/*
Copyright 2017 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package azure

import (
	"errors"
	"fmt"
	"regexp"
	"sort"
	"strconv"
	"strings"

	"github.com/Azure/azure-sdk-for-go/arm/compute"
	"github.com/Azure/azure-sdk-for-go/arm/network"
	"github.com/Azure/go-autorest/autorest/to"
	"github.com/golang/glog"

	"k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/kubernetes/pkg/cloudprovider"
)

var (
	// ErrorNotVmssInstance indicates an instance is not belongint to any vmss.
	ErrorNotVmssInstance = errors.New("not a vmss instance")

	scaleSetNameRE = regexp.MustCompile(`^/subscriptions/(?:.*)/Microsoft.Compute/virtualMachineScaleSets/(.+)/virtualMachines(?:.*)`)
)

// scaleSet implements VMSet interface for Azure scale set.
type scaleSet struct {
	*Cloud

	// availabilitySet is also required for scaleSet because some instances
	// (e.g. master nodes) may not belong to any scale sets.
	availabilitySet VMSet
}

// newScaleSet creates a new scaleSet.
func newScaleSet(az *Cloud) VMSet {
	return &scaleSet{
		Cloud:           az,
		availabilitySet: newAvailabilitySet(az),
	}
}

// GetInstanceIDByNodeName gets the cloud provider ID by node name.
// It must return ("", cloudprovider.InstanceNotFound) if the instance does
// not exist or is no longer running.
func (ss *scaleSet) GetInstanceIDByNodeName(name string) (string, error) {
	instanceID, err := ss.getScaleSetInstanceIDByName(name, ss.PrimaryScaleSetName)
	if err != nil {
		if err == cloudprovider.InstanceNotFound || err == ErrorNotVmssInstance {
			// Retry with standard type because master nodes may not belong to any vmss.
			// TODO: find a better way to identify the type of VM.
			return ss.availabilitySet.GetInstanceIDByNodeName(name)
		}

		return "", err
	}

	return instanceID, nil
}

func (ss *scaleSet) getScaleSetInstanceIDByName(name, scaleSetName string) (string, error) {
	var machine compute.VirtualMachineScaleSetVM
	var exists bool
	var err error

	ss.operationPollRateLimiter.Accept()
	machine, exists, err = ss.getScaleSetVM(name, scaleSetName)
	if err != nil {
		if ss.CloudProviderBackoff {
			glog.V(2).Infof("InstanceID(%s) backing off", name)
			machine, exists, err = ss.GetScaleSetsVMWithRetry(types.NodeName(name), scaleSetName)
			if err != nil {
				glog.V(2).Infof("InstanceID(%s) abort backoff", name)
				return "", err
			}
		} else {
			return "", err
		}
	} else if !exists {
		return "", cloudprovider.InstanceNotFound
	}

	return *machine.ID, nil
}

func (ss *scaleSet) getScaleSetVM(nodeName, scaleSetName string) (vm compute.VirtualMachineScaleSetVM, exists bool, err error) {
	instanceID, err := getScaleSetVMInstanceID(nodeName)
	if err != nil {
		return vm, false, err
	}

	return ss.getScaleSetVMByID(instanceID, scaleSetName)
}

func (ss *scaleSet) getScaleSetVMByID(instanceID, scaleSetName string) (vm compute.VirtualMachineScaleSetVM, exists bool, err error) {
	var realErr error

	// scaleSetName is required to query VM info.
	if scaleSetName == "" {
		scaleSetName = ss.PrimaryScaleSetName
	}

	ss.operationPollRateLimiter.Accept()
	glog.V(10).Infof("VirtualMachineScaleSetVMsClient.Get(%s): start", instanceID)
	vm, err = ss.VirtualMachineScaleSetVMsClient.Get(ss.ResourceGroup, scaleSetName, instanceID)
	glog.V(10).Infof("VirtualMachineScaleSetVMsClient.Get(%s): end", instanceID)

	exists, realErr = checkResourceExistsFromError(err)
	if realErr != nil {
		return vm, false, realErr
	}

	if !exists {
		return vm, false, nil
	}

	return vm, exists, err
}

// GetNodeNameByProviderID gets the node name by provider ID.
func (ss *scaleSet) GetNodeNameByProviderID(providerID string) (types.NodeName, error) {
	// NodeName is not part of providerID for vmss instances.
	parts := strings.Split(providerID, "/")
	instanceID := parts[len(parts)-1]
	machine, exist, err := ss.getScaleSetVMByID(instanceID, ss.PrimaryScaleSetName)
	if !exist {
		return "", cloudprovider.InstanceNotFound
	}
	if err != nil {
		return "", err
	}

	return types.NodeName(*machine.OsProfile.ComputerName), nil
}

// GetInstanceTypeByNodeName gets the instance type by node name.
func (ss *scaleSet) GetInstanceTypeByNodeName(name string) (string, error) {
	instanceType, err := ss.getScaleSetInstanceTypeByNodeName(name)
	if err != nil {
		if err == cloudprovider.InstanceNotFound || err == ErrorNotVmssInstance {
			// Retry with standard type because master nodes may not belong to any vmss.
			// TODO: find a better way to identify the type of VM.
			return ss.availabilitySet.GetInstanceTypeByNodeName(name)
		}

		return "", err
	}

	return instanceType, nil
}

func (ss *scaleSet) getScaleSetInstanceTypeByNodeName(name string) (string, error) {
	machine, exists, err := ss.getScaleSetVM(name, ss.PrimaryScaleSetName)
	if err != nil {
		glog.Errorf("error: ss.getScaleSetInstanceTypeByNodeName(%s), ss.getScaleSetVM(%s) err=%v", name, name, err)
		return "", err
	} else if !exists {
		return "", cloudprovider.InstanceNotFound
	}

	if machine.Sku.Name != nil {
		return *machine.Sku.Name, nil
	}

	return "", fmt.Errorf("instance type is not defined")
}

// GetZoneByNodeName gets cloudprovider.Zone by node name.
func (ss *scaleSet) GetZoneByNodeName(name string) (cloudprovider.Zone, error) {
	instanceID, err := getScaleSetVMInstanceID(name)
	if err != nil {
		if err == ErrorNotVmssInstance {
			// Retry with standard type because master nodes may not belong to any vmss.
			// TODO: find a better way to identify the type of VM.
			return ss.availabilitySet.GetZoneByNodeName(name)
		}
		return cloudprovider.Zone{}, err
	}

	vm, err := ss.VirtualMachineScaleSetVMsClient.Get(ss.ResourceGroup, ss.Config.PrimaryScaleSetName, instanceID)
	if err != nil {
		return cloudprovider.Zone{}, err
	}

	// PlatformFaultDomain is not included in VirtualMachineScaleSetVM, so we get it from VirtualMachineScaleSetVMInstanceView.
	vmView, err := ss.VirtualMachineScaleSetVMsClient.GetInstanceView(ss.ResourceGroup, ss.Config.PrimaryScaleSetName, instanceID)
	if err != nil {
		return cloudprovider.Zone{}, err
	}

	failureDomain := strconv.Itoa(int(*vmView.PlatformFaultDomain))
	zone := cloudprovider.Zone{
		FailureDomain: failureDomain,
		Region:        *(vm.Location),
	}
	return zone, nil
}

// GetPrimaryVMSetName returns the VM set name depending on the configured vmType.
// It returns config.PrimaryScaleSetName for vmss and config.PrimaryAvailabilitySetName for standard vmType.
func (ss *scaleSet) GetPrimaryVMSetName() string {
	return ss.Config.PrimaryScaleSetName
}

// GetIPByNodeName gets machine IP by node name.
func (ss *scaleSet) GetIPByNodeName(nodeName, vmSetName string) (string, error) {
	nic, err := ss.GetPrimaryInterface(nodeName, vmSetName)
	if err != nil {
		glog.Errorf("error: ss.GetIPByNodeName(%s), GetPrimaryInterface(%q, %q), err=%v", nodeName, nodeName, vmSetName, err)
		return "", err
	}

	ipConfig, err := getPrimaryIPConfig(nic)
	if err != nil {
		glog.Errorf("error: ss.GetIPByNodeName(%s), getPrimaryIPConfig(%v), err=%v", nodeName, nic, err)
		return "", err
	}

	targetIP := *ipConfig.PrivateIPAddress
	return targetIP, nil
}

// This returns the full identifier of the primary NIC for the given VM.
func (ss *scaleSet) getPrimaryInterfaceID(machine compute.VirtualMachineScaleSetVM) (string, error) {
	if len(*machine.NetworkProfile.NetworkInterfaces) == 1 {
		return *(*machine.NetworkProfile.NetworkInterfaces)[0].ID, nil
	}

	for _, ref := range *machine.NetworkProfile.NetworkInterfaces {
		if *ref.Primary {
			return *ref.ID, nil
		}
	}

	return "", fmt.Errorf("failed to find a primary nic for the vm. vmname=%q", *machine.Name)
}

// machineName is composed of computerNamePrefix and 36-based instanceID.
// And instanceID part if in fixed length of 6 characters.
// Refer https://msftstack.wordpress.com/2017/05/10/figuring-out-azure-vm-scale-set-machine-names/.
func getScaleSetVMInstanceID(machineName string) (string, error) {
	nameLength := len(machineName)
	if nameLength < 6 {
		return "", ErrorNotVmssInstance
	}

	instanceID, err := strconv.ParseUint(machineName[nameLength-6:], 36, 64)
	if err != nil {
		return "", ErrorNotVmssInstance
	}

	return fmt.Sprintf("%d", instanceID), nil
}

// extractScaleSetNameByVMID extracts the scaleset name by scaleSetVirtualMachine's ID.
func extractScaleSetNameByVMID(vmID string) (string, error) {
	matches := scaleSetNameRE.FindStringSubmatch(vmID)
	if len(matches) != 2 {
		return "", ErrorNotVmssInstance
	}

	return matches[1], nil
}

// listScaleSetsWithRetry lists scale sets with exponential backoff retry.
func (ss *scaleSet) listScaleSetsWithRetry() ([]string, error) {
	var err error
	var result compute.VirtualMachineScaleSetListResult
	allScaleSets := make([]string, 0)

	backoffError := wait.ExponentialBackoff(ss.requestBackoff(), func() (bool, error) {
		ss.operationPollRateLimiter.Accept()
		glog.V(10).Infof("VirtualMachineScaleSetsClient.List start for %v", ss.ResourceGroup)
		result, err = ss.VirtualMachineScaleSetsClient.List(ss.ResourceGroup)
		glog.V(10).Infof("VirtualMachineScaleSetsClient.List end for %v", ss.ResourceGroup)
		if err != nil {
			glog.Errorf("VirtualMachineScaleSetsClient.List for %v failed: %v", ss.ResourceGroup, err)
			return false, err
		}

		return true, nil
	})
	if backoffError != nil {
		return nil, backoffError
	}

	appendResults := (result.Value != nil && len(*result.Value) > 1)
	for appendResults {
		for _, scaleSet := range *result.Value {
			allScaleSets = append(allScaleSets, *scaleSet.Name)
		}
		appendResults = false

		if result.NextLink != nil {
			backoffError := wait.ExponentialBackoff(ss.requestBackoff(), func() (bool, error) {
				ss.operationPollRateLimiter.Accept()
				glog.V(10).Infof("VirtualMachineScaleSetsClient.ListNextResults start for %v", ss.ResourceGroup)
				result, err = ss.VirtualMachineScaleSetsClient.ListNextResults(result)
				glog.V(10).Infof("VirtualMachineScaleSetsClient.ListNextResults end for %v", ss.ResourceGroup)
				if err != nil {
					glog.Errorf("VirtualMachineScaleSetsClient.ListNextResults for %v failed: %v", ss.ResourceGroup, err)
					return false, err
				}

				return true, nil
			})
			if backoffError != nil {
				return nil, backoffError
			}

			appendResults = (result.Value != nil && len(*result.Value) > 1)
		}

	}

	return allScaleSets, nil
}

// listScaleSetVMsWithRetry lists VMs belonging to the specified scale set with exponential backoff retry.
func (ss *scaleSet) listScaleSetVMsWithRetry(scaleSetName string) ([]compute.VirtualMachineScaleSetVM, error) {
	var err error
	var result compute.VirtualMachineScaleSetVMListResult
	allVMs := make([]compute.VirtualMachineScaleSetVM, 0)

	backoffError := wait.ExponentialBackoff(ss.requestBackoff(), func() (bool, error) {
		ss.operationPollRateLimiter.Accept()
		glog.V(10).Infof("VirtualMachineScaleSetVMsClient.List start for %v", scaleSetName)
		result, err = ss.VirtualMachineScaleSetVMsClient.List(ss.ResourceGroup, scaleSetName, "", "", "")
		glog.V(10).Infof("VirtualMachineScaleSetVMsClient.List end for %v", scaleSetName)
		if err != nil {
			glog.Errorf("VirtualMachineScaleSetVMsClient.List for %v failed: %v", scaleSetName, err)
			return false, err
		}

		return true, nil
	})
	if backoffError != nil {
		return nil, backoffError
	}

	appendResults := (result.Value != nil && len(*result.Value) > 1)
	for appendResults {
		allVMs = append(allVMs, *result.Value...)
		appendResults = false

		if result.NextLink != nil {
			backoffError := wait.ExponentialBackoff(ss.requestBackoff(), func() (bool, error) {
				ss.operationPollRateLimiter.Accept()
				glog.V(10).Infof("VirtualMachineScaleSetVMsClient.ListNextResults start for %v", scaleSetName)
				result, err = ss.VirtualMachineScaleSetVMsClient.ListNextResults(result)
				glog.V(10).Infof("VirtualMachineScaleSetVMsClient.ListNextResults end for %v", ss.ResourceGroup)
				if err != nil {
					glog.Errorf("VirtualMachineScaleSetVMsClient.ListNextResults for %v failed: %v", scaleSetName, err)
					return false, err
				}

				return true, nil
			})
			if backoffError != nil {
				return nil, backoffError
			}

			appendResults = (result.Value != nil && len(*result.Value) > 1)
		}

	}

	return allVMs, nil
}

// getAgentPoolAvailabiliySets lists the virtual machines for for the resource group and then builds
// a list of availability sets that match the nodes available to k8s.
func (ss *scaleSet) getAgentPoolScaleSets(nodes []*v1.Node) (*[]string, error) {
	scaleSetNames, err := ss.listScaleSetsWithRetry()
	if err != nil {
		return nil, err
	}

	vmNameToScaleSetName := make(map[string]string, len(scaleSetNames))
	for _, scaleSetName := range scaleSetNames {
		vms, err := ss.listScaleSetVMsWithRetry(scaleSetName)
		if err != nil {
			return nil, err
		}

		for idx := range vms {
			vm := vms[idx]
			if vm.OsProfile != nil || vm.OsProfile.ComputerName != nil {
				vmNameToScaleSetName[*vm.OsProfile.ComputerName] = scaleSetName
			}
		}
	}

	agentPoolScaleSets := &[]string{}
	availableScaleSetNames := sets.NewString()
	for nx := range nodes {
		if isMasterNode(nodes[nx]) {
			continue
		}

		nodeName := nodes[nx].Name
		ssName, ok := vmNameToScaleSetName[nodeName]
		if !ok {
			// TODO: support master nodes not managed by VMSS.
			glog.Errorf("Node %q is not belonging to any known scale sets", nodeName)
			return nil, fmt.Errorf("node %q is not belonging to any known scale sets", nodeName)
		}

		if availableScaleSetNames.Has(ssName) {
			continue
		}

		*agentPoolScaleSets = append(*agentPoolScaleSets, ssName)
	}

	return agentPoolScaleSets, nil
}

// GetVMSetNames selects all possible availability sets or scale sets
// (depending vmType configured) for service load balancer. If the service has
// no loadbalancer mode annotaion returns the primary VMSet. If service annotation
// for loadbalancer exists then return the eligible VMSet.
func (ss *scaleSet) GetVMSetNames(service *v1.Service, nodes []*v1.Node) (vmSetNames *[]string, err error) {
	hasMode, isAuto, serviceVMSetNames := getServiceLoadBalancerMode(service)
	if !hasMode {
		// no mode specified in service annotation default to PrimaryScaleSetName.
		scaleSetNames := &[]string{ss.Config.PrimaryScaleSetName}
		return scaleSetNames, nil
	}

	scaleSetNames, err := ss.getAgentPoolScaleSets(nodes)
	if err != nil {
		glog.Errorf("ss.GetVMSetNames - getAgentPoolScaleSets failed err=(%v)", err)
		return nil, err
	}
	if len(*scaleSetNames) == 0 {
		glog.Errorf("ss.GetVMSetNames - No scale sets found for nodes in the cluster, node count(%d)", len(nodes))
		return nil, fmt.Errorf("No scale sets found for nodes, node count(%d)", len(nodes))
	}

	// sort the list to have deterministic selection
	sort.Strings(*scaleSetNames)

	if !isAuto {
		if serviceVMSetNames == nil || len(serviceVMSetNames) == 0 {
			return nil, fmt.Errorf("service annotation for LoadBalancerMode is empty, it should have __auto__ or availability sets value")
		}
		// validate scale set exists
		var found bool
		for sasx := range serviceVMSetNames {
			for asx := range *scaleSetNames {
				if strings.EqualFold((*scaleSetNames)[asx], serviceVMSetNames[sasx]) {
					found = true
					serviceVMSetNames[sasx] = (*scaleSetNames)[asx]
					break
				}
			}
			if !found {
				glog.Errorf("ss.GetVMSetNames - scale set (%s) in service annotation not found", serviceVMSetNames[sasx])
				return nil, fmt.Errorf("scale set (%s) - not found", serviceVMSetNames[sasx])
			}
		}
		vmSetNames = &serviceVMSetNames
	}

	return vmSetNames, nil
}

// GetPrimaryInterface gets machine primary network interface by node name and vmSet.
func (ss *scaleSet) GetPrimaryInterface(nodeName, vmSetName string) (network.Interface, error) {
	ss.operationPollRateLimiter.Accept()
	machine, exists, err := ss.getScaleSetVM(nodeName, vmSetName)
	if !exists || err == cloudprovider.InstanceNotFound || err == ErrorNotVmssInstance {
		// Retry with standard type because master nodes may not belong to any vmss.
		// TODO: find a better way to identify the type of VM.
		return ss.availabilitySet.GetPrimaryInterface(nodeName, "")
	}
	if err != nil {
		glog.Errorf("error: ss.GetPrimaryInterface(%s), ss.getScaleSetVM(%s), err=%v", nodeName, nodeName, err)
		return network.Interface{}, err
	}

	nicID, err := ss.getPrimaryInterfaceID(machine)
	if err != nil {
		glog.Errorf("error: ss.GetPrimaryInterface(%s), getPrimaryInterfaceID(%v), err=%v", nodeName, machine, err)
		return network.Interface{}, err
	}

	nicName, err := getLastSegment(nicID)
	if err != nil {
		glog.Errorf("error: ss.GetPrimaryInterface(%s), getLastSegment(%s), err=%v", nodeName, nicID, err)
		return network.Interface{}, err
	}

	ss.operationPollRateLimiter.Accept()
	glog.V(10).Infof("InterfacesClient.Get(%q): start", nicName)
	nic, err := ss.InterfacesClient.GetVirtualMachineScaleSetNetworkInterface(ss.ResourceGroup, ss.Config.PrimaryScaleSetName, *machine.InstanceID, nicName, "")
	glog.V(10).Infof("InterfacesClient.Get(%q): end", nicName)
	if err != nil {
		glog.Errorf("error: ss.GetPrimaryInterface(%s), ss.GetVirtualMachineScaleSetNetworkInterface.Get(%s, %s, %s), err=%v", nodeName, ss.ResourceGroup, nicName, "", err)
		return network.Interface{}, err
	}

	// Fix interface's location, which is required when updating the interface.
	// TODO: is this a bug of azure SDK?
	if nic.Location == nil || *nic.Location == "" {
		nic.Location = &ss.Config.Location
	}

	return nic, nil
}

// getScaleSet gets a scale set by name.
func (ss *scaleSet) getScaleSet(name string) (compute.VirtualMachineScaleSet, bool, error) {
	ss.operationPollRateLimiter.Accept()
	glog.V(10).Infof("VirtualMachineScaleSetsClient.Get(%s): start", name)
	result, err := ss.VirtualMachineScaleSetsClient.Get(ss.ResourceGroup, name)
	glog.V(10).Infof("VirtualMachineScaleSetsClient.Get(%s): end", name)

	exists, realErr := checkResourceExistsFromError(err)
	if realErr != nil {
		return result, false, realErr
	}

	if !exists {
		return result, false, nil
	}

	return result, exists, err
}

// getScaleSetWithRetry gets scale set with exponential backoff retry
func (ss *scaleSet) getScaleSetWithRetry(name string) (compute.VirtualMachineScaleSet, bool, error) {
	var result compute.VirtualMachineScaleSet
	var exists bool

	err := wait.ExponentialBackoff(ss.requestBackoff(), func() (bool, error) {
		var retryErr error
		result, exists, retryErr = ss.getScaleSet(name)
		if retryErr != nil {
			glog.Errorf("backoff: failure, will retry,err=%v", retryErr)
			return false, nil
		}
		glog.V(2).Infof("backoff: success")
		return true, nil
	})

	return result, exists, err
}

// getPrimaryNetworkConfiguration gets primary network interface configuration for scale sets.
func (ss *scaleSet) getPrimaryNetworkConfiguration(networkConfigurationList *[]compute.VirtualMachineScaleSetNetworkConfiguration, scaleSetName string) (*compute.VirtualMachineScaleSetNetworkConfiguration, error) {
	networkConfigurations := *networkConfigurationList
	if len(networkConfigurations) == 1 {
		return &networkConfigurations[0], nil
	}

	for idx := range networkConfigurations {
		networkConfig := &networkConfigurations[idx]
		if networkConfig.Primary != nil && *networkConfig.Primary == true {
			return networkConfig, nil
		}
	}

	return nil, fmt.Errorf("failed to find a primary network configuration for the scale set %q", scaleSetName)
}

func (ss *scaleSet) getPrimaryIPConfigForScaleSet(config *compute.VirtualMachineScaleSetNetworkConfiguration, scaleSetName string) (*compute.VirtualMachineScaleSetIPConfiguration, error) {
	ipConfigurations := *config.IPConfigurations
	if len(ipConfigurations) == 1 {
		return &ipConfigurations[0], nil
	}

	for idx := range ipConfigurations {
		ipConfig := &ipConfigurations[idx]
		if ipConfig.Primary != nil && *ipConfig.Primary == true {
			return ipConfig, nil
		}
	}

	return nil, fmt.Errorf("failed to find a primary IP configuration for the scale set %q", scaleSetName)
}

// createOrUpdateVMSSWithRetry invokes ss.VirtualMachineScaleSetsClient.CreateOrUpdate with exponential backoff retry.
func (ss *scaleSet) createOrUpdateVMSSWithRetry(virtualMachineScaleSet compute.VirtualMachineScaleSet) error {
	return wait.ExponentialBackoff(ss.requestBackoff(), func() (bool, error) {
		ss.operationPollRateLimiter.Accept()
		glog.V(10).Infof("VirtualMachineScaleSetsClient.CreateOrUpdate(%s): start", *virtualMachineScaleSet.Name)
		respChan, errChan := ss.VirtualMachineScaleSetsClient.CreateOrUpdate(ss.ResourceGroup, *virtualMachineScaleSet.Name, virtualMachineScaleSet, nil)
		resp := <-respChan
		err := <-errChan
		glog.V(10).Infof("VirtualMachineScaleSetsClient.CreateOrUpdate(%s): end", *virtualMachineScaleSet.Name)
		return processRetryResponse(resp.Response, err)
	})
}

// updateVMSSInstancesWithRetry invokes ss.VirtualMachineScaleSetsClient.UpdateInstances with exponential backoff retry.
func (ss *scaleSet) updateVMSSInstancesWithRetry(scaleSetName string, vmInstanceIDs compute.VirtualMachineScaleSetVMInstanceRequiredIDs) error {
	return wait.ExponentialBackoff(ss.requestBackoff(), func() (bool, error) {
		ss.operationPollRateLimiter.Accept()
		glog.V(10).Infof("VirtualMachineScaleSetsClient.UpdateInstances(%s): start", scaleSetName)
		respChan, errChan := ss.VirtualMachineScaleSetsClient.UpdateInstances(ss.ResourceGroup, scaleSetName, vmInstanceIDs, nil)
		resp := <-respChan
		err := <-errChan
		glog.V(10).Infof("VirtualMachineScaleSetsClient.UpdateInstances(%s): end", scaleSetName)
		return processRetryResponse(resp.Response, err)
	})
}

// EnsureHostsInPool ensures the given Node's primary IP configurations are
// participating in the specified LoadBalancer Backend Pool.
func (ss *scaleSet) EnsureHostsInPool(serviceName string, nodes []*v1.Node, backendPoolID string, vmSetName string) error {
	virtualMachineScaleSet, exists, err := ss.getScaleSetWithRetry(vmSetName)
	if err != nil {
		glog.Errorf("ss.getScaleSetWithRetry(%s) for service %q failed: %v", vmSetName, serviceName, err)
		return err
	}
	if !exists {
		errorMessage := fmt.Errorf("Scale set %q not found", vmSetName)
		glog.Errorf("%v", errorMessage)
		return errorMessage
	}

	// Find primary network interface configuration.
	networkConfigureList := virtualMachineScaleSet.VirtualMachineProfile.NetworkProfile.NetworkInterfaceConfigurations
	primaryNetworkConfiguration, err := ss.getPrimaryNetworkConfiguration(networkConfigureList, vmSetName)
	if err != nil {
		return err
	}

	// Find primary IP configuration.
	primaryIPConfiguration, err := ss.getPrimaryIPConfigForScaleSet(primaryNetworkConfiguration, vmSetName)
	if err != nil {
		return err
	}

	// Update primary IP configuration's LoadBalancerBackendAddressPools.
	foundPool := false
	newBackendPools := []compute.SubResource{}
	if primaryIPConfiguration.LoadBalancerBackendAddressPools != nil {
		newBackendPools = *primaryIPConfiguration.LoadBalancerBackendAddressPools
	}
	for _, existingPool := range newBackendPools {
		if strings.EqualFold(backendPoolID, *existingPool.ID) {
			foundPool = true
			break
		}
	}
	if !foundPool {
		newBackendPools = append(newBackendPools,
			compute.SubResource{
				ID: to.StringPtr(backendPoolID),
			})
		primaryIPConfiguration.LoadBalancerBackendAddressPools = &newBackendPools

		glog.V(3).Infof("VirtualMachineScaleSetsClient.CreateOrUpdate for service (%s): scale set (%s) - updating", serviceName, vmSetName)
		ss.operationPollRateLimiter.Accept()
		glog.V(10).Infof("VirtualMachineScaleSetsClient.CreateOrUpdate(%q): start", vmSetName)
		respChan, errChan := ss.VirtualMachineScaleSetsClient.CreateOrUpdate(ss.ResourceGroup, vmSetName, virtualMachineScaleSet, nil)
		resp := <-respChan
		err := <-errChan
		glog.V(10).Infof("VirtualMachineScaleSetsClient.CreateOrUpdate(%q): end", vmSetName)
		if ss.CloudProviderBackoff && shouldRetryAPIRequest(resp.Response, err) {
			glog.V(2).Infof("VirtualMachineScaleSetsClient.CreateOrUpdate for service (%): scale set (%s) - updating, err=%v", serviceName, vmSetName, err)
			retryErr := ss.createOrUpdateVMSSWithRetry(virtualMachineScaleSet)
			if retryErr != nil {
				err = retryErr
				glog.V(2).Infof("VirtualMachineScaleSetsClient.CreateOrUpdate for service (%) abort backoff: scale set (%s) - updating", serviceName, vmSetName)
			}
		}
		if err != nil {
			return err
		}
	}

	// Construct instanceIDs from nodes.
	instanceIDs := []string{}
	for _, curNode := range nodes {
		curScaleSetName, err := extractScaleSetNameByVMID(curNode.Spec.ExternalID)
		if err != nil {
			glog.V(2).Infof("Node %q is not belonging to any scale sets, omitting it", curNode.Name)
			continue
		}
		if curScaleSetName != vmSetName {
			glog.V(2).Infof("Node %q is not belonging to scale set %q, omitting it", curNode.Name, vmSetName)
			continue
		}

		instanceID, err := getLastSegment(curNode.Spec.ExternalID)
		if err != nil {
			glog.Errorf("Failed to get last segment from %q: %v", curNode.Spec.ExternalID, err)
			return err
		}

		instanceIDs = append(instanceIDs, instanceID)
	}

	// Update instances to latest VMSS model.
	vmInstanceIDs := compute.VirtualMachineScaleSetVMInstanceRequiredIDs{
		InstanceIds: &instanceIDs,
	}
	ss.operationPollRateLimiter.Accept()
	glog.V(10).Infof("VirtualMachineScaleSetsClient.UpdateInstances(%q): start", vmSetName)
	respChan, errChan := ss.VirtualMachineScaleSetsClient.UpdateInstances(ss.ResourceGroup, vmSetName, vmInstanceIDs, nil)
	resp := <-respChan
	err = <-errChan
	glog.V(10).Infof("VirtualMachineScaleSetsClient.UpdateInstances(%q): end", vmSetName)
	if ss.CloudProviderBackoff && shouldRetryAPIRequest(resp.Response, err) {
		glog.V(2).Infof("VirtualMachineScaleSetsClient.UpdateInstances for service (%): scale set (%s) - updating, err=%v", serviceName, vmSetName, err)
		retryErr := ss.updateVMSSInstancesWithRetry(vmSetName, vmInstanceIDs)
		if retryErr != nil {
			err = retryErr
			glog.V(2).Infof("VirtualMachineScaleSetsClient.UpdateInstances for service (%) abort backoff: scale set (%s) - updating", serviceName, vmSetName)
		}
	}
	if err != nil {
		return err
	}

	return nil
}

// EnsureBackendPoolDeleted ensures the loadBalancer backendAddressPools deleted from the specified vmSet.
func (ss *scaleSet) EnsureBackendPoolDeleted(poolID, vmSetName string) error {
	virtualMachineScaleSet, exists, err := ss.getScaleSetWithRetry(vmSetName)
	if err != nil {
		glog.Errorf("ss.EnsureBackendPoolDeleted(%s, %s) getScaleSetWithRetry(%s) failed: %v", poolID, vmSetName, vmSetName, err)
		return err
	}
	if !exists {
		glog.V(2).Infof("ss.EnsureBackendPoolDeleted(%s, %s), scale set %s has already been non-exist", poolID, vmSetName, vmSetName)
		return nil
	}

	// Find primary network interface configuration.
	networkConfigureList := virtualMachineScaleSet.VirtualMachineProfile.NetworkProfile.NetworkInterfaceConfigurations
	primaryNetworkConfiguration, err := ss.getPrimaryNetworkConfiguration(networkConfigureList, vmSetName)
	if err != nil {
		return err
	}

	// Find primary IP configuration.
	primaryIPConfiguration, err := ss.getPrimaryIPConfigForScaleSet(primaryNetworkConfiguration, vmSetName)
	if err != nil {
		return err
	}

	// Construct new loadBalancerBackendAddressPools and remove backendAddressPools from primary IP configuration.
	if primaryIPConfiguration.LoadBalancerBackendAddressPools == nil || len(*primaryIPConfiguration.LoadBalancerBackendAddressPools) == 0 {
		return nil
	}
	existingBackendPools := *primaryIPConfiguration.LoadBalancerBackendAddressPools
	newBackendPools := []compute.SubResource{}
	foundPool := false
	for i := len(existingBackendPools) - 1; i >= 0; i-- {
		curPool := existingBackendPools[i]
		if strings.EqualFold(poolID, *curPool.ID) {
			glog.V(10).Infof("EnsureBackendPoolDeleted gets unwanted backend pool %q for scale set %q", poolID, vmSetName)
			foundPool = true
			newBackendPools = append(existingBackendPools[:i], existingBackendPools[i+1:]...)
		}
	}
	if !foundPool {
		// Pool not found, assume it has been already removed.
		return nil
	}

	// Update scale set with backoff.
	primaryIPConfiguration.LoadBalancerBackendAddressPools = &newBackendPools
	glog.V(3).Infof("VirtualMachineScaleSetsClient.CreateOrUpdate: scale set (%s) - updating", vmSetName)
	ss.operationPollRateLimiter.Accept()
	glog.V(10).Infof("VirtualMachineScaleSetsClient.CreateOrUpdate(%q): start", vmSetName)
	respChan, errChan := ss.VirtualMachineScaleSetsClient.CreateOrUpdate(ss.ResourceGroup, vmSetName, virtualMachineScaleSet, nil)
	resp := <-respChan
	err = <-errChan
	glog.V(10).Infof("VirtualMachineScaleSetsClient.CreateOrUpdate(%q): end", vmSetName)
	if ss.CloudProviderBackoff && shouldRetryAPIRequest(resp.Response, err) {
		glog.V(2).Infof("VirtualMachineScaleSetsClient.CreateOrUpdate: scale set (%s) - updating, err=%v", vmSetName, err)
		retryErr := ss.createOrUpdateVMSSWithRetry(virtualMachineScaleSet)
		if retryErr != nil {
			err = retryErr
			glog.V(2).Infof("VirtualMachineScaleSetsClient.CreateOrUpdate abort backoff: scale set (%s) - updating", vmSetName)
		}
	}
	if err != nil {
		return err
	}

	// Update instances to latest VMSS model.
	instanceIDs := []string{"*"}
	vmInstanceIDs := compute.VirtualMachineScaleSetVMInstanceRequiredIDs{
		InstanceIds: &instanceIDs,
	}
	ss.operationPollRateLimiter.Accept()
	glog.V(10).Infof("VirtualMachineScaleSetsClient.UpdateInstances(%q): start", vmSetName)
	updateRespChan, errChan := ss.VirtualMachineScaleSetsClient.UpdateInstances(ss.ResourceGroup, vmSetName, vmInstanceIDs, nil)
	updateResp := <-updateRespChan
	err = <-errChan
	glog.V(10).Infof("VirtualMachineScaleSetsClient.UpdateInstances(%q): end", vmSetName)
	if ss.CloudProviderBackoff && shouldRetryAPIRequest(updateResp.Response, err) {
		glog.V(2).Infof("VirtualMachineScaleSetsClient.UpdateInstances scale set (%s) - updating, err=%v", vmSetName, err)
		retryErr := ss.updateVMSSInstancesWithRetry(vmSetName, vmInstanceIDs)
		if retryErr != nil {
			err = retryErr
			glog.V(2).Infof("VirtualMachineScaleSetsClient.UpdateInstances abort backoff: scale set (%s) - updating", vmSetName)
		}
	}
	if err != nil {
		return err
	}

	return nil
}