBjc=
+github.com/Azure/azure-sdk-for-go v49.2.0+incompatible h1:23a1GeBzTLeT53StH9NDJyCMhxCH3awTZaw9ZYBcq78=
+github.com/Azure/azure-sdk-for-go v49.2.0+incompatible/go.mod h1:9XXNKU+eRnpl9moKnB4QOLf1HestfXbmab5FXxiDBjc=
 github.com/Azure/azure-storage-blob-go v0.7.0 h1:MuueVOYkufCxJw5YZzF842DY2MBsp+hLuh2apKY0mck=
 github.com/Azure/azure-storage-blob-go v0.7.0/go.mod h1:f9YQKtsG1nMisotuTPpO0tjNuEjKRYAcJU8/ydDI++4=
 github.com/Azure/go-ansiterm v0.0.0-20170929234023-d6e3b3328b78/go.mod h1:LmzpDX56iTiv29bbRTIsUNlaFfuhWRQBWjQdVyAevI8=
 github.com/Azure/go-autorest/autorest v0.9.0/go.mod h1:xyHB1BMZT0cuDHU7I0+g046+BFDTQ8rEZB0s4Yfa6bI=
-github.com/Azure/go-autorest/autorest v0.9.3 h1:OZEIaBbMdUE/Js+BQKlpO81XlISgipr6yDJ+PSwsgi4=
 github.com/Azure/go-autorest/autorest v0.9.3/go.mod h1:GsRuLYvwzLjjjRoWEIyMUaYq8GNUx2nRB378IPt/1p0=
 github.com/Azure/go-autorest/autorest v0.10.1 h1:uaB8A32IZU9YKs9v50+/LWIWTDHJk2vlGzbfd7FfESI=
 github.com/Azure/go-autorest/autorest v0.10.1/go.mod h1:/FALq9T/kS7b5J5qsQ+RSTUdAmGFqi0vUdVNNx8q630=
 github.com/Azure/go-autorest/autorest/adal v0.5.0/go.mod h1:8Z9fGy2MpX0PvDjB1pEgQTmVqjGhiHBW7RJJEciWzS0=
-github.com/Azure/go-autorest/autorest/adal v0.8.0 h1:CxTzQrySOxDnKpLjFJeZAS5Qrv/qFPkgLjx5bOAi//I=
 github.com/Azure/go-autorest/autorest/adal v0.8.0/go.mod h1:Z6vX6WXXuyieHAXwMj0S6HY6e6wcHn37qQMBQlvY3lc=
-github.com/Azure/go-autorest/autorest/adal v0.8.1 h1:pZdL8o72rK+avFWl+p9nE8RWi1JInZrWJYlnpfXJwHk=
 github.com/Azure/go-autorest/autorest/adal v0.8.1/go.mod h1:ZjhuQClTqx435SRJ2iMlOxPYt3d2C/T/7TiQCVZSn3Q=
 github.com/Azure/go-autorest/autorest/adal v0.8.2 h1:O1X4oexUxnZCaEUGsvMnr8ZGj8HI37tNezwY4npRqA0=
 github.com/Azure/go-autorest/autorest/adal v0.8.2/go.mod h1:ZjhuQClTqx435SRJ2iMlOxPYt3d2C/T/7TiQCVZSn3Q=
@@ -72,7 +69,6 @@ github.com/PuerkitoBio/urlesc v0.0.0-20160726150825-5bd2802263f2/go.mod h1:uGdko
 github.com/PuerkitoBio/urlesc v0.0.0-20170810143723-de5bf2ad4578 h1:d+Bc7a5rLufV/sSk/8dngufqelfh6jnri85riMAaF/M=
 github.com/PuerkitoBio/urlesc v0.0.0-20170810143723-de5bf2ad4578/go.mod h1:uGdkoq3SwY9Y+13GIhn11/XLaGBb4BfwItxLd5jeuXE=
 github.com/agnivade/levenshtein v1.0.1/go.mod h1:CURSv5d9Uaml+FovSIICkLbAUZ9S4RqaHDIsdSBg7lM=
-github.com/ahmetb/gen-crd-api-reference-docs v0.1.5 h1:OU+AFpBEhyclrQGx4I6zpCx5WvXiKqvFeeOASOmhKCY=
 github.com/ahmetb/gen-crd-api-reference-docs v0.1.5/go.mod h1:P/XzJ+c2+khJKNKABcm2biRwk2QAuwbLf8DlXuaL7WM=
 github.com/ahmetb/gen-crd-api-reference-docs v0.2.0 h1:YI/cAcRdNAHArfhGKcmCY5qMa32k/UyCZagLgabC5JY=
 github.com/ahmetb/gen-crd-api-reference-docs v0.2.0/go.mod h1:P/XzJ+c2+khJKNKABcm2biRwk2QAuwbLf8DlXuaL7WM=
@@ -92,7 +88,6 @@ github.com/asaskevich/govalidator v0.0.0-20190424111038-f61b66f89f4a/go.mod h1:l
 github.com/aws/aws-sdk-go v1.13.54/go.mod h1:ZRmQr0FajVIyZ4ZzBYKG5P3ZqPz9IHG41ZoMu1ADI3k=
 github.com/aws/aws-sdk-go v1.19.41/go.mod h1:KmX6BPdI08NWTb3/sm4ZGu5ShLoqVDhKgpiN924inxo=
 github.com/baiyubin/aliyun-sts-go-sdk v0.0.0-20180326062324-cfa1a18b161f/go.mod h1:AuiFmCCPBSrqvVMvuqFuk0qogytodnVFVSN5CeJB8Gc=
-github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973 h1:xJ4a3vCFaGF/jqvzLMYoU8P317H5OQ+Via4RmuPwCS0=
 github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24TaqPxmxbtue+5NUziq4I4S80YR8gNf3Q=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
@@ -158,7 +153,6 @@ github.com/emicklei/go-restful v2.9.6+incompatible/go.mod h1:otzb+WCGbkyDHkqmQmT
 github.com/envoyproxy/go-control-plane v0.9.1-0.20191026205805-5f8ba28d4473/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/protoc-gen-validate v0.1.0/go.mod h1:iSmxcyjqTsJpI2R4NaDN7+kN2VEUnK/pcBlmesArF7c=
 github.com/evanphx/json-patch v4.0.0+incompatible/go.mod h1:50XU6AFN0ol/bzJsmQLiYLvXMP4fmwYFNcr97nuDLSk=
-github.com/evanphx/json-patch v4.5.0+incompatible h1:ouOWdg56aJriqS0huScTkVXPC5IcNrDCXZ6OoTAWu7M=
 github.com/evanphx/json-patch v4.5.0+incompatible/go.mod h1:50XU6AFN0ol/bzJsmQLiYLvXMP4fmwYFNcr97nuDLSk=
 github.com/evanphx/json-patch v4.9.0+incompatible h1:kLcOMZeuLAJvL2BPWLMIj5oaZQobrkAqrL+WFZwQses=
 github.com/evanphx/json-patch v4.9.0+incompatible/go.mod h1:50XU6AFN0ol/bzJsmQLiYLvXMP4fmwYFNcr97nuDLSk=
@@ -167,7 +161,6 @@ github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5Kwzbycv
 github.com/frankban/quicktest v1.5.0/go.mod h1:jaStnuzAqU1AJdCO0l53JDCJrVDKcS03DbaAcR7Ks/o=
 github.com/frankban/quicktest v1.9.0 h1:jfEA+Psfr/pHsRJYPpHiNu7PGJnGctNxvTaM3K1EyXk=
 github.com/frankban/quicktest v1.9.0/go.mod h1:ui7WezCLWMWxVWr1GETZY3smRy0G4KWq9vcPtJmFl7Y=
-github.com/fsnotify/fsnotify v1.4.7 h1:IXs+QLmnXW2CcXuY+8Mzv/fWEsPGWxqefPtCP5CnV9I=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
 github.com/fsnotify/fsnotify v1.4.9 h1:hsms1Qyu0jgnwNXIxa+/V/PDsU6CfLf6CNO8H7IWoS4=
 github.com/fsnotify/fsnotify v1.4.9/go.mod h1:znqG4EE+3YCdAaPaxE2ZRY/06pZUdp0tY4IgpuI1SZQ=

diff --git a/hack/api-reference/api.md b/hack/api-reference/api.md
@@ -284,6 +284,20 @@ resources that are still using this version. Hence, it stores the used versions
 reconciliation is possible.</p>
 </td>
 </tr>
+<tr>
+<td>
+<code>vmoDependencies</code></br>
+<em>
+<a href="#azure.provider.extensions.gardener.cloud/v1alpha1.VmoDependency">
+[]VmoDependency
+</a>
+</em>
+</td>
+<td>
+<em>(Optional)</em>
+<p>VmoDependencies is a list of external VirtualMachineScaleSet Orchestration Mode VM (VMO) dependencies.</p>
+</td>
+</tr>
 </tbody>
 </table>
 <h3 id="azure.provider.extensions.gardener.cloud/v1alpha1.AvailabilitySet">AvailabilitySet
@@ -1313,6 +1327,58 @@ string
 </tr>
 </tbody>
 </table>
+<h3 id="azure.provider.extensions.gardener.cloud/v1alpha1.VmoDependency">VmoDependency
+</h3>
+<p>
+(<em>Appears on:</em>
+<a href="#azure.provider.extensions.gardener.cloud/v1alpha1.WorkerStatus">WorkerStatus</a>)
+</p>
+<p>
+<p>VmoDependency is dependency reference for a workerpool to a VirtualMachineScaleSet Orchestration Mode VM (VMO).</p>
+</p>
+<table>
+<thead>
+<tr>
+<th>Field</th>
+<th>Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>
+<code>poolName</code></br>
+<em>
+string
+</em>
+</td>
+<td>
+<p>PoolName is the name of the worker pool to which the VMO belong to.</p>
+</td>
+</tr>
+<tr>
+<td>
+<code>id</code></br>
+<em>
+string
+</em>
+</td>
+<td>
+<p>ID is the id of the VMO resource on Azure.</p>
+</td>
+</tr>
+<tr>
+<td>
+<code>name</code></br>
+<em>
+string
+</em>
+</td>
+<td>
+<p>Name is the name of the VMO resource on Azure.</p>
+</td>
+</tr>
+</tbody>
+</table>
 <hr/>
 <p><em>
 Generated with <a href="https://github.com/ahmetb/gen-crd-api-reference-docs">gen-crd-api-reference-docs</a>

diff --git a/pkg/apis/azure/helper/helper.go b/pkg/apis/azure/helper/helper.go
@@ -18,6 +18,7 @@ import (
 	"fmt"
 
 	api "github.com/gardener/gardener-extension-provider-azure/pkg/apis/azure"
+	"github.com/gardener/gardener-extension-provider-azure/pkg/azure"
 )
 
 // FindSubnetByPurpose takes a list of subnets and tries to find the first entry
@@ -115,3 +116,17 @@ func FindImageFromCloudProfile(cloudProfileConfig *api.CloudProfileConfig, image
 
 	return nil, fmt.Errorf("could not find an image for name %q in version %q", imageName, imageVersion)
 }
+
+// IsVmoRequired determines if VMO is required.
+func IsVmoRequired(infrastructureStatus *api.InfrastructureStatus) bool {
+	return !infrastructureStatus.Zoned && len(infrastructureStatus.AvailabilitySets) == 0
+}
+
+// HasShootVmoAlphaAnnotation determines if the passed Shoot annotations contain instruction to use VMO.
+func HasShootVmoAlphaAnnotation(shootAnnotations map[string]string) bool {
+	value, exists := shootAnnotations[azure.ShootVmoUsageAnnotation]
+	if exists && value == "true" {
+		return true
+	}
+	return false
+}
diff --git a/pkg/apis/azure/helper/helper_test.go b/pkg/apis/azure/helper/helper_test.go
@@ -17,6 +17,7 @@ package helper_test
 import (
 	api "github.com/gardener/gardener-extension-provider-azure/pkg/apis/azure"
 	. "github.com/gardener/gardener-extension-provider-azure/pkg/apis/azure/helper"
+	"github.com/gardener/gardener-extension-provider-azure/pkg/azure"
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/ginkgo/extensions/table"
@@ -139,6 +140,42 @@ var _ = Describe("Helper", func() {
 		Entry("valid image reference, only urn", makeProfileMachineImageWithIDandURN("ubuntu", "1", &profileURN, nil), "ubuntu", "1", &api.MachineImage{Name: "ubuntu", Version: "1", URN: &profileURN}),
 		Entry("valid image reference, only id", makeProfileMachineImageWithIDandURN("ubuntu", "1", nil, &profileID), "ubuntu", "1", &api.MachineImage{Name: "ubuntu", Version: "1", ID: &profileID}),
 	)
+
+	DescribeTable("#IsVmoRequired",
+		func(zoned bool, availabilitySet *api.AvailabilitySet, expectedVmoRequired bool) {
+			var infrastructureStatus = &api.InfrastructureStatus{
+				Zoned: zoned,
+			}
+			if availabilitySet != nil {
+				infrastructureStatus.AvailabilitySets = append(infrastructureStatus.AvailabilitySets, *availabilitySet)
+			}
+
+			Expect(IsVmoRequired(infrastructureStatus)).To(Equal(expectedVmoRequired))
+		},
+		Entry("should require a VMO", false, nil, true),
+		Entry("should not require VMO for zoned cluster", true, nil, false),
+		Entry("should not require VMO for a cluster with primary availabilityset (non zoned)", false, &api.AvailabilitySet{
+			ID:      "/my/azure/availabilityset/id",
+			Name:    "my-availabilityset",
+			Purpose: api.PurposeNodes,
+		}, false),
+	)
+
+	DescribeTable("#HasShootVmoAlphaAnnotation",
+		func(hasVmoAnnotaion, hasCorrectVmoAnnotationValue, expectedResult bool) {
+			var annotations = map[string]string{}
+			if hasVmoAnnotaion {
+				annotations[azure.ShootVmoUsageAnnotation] = "some-arbitrary-value"
+			}
+			if hasCorrectVmoAnnotationValue {
+				annotations[azure.ShootVmoUsageAnnotation] = "true"
+			}
+			Expect(HasShootVmoAlphaAnnotation(annotations)).To(Equal(expectedResult))
+		},
+		Entry("should return true as shoot annotations contain vmo alpha annotation with value true", true, true, true),
+		Entry("should return false as shoot annotations contain vmo alpha annotation with wrong value", true, false, false),
+		Entry("should return false as shoot annotations do not contain vmo alpha annotation", false, false, false),
+	)
 })
 
 func makeProfileMachineImages(name, urnVersion, idVersion string) []api.MachineImages {

diff --git a/pkg/apis/azure/types_worker.go b/pkg/apis/azure/types_worker.go
@@ -30,6 +30,9 @@ type WorkerStatus struct {
 	// resources that are still using this version. Hence, it stores the used versions in the provider status to ensure
 	// reconciliation is possible.
 	MachineImages []MachineImage
+
+	// VmoDependencies is a list of external VirtualMachineScaleSet Orchestration Mode VM (VMO) dependencies.
+	VmoDependencies []VmoDependency
 }
 
 // MachineImage is a mapping from logical names and versions to provider-specific machine image data.
@@ -45,3 +48,13 @@ type MachineImage struct {
 	// AcceleratedNetworking is an indicator if the image supports Azure accelerated networking.
 	AcceleratedNetworking *bool
 }
+
+// VmoDependency is dependency reference for a workerpool to a VirtualMachineScaleSet Orchestration Mode VM (VMO).
+type VmoDependency struct {
+	// PoolName is the name of the worker pool to which the VMO belong to.
+	PoolName string
+	// ID is the id of the VMO resource on Azure.
+	ID string
+	// Name is the name of the VMO resource on Azure.
+	Name string
+}
diff --git a/pkg/apis/azure/v1alpha1/types_worker.go b/pkg/apis/azure/v1alpha1/types_worker.go
@@ -32,6 +32,10 @@ type WorkerStatus struct {
 	// reconciliation is possible.
 	// +optional
 	MachineImages []MachineImage `json:"machineImages,omitempty"`
+
+	// VmoDependencies is a list of external VirtualMachineScaleSet Orchestration Mode VM (VMO) dependencies.
+	// +optional
+	VmoDependencies []VmoDependency `json:"vmoDependencies,omitempty"`
 }
 
 // MachineImage is a mapping from logical names and versions to provider-specific machine image data.
@@ -50,3 +54,13 @@ type MachineImage struct {
 	// +optional
 	AcceleratedNetworking *bool `json:"acceleratedNetworking,omitempty"`
 }
+
+// VmoDependency is dependency reference for a workerpool to a VirtualMachineScaleSet Orchestration Mode VM (VMO).
+type VmoDependency struct {
+	// PoolName is the name of the worker pool to which the VMO belong to.
+	PoolName string `json:"poolName"`
+	// ID is the id of the VMO resource on Azure.
+	ID string `json:"id"`
+	// Name is the name of the VMO resource on Azure.
+	Name string `json:"name"`
+}