Repository: kubernetes-sigs/cloud-provider-azure
Pull request #2426 (2022-09-28 13:39:05)

[release-1.25] Get latest service before UpdateLoadBalancer and serialize LB reconcile
This is an automated cherry-pick of #2406

/assign jwtty

```release-note
Avoid race condition between node-sync-loop routine and service reconcile routine.
Avoid UpdateLoadBalancer() using stale service spec to update Load Balancers.
```


Patch:
diff --git a/pkg/provider/azure.go b/pkg/provider/azure.go
index 3fe132006..dd28ee28a 100644
--- a/pkg/provider/azure.go
+++ b/pkg/provider/azure.go
@@ -38,6 +38,7 @@ import (
 	clientset "k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/kubernetes/scheme"
 	v1core "k8s.io/client-go/kubernetes/typed/core/v1"
+	corelisters "k8s.io/client-go/listers/core/v1"
 	"k8s.io/client-go/tools/cache"
 	"k8s.io/client-go/tools/record"
 	"k8s.io/client-go/util/flowcontrol"
@@ -359,6 +360,11 @@ type Cloud struct {
 	// use LB frontEndIpConfiguration ID as the key and search for PLS attached to the frontEnd
 	plsCache *azcache.TimedCache
 
+	// Add service lister to always get latest service
+	serviceLister corelisters.ServiceLister
+	// node-sync-loop routine and service-reconcile routine should not update LoadBalancer at the same time
+	serviceReconcileLock sync.Mutex
+
 	*ManagedDiskController
 	*controllerCommon
 }
@@ -1061,6 +1067,8 @@ func (az *Cloud) SetInformers(informerFactory informers.SharedInformerFactory) {
 		},
 	})
 	az.nodeInformerSynced = nodeInformer.HasSynced
+
+	az.serviceLister = informerFactory.Core().V1().Services().Lister()
 }
 
 // updateNodeCaches updates local cache for node's zones and external resource groups.
diff --git a/pkg/provider/azure_loadbalancer.go b/pkg/provider/azure_loadbalancer.go
index 706cf31df..4c55c90e6 100644
--- a/pkg/provider/azure_loadbalancer.go
+++ b/pkg/provider/azure_loadbalancer.go
@@ -31,6 +31,7 @@ import (
 	"github.com/Azure/go-autorest/autorest/to"
 
 	v1 "k8s.io/api/core/v1"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	utilerrors "k8s.io/apimachinery/pkg/util/errors"
 	"k8s.io/apimachinery/pkg/util/sets"
 	cloudprovider "k8s.io/cloud-provider"
@@ -144,6 +145,11 @@ func (az *Cloud) EnsureLoadBalancer(ctx context.Context, clusterName string, ser
 	// When a client updates the internal load balancer annotation,
 	// the service may be switched from an internal LB to a public one, or vise versa.
 	// Here we'll firstly ensure service do not lie in the opposite LB.
+
+	// Serialize service reconcile process
+	az.serviceReconcileLock.Lock()
+	defer az.serviceReconcileLock.Unlock()
+
 	var err error
 	serviceName := getServiceName(service)
 	mc := metrics.NewMetricContext("services", "ensure_loadbalancer", az.ResourceGroup, az.getNetworkResourceSubscriptionID(), serviceName)
@@ -164,8 +170,25 @@ func (az *Cloud) EnsureLoadBalancer(ctx context.Context, clusterName string, ser
 	return lbStatus, nil
 }
 
+func (az *Cloud) getLatestService(service *v1.Service) (*v1.Service, bool, error) {
+	latestService, err := az.serviceLister.Services(service.Namespace).Get(service.Name)
+	switch {
+	case apierrors.IsNotFound(err):
+		// service absence in store means the service deletion is caught by watcher
+		return nil, false, nil
+	case err != nil:
+		return nil, false, err
+	default:
+		return latestService.DeepCopy(), true, nil
+	}
+}
+
 // UpdateLoadBalancer updates hosts under the specified load balancer.
 func (az *Cloud) UpdateLoadBalancer(ctx context.Context, clusterName string, service *v1.Service, nodes []*v1.Node) error {
+	// Serialize service reconcile process
+	az.serviceReconcileLock.Lock()
+	defer az.serviceReconcileLock.Unlock()
+
 	var err error
 	serviceName := getServiceName(service)
 	mc := metrics.NewMetricContext("services", "update_loadbalancer", az.ResourceGroup, az.getNetworkResourceSubscriptionID(), serviceName)
@@ -176,6 +199,17 @@ func (az *Cloud) UpdateLoadBalancer(ctx context.Context, clusterName string, ser
 		klog.V(5).InfoS("UpdateLoadBalancer Finish", "service", serviceName, "cluster", clusterName, "service_spec", service, "error", err)
 	}()
 
+	// In case UpdateLoadBalancer gets stale service spec, retrieve the latest from lister
+	service, serviceExists, err := az.getLatestService(service)
+	if err != nil {
+		return fmt.Errorf("UpdateLoadBalancer: failed to get latest service %s: %w", service.Name, err)
+	}
+	if !serviceExists {
+		isOperationSucceeded = true
+		klog.V(2).Infof("UpdateLoadBalancer: skipping service %s because service is going to be deleted", service.Name)
+		return nil
+	}
+
 	shouldUpdateLB, err := az.shouldUpdateLoadBalancer(clusterName, service, nodes)
 	if err != nil {
 		return err
@@ -203,6 +237,10 @@ func (az *Cloud) UpdateLoadBalancer(ctx context.Context, clusterName string, ser
 // have multiple underlying components, meaning a Get could say that the LB
 // doesn't exist even if some part of it is still laying around.
 func (az *Cloud) EnsureLoadBalancerDeleted(ctx context.Context, clusterName string, service *v1.Service) error {
+	// Serialize service reconcile process
+	az.serviceReconcileLock.Lock()
+	defer az.serviceReconcileLock.Unlock()
+
 	var err error
 	isInternal := requiresInternalLoadBalancer(service)
 	serviceName := getServiceName(service)
@@ -2599,7 +2637,7 @@ func (az *Cloud) shouldUpdateLoadBalancer(clusterName string, service *v1.Servic
 	}
 
 	_, _, existsLb, _ := az.getServiceLoadBalancer(service, clusterName, nodes, false, existingManagedLBs)
-	return existsLb && service.ObjectMeta.DeletionTimestamp == nil, nil
+	return existsLb && service.ObjectMeta.DeletionTimestamp == nil && service.Spec.Type == v1.ServiceTypeLoadBalancer, nil
 }
 
 func logSafe(s *string) string {


Test patch:
diff --git a/pkg/provider/azure_loadbalancer_test.go b/pkg/provider/azure_loadbalancer_test.go
index a024c127a..9cb3418c2 100644
--- a/pkg/provider/azure_loadbalancer_test.go
+++ b/pkg/provider/azure_loadbalancer_test.go
@@ -4221,30 +4221,42 @@ func TestShouldUpdateLoadBalancer(t *testing.T) {
 	testCases := []struct {
 		desc                   string
 		lbHasDeletionTimestamp bool
+		serviceType            v1.ServiceType
 		existsLb               bool
 		expectedOutput         bool
 	}{
 		{
 			desc:                   "should update a load balancer that does not have a deletion timestamp and exists in Azure",
 			lbHasDeletionTimestamp: false,
+			serviceType:            v1.ServiceTypeLoadBalancer,
 			existsLb:               true,
 			expectedOutput:         true,
 		},
 		{
 			desc:                   "should not update a load balancer that is being deleted / already deleted in K8s",
 			lbHasDeletionTimestamp: true,
+			serviceType:            v1.ServiceTypeLoadBalancer,
+			existsLb:               true,
+			expectedOutput:         false,
+		},
+		{
+			desc:                   "should not update a load balancer that is no longer LoadBalancer type in K8s",
+			lbHasDeletionTimestamp: false,
+			serviceType:            v1.ServiceTypeClusterIP,
 			existsLb:               true,
 			expectedOutput:         false,
 		},
 		{
 			desc:                   "should not update a load balancer that does not exist in Azure",
 			lbHasDeletionTimestamp: false,
+			serviceType:            v1.ServiceTypeLoadBalancer,
 			existsLb:               false,
 			expectedOutput:         false,
 		},
 		{
 			desc:                   "should not update a load balancer that has a deletion timestamp and does not exist in Azure",
 			lbHasDeletionTimestamp: true,
+			serviceType:            v1.ServiceTypeLoadBalancer,
 			existsLb:               false,
 			expectedOutput:         false,
 		},
@@ -4253,6 +4265,7 @@ func TestShouldUpdateLoadBalancer(t *testing.T) {
 	for i, test := range testCases {
 		az := GetTestCloud(ctrl)
 		service := getTestService("test1", v1.ProtocolTCP, nil, false, 80)
+		service.Spec.Type = test.serviceType
 		setMockPublicIPs(az, ctrl, 1)
 		mockLBsClient := mockloadbalancerclient.NewMockInterface(ctrl)
 		az.LoadBalancerClient = mockLBsClient