Allow Requests to be Mirrored to different backends

Add a feature which allows traffic to be mirrored to
additional backends. This is useful for testing how
requests will behave on different "test" backends.

See https://nginx.org/en/docs/http/ngx_http_mirror_module.html

test/e2e/annotations/mirror.go

@@ -0,0 +1,66 @@
+/*
+Copyright 2019 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 annotations
+
+import (
+	"strings"
+
+	. "github.com/onsi/ginkgo"
+
+	"k8s.io/ingress-nginx/test/e2e/framework"
+)
+
+var _ = framework.IngressNginxDescribe("Annotations - Mirror", func() {
+	f := framework.NewDefaultFramework("mirror")
+	host := "mirror.foo.com"
+
+	BeforeEach(func() {
+		f.NewEchoDeployment()
+	})
+
+	AfterEach(func() {
+	})
+
+	It("should set mirror-uri to /mirror", func() {
+		annotations := map[string]string{
+			"nginx.ingress.kubernetes.io/mirror-uri": "/mirror",
+		}
+
+		ing := framework.NewSingleIngress(host, "/", host, f.Namespace, "http-svc", 80, &annotations)
+		f.EnsureIngress(ing)
+
+		f.WaitForNginxServer(host,
+			func(server string) bool {
+				return strings.Contains(server, "mirror /mirror;") && strings.Contains(server, "mirror_request_body on;")
+			})
+	})
+
+	It("should disable mirror-request-body", func() {
+		annotations := map[string]string{
+			"nginx.ingress.kubernetes.io/mirror-uri":          "/mirror",
+			"nginx.ingress.kubernetes.io/mirror-request-body": "off",
+		}
+
+		ing := framework.NewSingleIngress(host, "/", host, f.Namespace, "http-svc", 80, &annotations)
+		f.EnsureIngress(ing)
+
+		f.WaitForNginxServer(host,
+			func(server string) bool {
+				return strings.Contains(server, "mirror /mirror;") && strings.Contains(server, "mirror_request_body off;")
+			})
+	})
+})