Allow setting circuitbreaker expression via Kubernetes annotation (#1056)

docs/toml.md

@@ -1068,6 +1068,10 @@ Annotations can be used on the Kubernetes service to override default behaviour:
 
 You can find here an example [ingress](https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/cheese-ingress.yaml) and [replication controller](https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/traefik.yaml).
 
+Additionally, an annotation can be used on Kubernetes services to set the [circuit breaker expression](https://docs.traefik.io/basics/#backends) for a backend.
+
+- `traefik.backend.circuitbreaker: <expression>`: set the circuit breaker expression for the backend (Default: nil).
+
 ## Consul backend
 
 Træfɪk can be configured to use Consul as a backend configuration:

docs/user-guide/kubernetes.md

@@ -299,6 +299,8 @@ apiVersion: v1
 kind: Service
 metadata:
   name: wensleydale
+  annotations:
+    traefik.backend.circuitbreaker: "NetworkErrorRatio() > 0.5"
 spec:
   ports:
   - name: http
@@ -308,6 +310,11 @@ spec:
     app: cheese
     task: wensleydale
 ```
+
+> Notice that we also set a [circuit breaker expression](https://docs.traefik.io/basics/#backends) for one of the backends
+> by setting the `traefik.backend.circuitbreaker` annotation on the service.
+
+
 [examples/k8s/cheese-services.yaml](https://github.com/containous/traefik/tree/master/examples/k8s/cheese-services.yaml)
 
 ```sh

provider/kubernetes.go

@@ -175,12 +175,18 @@ func (provider *Kubernetes) loadIngresses(k8sClient k8s.Client) (*types.Configur
 					continue
 				}
 
+				if expression := service.Annotations["traefik.backend.circuitbreaker"]; expression != "" {
+					templateObjects.Backends[r.Host+pa.Path].CircuitBreaker = &types.CircuitBreaker{
+						Expression: expression,
+					}
+				}
 				if service.Annotations["traefik.backend.loadbalancer.method"] == "drr" {
 					templateObjects.Backends[r.Host+pa.Path].LoadBalancer.Method = "drr"
 				}
 				if service.Annotations["traefik.backend.loadbalancer.sticky"] == "true" {
 					templateObjects.Backends[r.Host+pa.Path].LoadBalancer.Sticky = true
 				}
+
 				protocol := "http"
 				for _, port := range service.Spec.Ports {
 					if equalPorts(port, pa.Backend.ServicePort) {

provider/kubernetes_test.go

@@ -1288,7 +1288,7 @@ func TestHostlessIngress(t *testing.T) {
 	}
 }
 
-func TestLoadBalancerAnnotation(t *testing.T) {
+func TestServiceAnnotations(t *testing.T) {
 	ingresses := []*v1beta1.Ingress{{
 		ObjectMeta: v1.ObjectMeta{
 			Namespace: "testing",
@@ -1336,6 +1336,7 @@ func TestLoadBalancerAnnotation(t *testing.T) {
 				UID:       "1",
 				Namespace: "testing",
 				Annotations: map[string]string{
+					"traefik.backend.circuitbreaker":      "NetworkErrorRatio() > 0.5",
 					"traefik.backend.loadbalancer.method": "drr",
 				},
 			},
@@ -1354,6 +1355,7 @@ func TestLoadBalancerAnnotation(t *testing.T) {
 				UID:       "2",
 				Namespace: "testing",
 				Annotations: map[string]string{
+					"traefik.backend.circuitbreaker":      "",
 					"traefik.backend.loadbalancer.sticky": "true",
 				},
 			},
@@ -1463,7 +1465,9 @@ func TestLoadBalancerAnnotation(t *testing.T) {
 						Weight: 1,
 					},
 				},
-				CircuitBreaker: nil,
+				CircuitBreaker: &types.CircuitBreaker{
+					Expression: "NetworkErrorRatio() > 0.5",
+				},
 				LoadBalancer: &types.LoadBalancer{
 					Method: "drr",
 					Sticky: false,

templates/kubernetes.tmpl

@@ -1,4 +1,8 @@
 [backends]{{range $backendName, $backend := .Backends}}
+    {{if $backend.CircuitBreaker}}
+    [backends."{{$backendName}}".circuitbreaker]
+      expression = "{{$backend.CircuitBreaker.Expression}}"
+    {{end}}
     [backends."{{$backendName}}".loadbalancer]
       method = "{{$backend.LoadBalancer.Method}}"
       {{if $backend.LoadBalancer.Sticky}}