Repository: kubernetes-sigs/cloud-provider-azure (go)

Issue:
Should remove LB backend pool reference from VMSS with 0 capacity when updating backend pool type to nodeIP
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#### What happened:

We only decouple VMSS with non-zero capacity from the LB when updating from NIC to IP-based Load Balancer.

#### What you expected to happen:

VMSS with zero capacity should also be decoupled from the LB.

#### How to reproduce it (as minimally and precisely as possible):

#### Anything else we need to know?:

#### Environment:

- Kubernetes version (use `kubectl version`):
- Cloud provider or hardware configuration:
- OS (e.g: `cat /etc/os-release`):
- Kernel (e.g. `uname -a`):
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- Network plugin and version (if this is a network-related bug):
- Others:


Pull request:
[release-1.25] fix: decouple vmss with 0 instance from lb when deleting the service
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/kind bug

#### What this PR does / why we need it:

We parse the id of ipConfigs in the lb backend pool to determine what vmss are needed to be decoupled from the lb. But for those with 0 instance, they cannot be decoupled since there is no corresponding ipConfigs in the lb. This PR checks all cached vmss, if it is bound with the lb, we decouple it.

#### Which issue(s) this PR fixes:
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Fixes #2443 

#### Special notes for your reviewer:

#### Does this PR introduce a user-facing change?
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```release-note
fix: decouple vmss with 0 instance from lb when deleting the service
```

#### Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

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Patch:
diff --git a/pkg/provider/azure_vmss.go b/pkg/provider/azure_vmss.go
index 929cf4149..96afbe2a0 100644
--- a/pkg/provider/azure_vmss.go
+++ b/pkg/provider/azure_vmss.go
@@ -1518,22 +1518,72 @@ func getScaleSetAndResourceGroupNameByIPConfigurationID(ipConfigurationID string
 	return scaleSetName, resourceGroup, nil
 }
 
-func (ss *ScaleSet) ensureBackendPoolDeletedFromVMSS(service *v1.Service, backendPoolID, vmSetName string, ipConfigurationIDs []string) error {
+func (ss *ScaleSet) ensureBackendPoolDeletedFromVMSS(backendPoolID, vmSetName string) error {
 	vmssNamesMap := make(map[string]bool)
 
 	// the standard load balancer supports multiple vmss in its backend while the basic sku doesn't
 	if ss.useStandardLoadBalancer() {
-		for _, ipConfigurationID := range ipConfigurationIDs {
-			// in this scenario the vmSetName is an empty string and the name of vmss should be obtained from the provider IDs of nodes
-			vmssName, resourceGroupName, err := getScaleSetAndResourceGroupNameByIPConfigurationID(ipConfigurationID)
+		cachedUniform, err := ss.vmssCache.Get(consts.VMSSKey, azcache.CacheReadTypeDefault)
+		if err != nil {
+			klog.Errorf("ensureBackendPoolDeletedFromVMSS: failed to get vmss uniform from cache: %v", err)
+			return err
+		}
+		vmssUniformMap := cachedUniform.(*sync.Map)
+
+		var errorList []error
+		walk := func(key, value interface{}) bool {
+			var vmss *compute.VirtualMachineScaleSet
+			if vmssEntry, ok := value.(*vmssEntry); ok {
+				vmss = vmssEntry.vmss
+			} else if v, ok := value.(*compute.VirtualMachineScaleSet); ok {
+				vmss = v
+			}
+
+			// When vmss is being deleted, CreateOrUpdate API would report "the vmss is being deleted" error.
+			// Since it is being deleted, we shouldn't send more CreateOrUpdate requests for it.
+			if vmss.ProvisioningState != nil && strings.EqualFold(*vmss.ProvisioningState, consts.VirtualMachineScaleSetsDeallocating) {
+				klog.V(3).Infof("ensureBackendPoolDeletedFromVMSS: found vmss %s being deleted, skipping", to.String(vmss.Name))
+				return true
+			}
+			if vmss.VirtualMachineProfile == nil {
+				klog.V(4).Infof("ensureBackendPoolDeletedFromVMSS: vmss %s has no VirtualMachineProfile, skipping", to.String(vmss.Name))
+				return true
+			}
+			if vmss.VirtualMachineProfile.NetworkProfile.NetworkInterfaceConfigurations == nil {
+				klog.V(4).Infof("ensureBackendPoolDeletedFromVMSS: cannot obtain the primary network interface configuration, of vmss %s", to.String(vmss.Name))
+				return true
+			}
+			vmssNIC := *vmss.VirtualMachineProfile.NetworkProfile.NetworkInterfaceConfigurations
+			primaryNIC, err := getPrimaryNetworkInterfaceConfigurationForScaleSet(vmssNIC, to.String(vmss.Name))
 			if err != nil {
-				klog.V(4).Infof("ensureBackendPoolDeletedFromVMSS: found VMAS ipcConfigurationID %s, will skip checking and continue", ipConfigurationID)
-				continue
+				klog.Errorf("ensureBackendPoolDeletedFromVMSS: failed to get the primary network interface config of the VMSS %s: %v", to.String(vmss.Name), err)
+				errorList = append(errorList, err)
+				return true
 			}
-			// only vmsses in the resource group same as it's in azure config are included
-			if strings.EqualFold(resourceGroupName, ss.ResourceGroup) {
-				vmssNamesMap[vmssName] = true
+			primaryIPConfig, err := getPrimaryIPConfigFromVMSSNetworkConfig(primaryNIC)
+			if err != nil {
+				klog.Errorf("ensureBackendPoolDeletedFromVMSS: failed to the primary IP config from the VMSS %s's network config : %v", to.String(vmss.Name), err)
+				errorList = append(errorList, err)
+				return true
+			}
+			loadBalancerBackendAddressPools := make([]compute.SubResource, 0)
+			if primaryIPConfig.LoadBalancerBackendAddressPools != nil {
+				loadBalancerBackendAddressPools = *primaryIPConfig.LoadBalancerBackendAddressPools
 			}
+			for _, loadBalancerBackendAddressPool := range loadBalancerBackendAddressPools {
+				if strings.EqualFold(to.String(loadBalancerBackendAddressPool.ID), backendPoolID) {
+					klog.V(4).Infof("ensureBackendPoolDeletedFromVMSS: found vmss %s with backend pool %s, removing it", to.String(vmss.Name), backendPoolID)
+					vmssNamesMap[to.String(vmss.Name)] = true
+				}
+			}
+
+			return true
+		}
+
+		// Walk through all cached vmss, and find the vmss that contains the backendPoolID.
+		vmssUniformMap.Range(walk)
+		if len(errorList) > 0 {
+			return utilerrors.Flatten(utilerrors.NewAggregate(errorList))
 		}
 	} else {
 		vmssNamesMap[vmSetName] = true
@@ -1570,7 +1620,7 @@ func (ss *ScaleSet) EnsureBackendPoolDeleted(service *v1.Service, backendPoolID,
 
 	// 1. Ensure the backendPoolID is deleted from the VMSS.
 	if deleteFromVMSet {
-		err := ss.ensureBackendPoolDeletedFromVMSS(service, backendPoolID, vmSetName, ipConfigurationIDs)
+		err := ss.ensureBackendPoolDeletedFromVMSS(backendPoolID, vmSetName)
 		if err != nil {
 			return err
 		}
@@ -1729,23 +1779,23 @@ func (ss *ScaleSet) EnsureBackendPoolDeletedFromVMSets(vmssNamesMap map[string]b
 		// When vmss is being deleted, CreateOrUpdate API would report "the vmss is being deleted" error.
 		// Since it is being deleted, we shouldn't send more CreateOrUpdate requests for it.
 		if vmss.ProvisioningState != nil && strings.EqualFold(*vmss.ProvisioningState, consts.VirtualMachineScaleSetsDeallocating) {
-			klog.V(3).Infof("ensureVMSSInPool: found vmss %s being deleted, skipping", vmssName)
+			klog.V(3).Infof("EnsureBackendPoolDeletedFromVMSets: found vmss %s being deleted, skipping", vmssName)
 			continue
 		}
 		if vmss.VirtualMachineProfile.NetworkProfile.NetworkInterfaceConfigurations == nil {
-			klog.V(4).Infof("EnsureHostInPool: cannot obtain the primary network interface configuration, of vmss %s", vmssName)
+			klog.V(4).Infof("EnsureBackendPoolDeletedFromVMSets: cannot obtain the primary network interface configuration, of vmss %s", vmssName)
 			continue
 		}
 		vmssNIC := *vmss.VirtualMachineProfile.NetworkProfile.NetworkInterfaceConfigurations
 		primaryNIC, err := getPrimaryNetworkInterfaceConfigurationForScaleSet(vmssNIC, vmssName)
 		if err != nil {
-			klog.Errorf("ensureBackendPoolDeletedFromVMSS: failed to get the primary network interface config of the VMSS %s: %v", vmssName, err)
+			klog.Errorf("EnsureBackendPoolDeletedFromVMSets: failed to get the primary network interface config of the VMSS %s: %v", vmssName, err)
 			errors = append(errors, err)
 			continue
 		}
 		primaryIPConfig, err := getPrimaryIPConfigFromVMSSNetworkConfig(primaryNIC)
 		if err != nil {
-			klog.Errorf("ensureBackendPoolDeletedFromVMSS: failed to the primary IP config from the VMSS %s's network config : %v", vmssName, err)
+			klog.Errorf("EnsureBackendPoolDeletedFromVMSets: failed to the primary IP config from the VMSS %s's network config : %v", vmssName, err)
 			errors = append(errors, err)
 			continue
 		}
@@ -1759,7 +1809,7 @@ func (ss *ScaleSet) EnsureBackendPoolDeletedFromVMSets(vmssNamesMap map[string]b
 		for i := len(loadBalancerBackendAddressPools) - 1; i >= 0; i-- {
 			curPool := loadBalancerBackendAddressPools[i]
 			if strings.EqualFold(backendPoolID, *curPool.ID) {
-				klog.V(10).Infof("ensureBackendPoolDeletedFromVMSS gets unwanted backend pool %q for VMSS %s", backendPoolID, vmssName)
+				klog.V(10).Infof("EnsureBackendPoolDeletedFromVMSets gets unwanted backend pool %q for VMSS %s", backendPoolID, vmssName)
 				found = true
 				newBackendPools = append(loadBalancerBackendAddressPools[:i], loadBalancerBackendAddressPools[i+1:]...)
 			}
@@ -1782,10 +1832,10 @@ func (ss *ScaleSet) EnsureBackendPoolDeletedFromVMSets(vmssNamesMap map[string]b
 				},
 			}
 
-			klog.V(2).Infof("ensureBackendPoolDeletedFromVMSS begins to update vmss(%s) with backendPoolID %s", vmssName, backendPoolID)
+			klog.V(2).Infof("EnsureBackendPoolDeletedFromVMSets begins to update vmss(%s) with backendPoolID %s", vmssName, backendPoolID)
 			rerr := ss.CreateOrUpdateVMSS(ss.ResourceGroup, vmssName, newVMSS)
 			if rerr != nil {
-				klog.Errorf("ensureBackendPoolDeletedFromVMSS CreateOrUpdateVMSS(%s) with new backendPoolID %s, err: %v", vmssName, backendPoolID, rerr)
+				klog.Errorf("EnsureBackendPoolDeletedFromVMSets CreateOrUpdateVMSS(%s) with new backendPoolID %s, err: %v", vmssName, backendPoolID, rerr)
 				return rerr.Error()
 			}
 
diff --git a/pkg/provider/azure_vmss_cache.go b/pkg/provider/azure_vmss_cache.go
index 62e4ad831..71dcc70cb 100644
--- a/pkg/provider/azure_vmss_cache.go
+++ b/pkg/provider/azure_vmss_cache.go
@@ -55,7 +55,7 @@ type availabilitySetNodeEntry struct {
 
 func (ss *ScaleSet) newVMSSCache() (*azcache.TimedCache, error) {
 	getter := func(key string) (interface{}, error) {
-		localCache := &sync.Map{} // [vmasName]*vmssEntry
+		localCache := &sync.Map{} // [vmssName]*vmssEntry
 
 		allResourceGroups, err := ss.GetResourceGroups()
 		if err != nil {


Test patch:
diff --git a/pkg/provider/azure_vmss_test.go b/pkg/provider/azure_vmss_test.go
index ea2752273..fb9445713 100644
--- a/pkg/provider/azure_vmss_test.go
+++ b/pkg/provider/azure_vmss_test.go
@@ -2408,42 +2408,38 @@ func TestEnsureBackendPoolDeletedFromVMSS(t *testing.T) {
 	defer ctrl.Finish()
 
 	testCases := []struct {
-		description        string
-		backendPoolID      string
-		ipConfigurationIDs []string
-		isVMSSDeallocating bool
-		isVMSSNilNICConfig bool
-		expectedPutVMSS    bool
-		vmssClientErr      *retry.Error
-		expectedErr        error
+		description                    string
+		backendPoolID                  string
+		ipConfigurationIDs             []string
+		isVMSSDeallocating             bool
+		isVMSSNilNICConfig             bool
+		isVMSSNilVirtualMachineProfile bool
+		expectedPutVMSS                bool
+		vmssClientErr                  *retry.Error
+		expectedErr                    error
 	}{
-		{
-			description:        "ensureBackendPoolDeletedFromVMSS should skip the IP config if it's ID is invalid",
-			ipConfigurationIDs: []string{"invalid/id"},
-		},
 		{
 			description:        "ensureBackendPoolDeletedFromVMSS should skip the VMSS if it's being deleting",
-			ipConfigurationIDs: []string{"/subscriptions/sub/resourceGroups/rg/providers/Microsoft.Compute/virtualMachineScaleSets/vmss/virtualMachines/vmss-vm-000000/networkInterfaces/nic"},
 			isVMSSDeallocating: true,
 		},
 		{
 			description:        "ensureBackendPoolDeletedFromVMSS should skip the VMSS if it's NIC config is nil",
-			ipConfigurationIDs: []string{"/subscriptions/sub/resourceGroups/rg/providers/Microsoft.Compute/virtualMachineScaleSets/vmss/virtualMachines/vmss-vm-000000/networkInterfaces/nic"},
 			isVMSSNilNICConfig: true,
 		},
 		{
-			description:        "ensureBackendPoolDeletedFromVMSS should delete the corresponding LB backendpool ID",
-			ipConfigurationIDs: []string{"/subscriptions/sub/resourceGroups/rg/providers/Microsoft.Compute/virtualMachineScaleSets/vmss/virtualMachines/vmss-vm-000000/networkInterfaces/nic"},
-			backendPoolID:      testLBBackendpoolID0,
-			expectedPutVMSS:    true,
+			description:     "ensureBackendPoolDeletedFromVMSS should delete the corresponding LB backendpool ID",
+			backendPoolID:   testLBBackendpoolID0,
+			expectedPutVMSS: true,
 		},
 		{
-			description:        "ensureBackendPoolDeletedFromVMSS should skip the VMSS if there's no wanted LB backendpool ID",
-			ipConfigurationIDs: []string{"/subscriptions/sub/resourceGroups/rg/providers/Microsoft.Compute/virtualMachineScaleSets/vmss/virtualMachines/vmss-vm-000000/networkInterfaces/nic"},
-			backendPoolID:      testLBBackendpoolID1,
+			description:   "ensureBackendPoolDeletedFromVMSS should skip the VMSS if there's no wanted LB backendpool ID",
+			backendPoolID: testLBBackendpoolID1,
+		},
+		{
+			description:                    "ensureBackendPoolDeletedFromVMSS should skip the VMSS if there's no vm profile",
+			isVMSSNilVirtualMachineProfile: true,
 		},
 		{
-			description:        "ensureBackendPoolDeletedFromVMSS should report the error that occurs during VMSS client's call",
 			ipConfigurationIDs: []string{"/subscriptions/sub/resourceGroups/rg/providers/Microsoft.Compute/virtualMachineScaleSets/vmss/virtualMachines/vmss-vm-000000/networkInterfaces/nic"},
 			backendPoolID:      testLBBackendpoolID0,
 			expectedPutVMSS:    true,
@@ -2465,8 +2461,11 @@ func TestEnsureBackendPoolDeletedFromVMSS(t *testing.T) {
 		if test.isVMSSNilNICConfig {
 			expectedVMSS.VirtualMachineProfile.NetworkProfile.NetworkInterfaceConfigurations = nil
 		}
+		if test.isVMSSNilVirtualMachineProfile {
+			expectedVMSS.VirtualMachineProfile = nil
+		}
 		mockVMSSClient := ss.cloud.VirtualMachineScaleSetsClient.(*mockvmssclient.MockInterface)
-		mockVMSSClient.EXPECT().List(gomock.Any(), ss.ResourceGroup).Return([]compute.VirtualMachineScaleSet{expectedVMSS}, nil).AnyTimes()
+		mockVMSSClient.EXPECT().List(gomock.Any(), ss.ResourceGroup).Return([]compute.VirtualMachineScaleSet{expectedVMSS}, nil)
 		vmssPutTimes := 0
 		if test.expectedPutVMSS {
 			vmssPutTimes = 1
@@ -2478,7 +2477,7 @@ func TestEnsureBackendPoolDeletedFromVMSS(t *testing.T) {
 		mockVMSSVMClient := ss.cloud.VirtualMachineScaleSetVMsClient.(*mockvmssvmclient.MockInterface)
 		mockVMSSVMClient.EXPECT().List(gomock.Any(), ss.ResourceGroup, testVMSSName, gomock.Any()).Return(expectedVMSSVMs, nil).AnyTimes()
 
-		err = ss.ensureBackendPoolDeletedFromVMSS(&v1.Service{}, test.backendPoolID, testVMSSName, test.ipConfigurationIDs)
+		err = ss.ensureBackendPoolDeletedFromVMSS(test.backendPoolID, testVMSSName)
 		if test.expectedErr != nil {
 			assert.EqualError(t, test.expectedErr, err.Error(), test.description+", but an error occurs")
 		}