Add retries for dns in tcp e2e test (#5283)

test/e2e/tcpudp/tcp.go

@@ -22,12 +22,14 @@ import (
 	"net"
 	"net/http"
 	"strings"
+	"time"
 
 	"github.com/onsi/ginkgo"
 	"github.com/stretchr/testify/assert"
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/util/intstr"
+	"k8s.io/apimachinery/pkg/util/wait"
 
 	"k8s.io/ingress-nginx/test/e2e/framework"
 )
@@ -170,7 +172,30 @@ var _ = framework.IngressNginxDescribe("[TCP] tcp-services", func() {
 				return d.DialContext(ctx, "tcp", fmt.Sprintf("%v:5353", ip))
 			},
 		}
-		ips, err := resolver.LookupHost(context.Background(), "google-public-dns-b.google.com")
+
+		// add retries to LookupHost to avoid random e2e errors
+		retry := wait.Backoff{
+			Steps:    10,
+			Duration: 2 * time.Second,
+			Factor:   0.8,
+			Jitter:   0.2,
+		}
+
+		var ips []string
+		var retryErr error
+		err = wait.ExponentialBackoff(retry, func() (bool, error) {
+			ips, retryErr = resolver.LookupHost(context.Background(), "google-public-dns-b.google.com")
+			if retryErr == nil {
+				return true, nil
+			}
+
+			return false, nil
+		})
+
+		if err == wait.ErrWaitTimeout {
+			err = retryErr
+		}
+
 		assert.Nil(ginkgo.GinkgoT(), err, "unexpected error from DNS resolver")
 		assert.Contains(ginkgo.GinkgoT(), ips, "8.8.4.4")
 	})