Add etag for NSG updates so as to fix nsg race condition

staging/src/k8s.io/legacy-cloud-providers/azure/azure_backoff.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/Azure/azure-sdk-for-go/services/compute/mgmt/2019-03-01/compute"
 	"github.com/Azure/azure-sdk-for-go/services/network/mgmt/2017-09-01/network"
+	"github.com/Azure/go-autorest/autorest/to"
 
 	"k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/runtime"
@@ -146,7 +147,7 @@ func (az *Cloud) CreateOrUpdateSecurityGroup(service *v1.Service, sg network.Sec
 		ctx, cancel := getContextWithCancel()
 		defer cancel()
 
-		resp, err := az.SecurityGroupsClient.CreateOrUpdate(ctx, az.ResourceGroup, *sg.Name, sg)
+		resp, err := az.SecurityGroupsClient.CreateOrUpdate(ctx, az.ResourceGroup, *sg.Name, sg, to.String(sg.Etag))
 		klog.V(10).Infof("SecurityGroupsClient.CreateOrUpdate(%s): end", *sg.Name)
 		if err == nil {
 			if isSuccessHTTPResponse(resp) {
@@ -156,6 +157,11 @@ func (az *Cloud) CreateOrUpdateSecurityGroup(service *v1.Service, sg network.Sec
 				return fmt.Errorf("HTTP response %q", resp.Status)
 			}
 		}
+
+		// Invalidate the cache because ETAG precondition mismatch.
+		if resp != nil && resp.StatusCode == http.StatusPreconditionFailed {
+			az.nsgCache.Delete(*sg.Name)
+		}
 		return err
 	}
 
@@ -168,14 +174,20 @@ func (az *Cloud) CreateOrUpdateSGWithRetry(service *v1.Service, sg network.Secur
 		ctx, cancel := getContextWithCancel()
 		defer cancel()
 
-		resp, err := az.SecurityGroupsClient.CreateOrUpdate(ctx, az.ResourceGroup, *sg.Name, sg)
+		resp, err := az.SecurityGroupsClient.CreateOrUpdate(ctx, az.ResourceGroup, *sg.Name, sg, to.String(sg.Etag))
 		klog.V(10).Infof("SecurityGroupsClient.CreateOrUpdate(%s): end", *sg.Name)
-		done, err := az.processHTTPRetryResponse(service, "CreateOrUpdateSecurityGroup", resp, err)
+		done, retryError := az.processHTTPRetryResponse(service, "CreateOrUpdateSecurityGroup", resp, err)
 		if done && err == nil {
 			// Invalidate the cache right after updating
 			az.nsgCache.Delete(*sg.Name)
 		}
-		return done, err
+
+		// Invalidate the cache and abort backoff because ETAG precondition mismatch.
+		if resp != nil && resp.StatusCode == http.StatusPreconditionFailed {
+			az.nsgCache.Delete(*sg.Name)
+			return true, err
+		}
+		return done, retryError
 	})
 }
 
@@ -538,17 +550,22 @@ func isSuccessHTTPResponse(resp *http.Response) bool {
 }
 
 func shouldRetryHTTPRequest(resp *http.Response, err error) bool {
-	if err != nil {
+	if resp != nil {
-		return true
+		// HTTP 412 (StatusPreconditionFailed) means etag mismatch, hence we shouldn't retry.
+		if resp.StatusCode == http.StatusPreconditionFailed {
+			return false
 		}
 
-	if resp != nil {
+		// HTTP 4xx (except 412) or 5xx suggests we should retry.
-		// HTTP 4xx or 5xx suggests we should retry
 		if 399 < resp.StatusCode && resp.StatusCode < 600 {
 			return true
 		}
 	}
 
+	if err != nil {
+		return true
+	}
+
 	return false
 }
 

staging/src/k8s.io/legacy-cloud-providers/azure/azure_client.go

@@ -81,7 +81,7 @@ type SubnetsClient interface {
 
 // SecurityGroupsClient defines needed functions for azure network.SecurityGroupsClient
 type SecurityGroupsClient interface {
-	CreateOrUpdate(ctx context.Context, resourceGroupName string, networkSecurityGroupName string, parameters network.SecurityGroup) (resp *http.Response, err error)
+	CreateOrUpdate(ctx context.Context, resourceGroupName string, networkSecurityGroupName string, parameters network.SecurityGroup, etag string) (resp *http.Response, err error)
 	Delete(ctx context.Context, resourceGroupName string, networkSecurityGroupName string) (resp *http.Response, err error)
 	Get(ctx context.Context, resourceGroupName string, networkSecurityGroupName string, expand string) (result network.SecurityGroup, err error)
 	List(ctx context.Context, resourceGroupName string) (result []network.SecurityGroup, err error)
@@ -714,7 +714,7 @@ func newAzSecurityGroupsClient(config *azClientConfig) *azSecurityGroupsClient {
 	}
 }
 
-func (az *azSecurityGroupsClient) CreateOrUpdate(ctx context.Context, resourceGroupName string, networkSecurityGroupName string, parameters network.SecurityGroup) (resp *http.Response, err error) {
+func (az *azSecurityGroupsClient) CreateOrUpdate(ctx context.Context, resourceGroupName string, networkSecurityGroupName string, parameters network.SecurityGroup, etag string) (resp *http.Response, err error) {
 	/* Write rate limiting */
 	if !az.rateLimiterWriter.TryAccept() {
 		err = createRateLimitErr(true, "NSGCreateOrUpdate")
@@ -727,7 +727,13 @@ func (az *azSecurityGroupsClient) CreateOrUpdate(ctx context.Context, resourceGr
 	}()
 
 	mc := newMetricContext("security_groups", "create_or_update", resourceGroupName, az.client.SubscriptionID)
-	future, err := az.client.CreateOrUpdate(ctx, resourceGroupName, networkSecurityGroupName, parameters)
+	req, err := az.createOrUpdatePreparer(ctx, resourceGroupName, networkSecurityGroupName, parameters, etag)
+	if err != nil {
+		mc.Observe(err)
+		return nil, err
+	}
+
+	future, err := az.client.CreateOrUpdateSender(req)
 	if err != nil {
 		mc.Observe(err)
 		return future.Response(), err
@@ -738,6 +744,34 @@ func (az *azSecurityGroupsClient) CreateOrUpdate(ctx context.Context, resourceGr
 	return future.Response(), err
 }
 
+// createOrUpdatePreparer prepares the CreateOrUpdate request.
+func (az *azSecurityGroupsClient) createOrUpdatePreparer(ctx context.Context, resourceGroupName string, networkSecurityGroupName string, parameters network.SecurityGroup, etag string) (*http.Request, error) {
+	pathParameters := map[string]interface{}{
+		"networkSecurityGroupName": autorest.Encode("path", networkSecurityGroupName),
+		"resourceGroupName":        autorest.Encode("path", resourceGroupName),
+		"subscriptionId":           autorest.Encode("path", az.client.SubscriptionID),
+	}
+
+	const APIVersion = "2017-09-01"
+	queryParameters := map[string]interface{}{
+		"api-version": APIVersion,
+	}
+
+	preparerDecorators := []autorest.PrepareDecorator{
+		autorest.AsContentType("application/json; charset=utf-8"),
+		autorest.AsPut(),
+		autorest.WithBaseURL(az.client.BaseURI),
+		autorest.WithPathParameters("/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Network/networkSecurityGroups/{networkSecurityGroupName}", pathParameters),
+		autorest.WithJSON(parameters),
+		autorest.WithQueryParameters(queryParameters),
+	}
+	if etag != "" {
+		preparerDecorators = append(preparerDecorators, autorest.WithHeader("If-Match", autorest.String(etag)))
+	}
+	preparer := autorest.CreatePreparer(preparerDecorators...)
+	return preparer.Prepare((&http.Request{}).WithContext(ctx))
+}
+
 func (az *azSecurityGroupsClient) Delete(ctx context.Context, resourceGroupName string, networkSecurityGroupName string) (resp *http.Response, err error) {
 	/* Write rate limiting */
 	if !az.rateLimiterWriter.TryAccept() {