test: IngressClass exclusion test races with admission cache

The admission cache may take longer to see both ingress classes
than it takes to create the ingress. We must loop until we see
the appropriate error, cleaning up after ourselves as we go.

test/e2e/network/ingressclass.go

@@ -19,10 +19,12 @@ package network
 import (
 	"context"
 	"strings"
+	"time"
 
 	networkingv1beta1 "k8s.io/api/networking/v1beta1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/util/intstr"
+	"k8s.io/apimachinery/pkg/util/wait"
 	clientset "k8s.io/client-go/kubernetes"
 	"k8s.io/kubernetes/test/e2e/framework"
 
@@ -73,14 +75,19 @@ var _ = SIGDescribe("IngressClass [Feature:Ingress]", func() {
 		framework.ExpectNoError(err)
 		defer deleteIngressClass(cs, ingressClass2.Name)
 
-		_, err = createBasicIngress(cs, f.Namespace.Name)
+		// the admission controller may take a few seconds to observe both ingress classes
-		if err == nil {
-			framework.Failf("Expected error creating Ingress")
-		}
-
 		expectedErr := "2 default IngressClasses were found, only 1 allowed"
-		if !strings.Contains(err.Error(), expectedErr) {
+		var lastErr error
-			framework.Failf("Expected error to contain %s, got %s", expectedErr, err.Error())
+		if err := wait.Poll(time.Second, time.Minute, func() (bool, error) {
+			defer cs.NetworkingV1beta1().Ingresses(f.Namespace.Name).Delete(context.TODO(), "ingress1", metav1.DeleteOptions{})
+			_, err := createBasicIngress(cs, f.Namespace.Name)
+			if err == nil {
+				return false, nil
+			}
+			lastErr = err
+			return strings.Contains(err.Error(), expectedErr), nil
+		}); err != nil {
+			framework.Failf("Expected error to contain %s, got %s", expectedErr, lastErr.Error())
 		}
 	})