From 32e08f351028caca182c4af450fb579767a67045 Mon Sep 17 00:00:00 2001
From: Luca Berneking <luca@berneking.net>
Date: Thu, 6 May 2021 18:12:10 +0200
Subject: [PATCH] Add k8s provider option to create services without endpoints

---
 docs/content/providers/kubernetes-ingress.md  | 24 +++++++++++
 .../reference/static-configuration/cli-ref.md |  3 ++
 .../reference/static-configuration/env-ref.md |  3 ++
 .../reference/static-configuration/file.toml  |  1 +
 .../reference/static-configuration/file.yaml  |  1 +
 integration/fixtures/k8s_default.toml         |  1 +
 ...h-one-service-without-endpoint_ingress.yml | 15 -------
 pkg/provider/kubernetes/ingress/kubernetes.go | 43 +++++++++++--------
 .../kubernetes/ingress/kubernetes_test.go     | 29 +++++++++----
 .../src/components/_commons/PanelServers.vue  | 27 +++++++++++-
 webui/src/pages/_commons/ServiceDetail.vue    |  2 +-
 11 files changed, 107 insertions(+), 42 deletions(-)
 delete mode 100644 pkg/provider/kubernetes/ingress/fixtures/Ingress-with-one-service-without-endpoint_ingress.yml

diff --git a/docs/content/providers/kubernetes-ingress.md b/docs/content/providers/kubernetes-ingress.md
index ccbde7969..a3b85e876 100644
--- a/docs/content/providers/kubernetes-ingress.md
+++ b/docs/content/providers/kubernetes-ingress.md
@@ -440,6 +440,30 @@ providers:
 --providers.kubernetesingress.throttleDuration=10s
 ```
 
+### `allowEmptyServices`
+
+_Optional, Default: false
+
+```toml tab="File (TOML)"
+[providers.kubernetesIngress]
+  allowEmptyServices = true
+  # ...
+```
+
+```yaml tab="File (YAML)"
+providers:
+  kubernetesIngress:
+    allowEmptyServices: true
+    # ...
+```
+
+```bash tab="CLI"
+--providers.kubernetesingress.allowEmptyServices=true
+```
+
+Allow the creation of services if there are no endpoints available.
+This results in `503` http responses instead of `404`.
+
 ### Further
 
 To learn more about the various aspects of the Ingress specification that Traefik supports,
diff --git a/docs/content/reference/static-configuration/cli-ref.md b/docs/content/reference/static-configuration/cli-ref.md
index 55ed8220c..4d8628cc7 100644
--- a/docs/content/reference/static-configuration/cli-ref.md
+++ b/docs/content/reference/static-configuration/cli-ref.md
@@ -624,6 +624,9 @@ Kubernetes bearer token (not needed for in-cluster client).
 `--providers.kubernetesingress`:  
 Enable Kubernetes backend with default settings. (Default: ```false```)
 
+`--providers.kubernetesingress.allowemptyservices`:  
+Allow creation of services without endpoints. (Default: ```false```)
+
 `--providers.kubernetesingress.certauthfilepath`:  
 Kubernetes certificate authority file path (not needed for in-cluster client).
 
diff --git a/docs/content/reference/static-configuration/env-ref.md b/docs/content/reference/static-configuration/env-ref.md
index dc291158c..85cbe0106 100644
--- a/docs/content/reference/static-configuration/env-ref.md
+++ b/docs/content/reference/static-configuration/env-ref.md
@@ -624,6 +624,9 @@ Kubernetes bearer token (not needed for in-cluster client).
 `TRAEFIK_PROVIDERS_KUBERNETESINGRESS`:  
 Enable Kubernetes backend with default settings. (Default: ```false```)
 
+`TRAEFIK_PROVIDERS_KUBERNETESINGRESS_ALLOWEMPTYSERVICES`:  
+Allow creation of services without endpoints. (Default: ```false```)
+
 `TRAEFIK_PROVIDERS_KUBERNETESINGRESS_CERTAUTHFILEPATH`:  
 Kubernetes certificate authority file path (not needed for in-cluster client).
 
diff --git a/docs/content/reference/static-configuration/file.toml b/docs/content/reference/static-configuration/file.toml
index 84c5c97f5..361b8ef3f 100644
--- a/docs/content/reference/static-configuration/file.toml
+++ b/docs/content/reference/static-configuration/file.toml
@@ -106,6 +106,7 @@
     labelSelector = "foobar"
     ingressClass = "foobar"
     throttleDuration = "42s"
+    allowEmptyServices = true
     [providers.kubernetesIngress.ingressEndpoint]
       ip = "foobar"
       hostname = "foobar"
diff --git a/docs/content/reference/static-configuration/file.yaml b/docs/content/reference/static-configuration/file.yaml
index 6a550e236..fa49b9db3 100644
--- a/docs/content/reference/static-configuration/file.yaml
+++ b/docs/content/reference/static-configuration/file.yaml
@@ -114,6 +114,7 @@ providers:
     labelSelector: foobar
     ingressClass: foobar
     throttleDuration: 42s
+    allowEmptyServices: true
     ingressEndpoint:
       ip: foobar
       hostname: foobar
diff --git a/integration/fixtures/k8s_default.toml b/integration/fixtures/k8s_default.toml
index 3c0d9e790..f94ecf45b 100644
--- a/integration/fixtures/k8s_default.toml
+++ b/integration/fixtures/k8s_default.toml
@@ -13,3 +13,4 @@
     address = ":8000"
 
 [providers.kubernetesIngress]
+  allowEmptyServices = true
diff --git a/pkg/provider/kubernetes/ingress/fixtures/Ingress-with-one-service-without-endpoint_ingress.yml b/pkg/provider/kubernetes/ingress/fixtures/Ingress-with-one-service-without-endpoint_ingress.yml
deleted file mode 100644
index 4e27d7f07..000000000
--- a/pkg/provider/kubernetes/ingress/fixtures/Ingress-with-one-service-without-endpoint_ingress.yml
+++ /dev/null
@@ -1,15 +0,0 @@
-kind: Ingress
-apiVersion: networking.k8s.io/v1beta1
-metadata:
-  name: ""
-  namespace: testing
-
-spec:
-  rules:
-  - host: traefik.tchouk
-    http:
-      paths:
-      - path: /bar
-        backend:
-          serviceName: service1
-          servicePort: 80
diff --git a/pkg/provider/kubernetes/ingress/kubernetes.go b/pkg/provider/kubernetes/ingress/kubernetes.go
index 31fe71aa0..778067c0e 100644
--- a/pkg/provider/kubernetes/ingress/kubernetes.go
+++ b/pkg/provider/kubernetes/ingress/kubernetes.go
@@ -37,15 +37,16 @@ const (
 
 // Provider holds configurations of the provider.
 type Provider struct {
-	Endpoint          string           `description:"Kubernetes server endpoint (required for external cluster client)." json:"endpoint,omitempty" toml:"endpoint,omitempty" yaml:"endpoint,omitempty"`
-	Token             string           `description:"Kubernetes bearer token (not needed for in-cluster client)." json:"token,omitempty" toml:"token,omitempty" yaml:"token,omitempty"`
-	CertAuthFilePath  string           `description:"Kubernetes certificate authority file path (not needed for in-cluster client)." json:"certAuthFilePath,omitempty" toml:"certAuthFilePath,omitempty" yaml:"certAuthFilePath,omitempty"`
-	Namespaces        []string         `description:"Kubernetes namespaces." json:"namespaces,omitempty" toml:"namespaces,omitempty" yaml:"namespaces,omitempty" export:"true"`
-	LabelSelector     string           `description:"Kubernetes Ingress label selector to use." json:"labelSelector,omitempty" toml:"labelSelector,omitempty" yaml:"labelSelector,omitempty" export:"true"`
-	IngressClass      string           `description:"Value of kubernetes.io/ingress.class annotation or IngressClass name to watch for." json:"ingressClass,omitempty" toml:"ingressClass,omitempty" yaml:"ingressClass,omitempty" export:"true"`
-	IngressEndpoint   *EndpointIngress `description:"Kubernetes Ingress Endpoint." json:"ingressEndpoint,omitempty" toml:"ingressEndpoint,omitempty" yaml:"ingressEndpoint,omitempty" export:"true"`
-	ThrottleDuration  ptypes.Duration  `description:"Ingress refresh throttle duration" json:"throttleDuration,omitempty" toml:"throttleDuration,omitempty" yaml:"throttleDuration,omitempty" export:"true"`
-	lastConfiguration safe.Safe
+	Endpoint           string           `description:"Kubernetes server endpoint (required for external cluster client)." json:"endpoint,omitempty" toml:"endpoint,omitempty" yaml:"endpoint,omitempty"`
+	Token              string           `description:"Kubernetes bearer token (not needed for in-cluster client)." json:"token,omitempty" toml:"token,omitempty" yaml:"token,omitempty"`
+	CertAuthFilePath   string           `description:"Kubernetes certificate authority file path (not needed for in-cluster client)." json:"certAuthFilePath,omitempty" toml:"certAuthFilePath,omitempty" yaml:"certAuthFilePath,omitempty"`
+	Namespaces         []string         `description:"Kubernetes namespaces." json:"namespaces,omitempty" toml:"namespaces,omitempty" yaml:"namespaces,omitempty" export:"true"`
+	LabelSelector      string           `description:"Kubernetes Ingress label selector to use." json:"labelSelector,omitempty" toml:"labelSelector,omitempty" yaml:"labelSelector,omitempty" export:"true"`
+	IngressClass       string           `description:"Value of kubernetes.io/ingress.class annotation or IngressClass name to watch for." json:"ingressClass,omitempty" toml:"ingressClass,omitempty" yaml:"ingressClass,omitempty" export:"true"`
+	IngressEndpoint    *EndpointIngress `description:"Kubernetes Ingress Endpoint." json:"ingressEndpoint,omitempty" toml:"ingressEndpoint,omitempty" yaml:"ingressEndpoint,omitempty" export:"true"`
+	ThrottleDuration   ptypes.Duration  `description:"Ingress refresh throttle duration" json:"throttleDuration,omitempty" toml:"throttleDuration,omitempty" yaml:"throttleDuration,omitempty" export:"true"`
+	AllowEmptyServices bool             `description:"Allow creation of services without endpoints." json:"allowEmptyServices,omitempty" toml:"allowEmptyServices,omitempty" yaml:"allowEmptyServices,omitempty" export:"true"`
+	lastConfiguration  safe.Safe
 }
 
 // EndpointIngress holds the endpoint information for the Kubernetes provider.
@@ -241,6 +242,14 @@ func (p *Provider) loadConfigurationFromIngresses(ctx context.Context, client Cl
 				continue
 			}
 
+			if len(service.LoadBalancer.Servers) == 0 && !p.AllowEmptyServices {
+				log.FromContext(ctx).
+					WithField("serviceName", ingress.Spec.DefaultBackend.Service.Name).
+					WithField("servicePort", ingress.Spec.DefaultBackend.Service.Port.String()).
+					Errorf("Skipping service: no endpoints found")
+				continue
+			}
+
 			rt := &dynamic.Router{
 				Rule:     "PathPrefix(`/`)",
 				Priority: math.MinInt32,
@@ -278,6 +287,14 @@ func (p *Provider) loadConfigurationFromIngresses(ctx context.Context, client Cl
 					continue
 				}
 
+				if len(service.LoadBalancer.Servers) == 0 && !p.AllowEmptyServices {
+					log.FromContext(ctx).
+						WithField("serviceName", pa.Backend.Service.Name).
+						WithField("servicePort", pa.Backend.Service.Port.String()).
+						Errorf("Skipping service: no endpoints found")
+					continue
+				}
+
 				portString := pa.Backend.Service.Port.Name
 
 				if len(pa.Backend.Service.Port.Name) == 0 {
@@ -534,10 +551,6 @@ func loadService(client Client, namespace string, backend networkingv1.IngressBa
 		return nil, errors.New("endpoints not found")
 	}
 
-	if len(endpoints.Subsets) == 0 {
-		return nil, errors.New("subset not found")
-	}
-
 	var port int32
 	for _, subset := range endpoints.Subsets {
 		for _, p := range subset.Ports {
@@ -562,10 +575,6 @@ func loadService(client Client, namespace string, backend networkingv1.IngressBa
 		}
 	}
 
-	if len(svc.LoadBalancer.Servers) == 0 {
-		return nil, errors.New("no valid subset found")
-	}
-
 	return svc, nil
 }
 
diff --git a/pkg/provider/kubernetes/ingress/kubernetes_test.go b/pkg/provider/kubernetes/ingress/kubernetes_test.go
index 66d05c9f5..663cec314 100644
--- a/pkg/provider/kubernetes/ingress/kubernetes_test.go
+++ b/pkg/provider/kubernetes/ingress/kubernetes_test.go
@@ -24,10 +24,11 @@ func Bool(v bool) *bool { return &v }
 
 func TestLoadConfigurationFromIngresses(t *testing.T) {
 	testCases := []struct {
-		desc          string
-		ingressClass  string
-		serverVersion string
-		expected      *dynamic.Configuration
+		desc               string
+		ingressClass       string
+		serverVersion      string
+		expected           *dynamic.Configuration
+		allowEmptyServices bool
 	}{
 		{
 			desc: "Empty ingresses",
@@ -444,13 +445,25 @@ func TestLoadConfigurationFromIngresses(t *testing.T) {
 			},
 		},
 		{
-			desc: "Ingress with one service without endpoints subset",
+			desc:               "Ingress with one service without endpoints subset",
+			allowEmptyServices: true,
 			expected: &dynamic.Configuration{
 				TCP: &dynamic.TCPConfiguration{},
 				HTTP: &dynamic.HTTPConfiguration{
 					Middlewares: map[string]*dynamic.Middleware{},
-					Routers:     map[string]*dynamic.Router{},
-					Services:    map[string]*dynamic.Service{},
+					Routers: map[string]*dynamic.Router{
+						"testing-traefik-tchouk-bar": {
+							Rule:    "Host(`traefik.tchouk`) && PathPrefix(`/bar`)",
+							Service: "testing-service1-80",
+						},
+					},
+					Services: map[string]*dynamic.Service{
+						"testing-service1-80": {
+							LoadBalancer: &dynamic.ServersLoadBalancer{
+								PassHostHeader: Bool(true),
+							},
+						},
+					},
 				},
 			},
 		},
@@ -1631,7 +1644,7 @@ func TestLoadConfigurationFromIngresses(t *testing.T) {
 
 			clientMock := newClientMock(serverVersion, paths...)
 
-			p := Provider{IngressClass: test.ingressClass}
+			p := Provider{IngressClass: test.ingressClass, AllowEmptyServices: test.allowEmptyServices}
 			conf := p.loadConfigurationFromIngresses(context.Background(), clientMock)
 
 			assert.Equal(t, test.expected, conf)
diff --git a/webui/src/components/_commons/PanelServers.vue b/webui/src/components/_commons/PanelServers.vue
index dcd89b725..78f148f89 100644
--- a/webui/src/components/_commons/PanelServers.vue
+++ b/webui/src/components/_commons/PanelServers.vue
@@ -1,6 +1,6 @@
 <template>
   <q-card flat bordered v-bind:class="['panel-servers', {'panel-servers-dense':isDense}]">
-    <q-scroll-area :thumb-style="appThumbStyle" style="height:100%;">
+    <q-scroll-area v-if="data.loadBalancer.servers" :thumb-style="appThumbStyle" style="height:100%;">
       <q-card-section>
         <div class="row items-start no-wrap">
           <div class="col-3" v-if="showStatus">
@@ -33,6 +33,18 @@
         <q-separator />
       </div>
     </q-scroll-area>
+      <q-card-section v-else style="height: 100%">
+        <div class="row items-center" style="height: 100%">
+          <div class="col-12">
+            <div class="block-empty"></div>
+            <div class="q-pb-lg block-empty-logo">
+              <img v-if="$q.dark.isActive" alt="empty" src="~assets/middlewares-empty-dark.svg">
+              <img v-else alt="empty" src="~assets/middlewares-empty.svg">
+            </div>
+            <div class="block-empty-label">There is no<br>Server available</div>
+          </div>
+        </div>
+      </q-card-section>
   </q-card>
 </template>
 
@@ -121,6 +133,19 @@ export default {
       letter-spacing: normal;
       text-transform: none;
     }
+
+    .block-empty {
+      &-logo {
+         text-align: center;
+       }
+      &-label {
+         font-size: 20px;
+         font-weight: 700;
+         color: #b8b8b8;
+         text-align: center;
+         line-height: 1.2;
+       }
+    }
   }
 
 </style>
diff --git a/webui/src/pages/_commons/ServiceDetail.vue b/webui/src/pages/_commons/ServiceDetail.vue
index 68c158bbc..0fc9b40ef 100644
--- a/webui/src/pages/_commons/ServiceDetail.vue
+++ b/webui/src/pages/_commons/ServiceDetail.vue
@@ -45,7 +45,7 @@
             </div>
           </div>
 
-          <div v-if="serviceByName.item.loadBalancer && serviceByName.item.loadBalancer.servers" class="col-12 col-md-4 q-mb-lg path-block">
+          <div v-if="serviceByName.item.loadBalancer" class="col-12 col-md-4 q-mb-lg path-block">
             <div class="row no-wrap items-center q-mb-lg app-title">
               <q-icon name="eva-globe-outline"></q-icon>
               <div class="app-title-label">Servers</div>