Allow any kubernetes ingressClass value

docs/configuration/backends/kubernetes.md

@@ -54,8 +54,6 @@ See also [Kubernetes user guide](/user-guide/kubernetes).
 # If the parameter is non-empty, only Ingresses containing an annotation with the same value are processed.
 # Otherwise, Ingresses missing the annotation, having an empty value, or the value `traefik` are processed.
 #
-# Note : `ingressClass` option must begin with the "traefik" prefix.
-#
 # Optional
 # Default: empty
 #

docs/user-guide/kubernetes.md

@@ -859,12 +859,14 @@ Sometimes Træfik runs along other Ingress controller implementations. One such
 The `kubernetes.io/ingress.class` annotation can be attached to any Ingress object in order to control whether Træfik should handle it.
 
 If the annotation is missing, contains an empty value, or the value `traefik`, then the Træfik controller will take responsibility and process the associated Ingress object.
-If the annotation contains any other value (usually the name of a different Ingress controller), Træfik will ignore the object.
 
-It is also possible to set the `ingressClass` option in Træfik to a particular value.
-If that's the case and the value contains a `traefik` prefix, then only those Ingress objects matching the same value will be processed.
+It is also possible to set the `ingressClass` option in Træfik to a particular value. Træfik will only process matching Ingress objects.
 For instance, setting the option to `traefik-internal` causes Træfik to process Ingress objects with the same `kubernetes.io/ingress.class` annotation value, ignoring all other objects (including those with a `traefik` value, empty value, and missing annotation).
 
+!!! note
+    Letting multiple ingress controllers handle the same ingress objects can lead to unintended behavior.
+    It is recommended to prefix all ingressClass values with `traefik` to avoid unintended collisions with other ingress implementations.
+
 ### Between multiple Træfik Deployments
 
 Sometimes multiple Træfik Deployments are supposed to run concurrently.

provider/kubernetes/kubernetes.go

@@ -100,12 +100,6 @@ func (p *Provider) Provide(configurationChan chan<- types.ConfigMessage, pool *s
 		return err
 	}
 
-	// We require that IngressClasses start with `traefik` to reduce chances of
-	// conflict with other Ingress Providers
-	if len(p.IngressClass) > 0 && !strings.HasPrefix(p.IngressClass, traefikDefaultIngressClass) {
-		return fmt.Errorf("value for IngressClass has to be empty or start with the prefix %q, instead found %q", traefikDefaultIngressClass, p.IngressClass)
-	}
-
 	log.Debugf("Using Ingress label selector: %q", p.LabelSelector)
 	k8sClient, err := p.newK8sClient(p.LabelSelector)
 	if err != nil {

provider/kubernetes/kubernetes_test.go

@@ -1165,8 +1165,17 @@ func TestIngressClassAnnotation(t *testing.T) {
 			iAnnotation(annotationKubernetesIngressClass, traefikDefaultIngressClass+"-other"),
 			iRules(
 				iRule(
-					iHost("herp"),
-					iPaths(onePath(iPath("/derp"), iBackend("service1", intstr.FromInt(80))))),
+					iHost("foo"),
+					iPaths(onePath(iPath("/bar"), iBackend("service1", intstr.FromInt(80))))),
+			),
+		),
+		buildIngress(
+			iNamespace("testing"),
+			iAnnotation(annotationKubernetesIngressClass, "custom"),
+			iRules(
+				iRule(
+					iHost("foo"),
+					iPaths(onePath(iPath("/bar"), iBackend("service2", intstr.FromInt(80))))),
 			),
 		),
 	}
@@ -1182,12 +1191,32 @@ func TestIngressClassAnnotation(t *testing.T) {
 				sExternalName("example.com"),
 				sPorts(sPort(80, "http"))),
 		),
+		buildService(
+			sName("service2"),
+			sNamespace("testing"),
+			sUID("2"),
+			sSpec(
+				clusterIP("10.0.0.2"),
+				sPorts(sPort(80, "http"))),
+		),
+	}
+
+	endpoints := []*corev1.Endpoints{
+		buildEndpoint(
+			eName("service2"),
+			eUID("1"),
+			eNamespace("testing"),
+			subset(
+				eAddresses(eAddress("10.10.0.1")),
+				ePorts(ePort(80, "http"))),
+		),
 	}
 
 	watchChan := make(chan interface{})
 	client := clientMock{
 		ingresses: ingresses,
 		services:  services,
+		endpoints: endpoints,
 		watchChan: watchChan,
 	}
 
@@ -1247,19 +1276,39 @@ func TestIngressClassAnnotation(t *testing.T) {
 			provider: Provider{IngressClass: traefikDefaultRealm + "-other"},
 			expected: buildConfiguration(
 				backends(
-					backend("herp/derp",
+					backend("foo/bar",
 						servers(
-							server("http://example.com", weight(1)),
 							server("http://example.com", weight(1))),
 						lbMethod("wrr"),
 					),
 				),
 				frontends(
-					frontend("herp/derp",
+					frontend("foo/bar",
 						passHostHeader(),
 						routes(
-							route("/derp", "PathPrefix:/derp"),
-							route("herp", "Host:herp")),
+							route("/bar", "PathPrefix:/bar"),
+							route("foo", "Host:foo")),
+					),
+				),
+			),
+		},
+		{
+			desc:     "Provided IngressClass annotation",
+			provider: Provider{IngressClass: "custom"},
+			expected: buildConfiguration(
+				backends(
+					backend("foo/bar",
+						servers(
+							server("http://10.10.0.1:80", weight(1))),
+						lbMethod("wrr"),
+					),
+				),
+				frontends(
+					frontend("foo/bar",
+						passHostHeader(),
+						routes(
+							route("/bar", "PathPrefix:/bar"),
+							route("foo", "Host:foo")),
 					),
 				),
 			),