Add app-root annotation support for kubernetes ingress

docs/configuration/backends/kubernetes.md

@@ -127,6 +127,7 @@ The following general annotations are applicable on the Ingress object:
 | `traefik.ingress.kubernetes.io/rewrite-target: /users`                          | Replaces each matched Ingress path with the specified one, and adds the old path to the `X-Replaced-Path` header.                               |
 | `traefik.ingress.kubernetes.io/rule-type: PathPrefixStrip`                      | Override the default frontend rule type. Default: `PathPrefix`.                                                                                 |
 | `traefik.ingress.kubernetes.io/whitelist-source-range: "1.2.3.0/24, fe80::/16"` | A comma-separated list of IP ranges permitted for access. all source IPs are permitted if the list is empty or a single range is ill-formatted. |
+| `traefik.ingress.kubernetes.io/app-root: "/index.html"` | Redirects all requests for `/` to the defined path. Non-root paths will not be affected by this annotation and handled normally. This annotation may not be combined with the `ReplacePath` rule type or any other annotation leveraging that rule type. Trying to do so leads to an error and the corresponding Ingress object being ignored. |
 
 <1> `traefik.ingress.kubernetes.io/error-pages` example:
 

provider/kubernetes/annotations.go

@@ -29,6 +29,7 @@ const (
 	annotationKubernetesRateLimit                = "ingress.kubernetes.io/rate-limit"
 	annotationKubernetesErrorPages               = "ingress.kubernetes.io/error-pages"
 	annotationKubernetesBuffering                = "ingress.kubernetes.io/buffering"
+	annotationKubernetesAppRoot                  = "ingress.kubernetes.io/app-root"
 
 	annotationKubernetesSSLRedirect             = "ingress.kubernetes.io/ssl-redirect"
 	annotationKubernetesHSTSMaxAge              = "ingress.kubernetes.io/hsts-max-age"

provider/kubernetes/kubernetes.go

@@ -226,7 +226,13 @@ func (p *Provider) loadIngresses(k8sClient Client) (*types.Configuration, error)
 					}
 				}
 
-				if rule := getRuleForPath(pa, i); rule != "" {
+				rule, err := getRuleForPath(pa, i)
+				if err != nil {
+					log.Errorf("Failed to get rule for ingress %s/%s: %s", i.Namespace, i.Name, err)
+					delete(templateObjects.Frontends, baseName)
+					continue
+				}
+				if rule != "" {
 					templateObjects.Frontends[baseName].Routes[pa.Path] = types.Route{
 						Rule: rule,
 					}
@@ -313,19 +319,34 @@ func (p *Provider) loadConfig(templateObjects types.Configuration) *types.Config
 	return configuration
 }
 
-func getRuleForPath(pa extensionsv1beta1.HTTPIngressPath, i *extensionsv1beta1.Ingress) string {
+func getRuleForPath(pa extensionsv1beta1.HTTPIngressPath, i *extensionsv1beta1.Ingress) (string, error) {
 	if len(pa.Path) == 0 {
-		return ""
+		return "", nil
 	}
 
 	ruleType := getStringValue(i.Annotations, annotationKubernetesRuleType, ruleTypePathPrefix)
 	rules := []string{ruleType + ":" + pa.Path}
 
+	var pathReplaceAnnotation string
+	if ruleType == ruleTypeReplacePath {
+		pathReplaceAnnotation = annotationKubernetesRuleType
+	}
+
 	if rewriteTarget := getStringValue(i.Annotations, annotationKubernetesRewriteTarget, ""); rewriteTarget != "" {
+		if pathReplaceAnnotation != "" {
+			return "", fmt.Errorf("rewrite-target must not be used together with annotation %q", pathReplaceAnnotation)
+		}
 		rules = append(rules, ruleTypeReplacePath+":"+rewriteTarget)
+		pathReplaceAnnotation = annotationKubernetesRewriteTarget
 	}
 
-	return strings.Join(rules, ";")
+	if rootPath := label.GetStringValue(i.Annotations, annotationKubernetesAppRoot, ""); rootPath != "" && pa.Path == "/" {
+		if pathReplaceAnnotation != "" {
+			return "", fmt.Errorf("app-root must not be used together with annotation %q", pathReplaceAnnotation)
+		}
+		rules = append(rules, ruleTypeReplacePath+":"+rootPath)
+	}
+	return strings.Join(rules, ";"), nil
 }
 
 func getRuleForHost(host string) string {

provider/kubernetes/kubernetes_test.go

@@ -737,6 +737,45 @@ rateset:
 					iPaths(onePath(iPath("/ratelimit"), iBackend("service1", intstr.FromInt(80))))),
 			),
 		),
+		buildIngress(
+			iNamespace("testing"),
+			iAnnotation(annotationKubernetesAppRoot, "/root"),
+			iRules(
+				iRule(
+					iHost("root"),
+					iPaths(
+						onePath(iPath("/"), iBackend("service1", intstr.FromInt(80))),
+						onePath(iPath("/root1"), iBackend("service1", intstr.FromInt(80))),
+					),
+				),
+			),
+		),
+		buildIngress(
+			iNamespace("testing"),
+			iAnnotation(annotationKubernetesAppRoot, "/root2"),
+			iAnnotation(annotationKubernetesRewriteTarget, "/abc"),
+			iRules(
+				iRule(
+					iHost("root2"),
+					iPaths(
+						onePath(iPath("/"), iBackend("service2", intstr.FromInt(80))),
+					),
+				),
+			),
+		),
+		buildIngress(
+			iNamespace("testing"),
+			iAnnotation(annotationKubernetesRuleType, ruleTypeReplacePath),
+			iAnnotation(annotationKubernetesRewriteTarget, "/abc"),
+			iRules(
+				iRule(
+					iHost("root2"),
+					iPaths(
+						onePath(iPath("/"), iBackend("service2", intstr.FromInt(80))),
+					),
+				),
+			),
+		),
 		buildIngress(
 			iNamespace("testing"),
 			iAnnotation(annotationKubernetesIngressClass, "traefik"),
@@ -880,6 +919,20 @@ rateset:
 					server("http://example.com", weight(1))),
 				lbMethod("wrr"),
 			),
+			backend("root/",
+				servers(
+					server("http://example.com", weight(1))),
+				lbMethod("wrr"),
+			),
+			backend("root/root1",
+				servers(
+					server("http://example.com", weight(1))),
+				lbMethod("wrr"),
+			),
+			backend("root2/",
+				servers(),
+				lbMethod("wrr"),
+			),
 		),
 		frontends(
 			frontend("foo/bar",
@@ -994,6 +1047,20 @@ rateset:
 					route("/customheaders", "PathPrefix:/customheaders"),
 					route("custom-headers", "Host:custom-headers")),
 			),
+			frontend("root/",
+				passHostHeader(),
+				routes(
+					route("/", "PathPrefix:/;ReplacePath:/root"),
+					route("root", "Host:root"),
+				),
+			),
+			frontend("root/root1",
+				passHostHeader(),
+				routes(
+					route("/root1", "PathPrefix:/root1"),
+					route("root", "Host:root"),
+				),
+			),
 		),
 	)