internal/k8s: add check to verify resources exist in cluster

Add a discovery client to look up server groups and resources which
allows for a check to be made that a resource type exists before
starting any informers against.

Fixes projectcontour#2219

Signed-off-by: Steve Sloka <[email protected]>

cmd/contour/serve.go

@@ -241,8 +241,14 @@ func doServe(log logrus.FieldLogger, ctx *serveContext) error {
 	informerSyncList.InformOnResources(clusterInformerFactory, dynamicHandler, k8s.DefaultResources()...)
 
 	if ctx.UseExperimentalServiceAPITypes {
-		informerSyncList.InformOnResources(clusterInformerFactory,
-			dynamicHandler, k8s.ServiceAPIResources()...)
+		for _, s := range k8s.ServiceAPIResources() {
+			// Check if the resource exists in the API server before setting up the informer.
+			if !clients.ResourceExists(s) {
+				log.WithField("InformOnResources", "ExperimentalServiceAPITypes").Warnf("resource %v not found in api server", s.String())
+				continue
+			}
+			informerSyncList.InformOnResources(clusterInformerFactory, dynamicHandler, s)
+		}
 	}
 
 	// TODO(youngnick): Move this logic out to internal/k8s/informers.go somehow.
@@ -369,6 +375,7 @@ func doServe(log logrus.FieldLogger, ctx *serveContext) error {
 		}
 		factory := clients.NewInformerFactoryForNamespace(ctx.EnvoyServiceNamespace)
 		informerSyncList.InformOnResources(factory, dynamicServiceHandler, k8s.ServicesResources()...)
+
 		g.Add(startInformer(factory, log.WithField("context", "serviceStatusLoadBalancerWatcher")))
 		log.WithField("envoy-service-name", ctx.EnvoyServiceName).
 			WithField("envoy-service-namespace", ctx.EnvoyServiceNamespace).

internal/k8s/clients.go

@@ -16,6 +16,10 @@ package k8s
 import (
 	"time"
 
+	"k8s.io/apimachinery/pkg/runtime/schema"
+
+	"k8s.io/client-go/discovery"
+
 	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/dynamic/dynamicinformer"
 	"k8s.io/client-go/kubernetes"
@@ -25,8 +29,11 @@ import (
 
 // Clients holds the various API clients required by Contour.
 type Clients struct {
-	core    *kubernetes.Clientset
-	dynamic dynamic.Interface
+	core      *kubernetes.Clientset
+	dynamic   dynamic.Interface
+	discovery *discovery.DiscoveryClient
+
+	apiResources *APIResources
 }
 
 // NewClients returns a new set of the various API clients required
@@ -35,6 +42,7 @@ type Clients struct {
 func NewClients(kubeconfig string, inCluster bool) (*Clients, error) {
 	config, err := newRestConfig(kubeconfig, inCluster)
 	if err != nil {
+
 		return nil, err
 	}
 
@@ -49,6 +57,17 @@ func NewClients(kubeconfig string, inCluster bool) (*Clients, error) {
 		return nil, err
 	}
 
+	clients.discovery, err = discovery.NewDiscoveryClientForConfig(config)
+	if err != nil {
+		return nil, err
+	}
+
+	// populate the apiResources cache
+	clients.apiResources, err = clients.serverResources()
+	if err != nil {
+		return nil, err
+	}
+
 	return &clients, nil
 }
 
@@ -84,3 +103,31 @@ func (c *Clients) ClientSet() *kubernetes.Clientset {
 func (c *Clients) DynamicClient() dynamic.Interface {
 	return c.dynamic
 }
+
+// APIResources holds a map of API, GroupVersionResources, that exist in the Kubernetes cluster
+type APIResources struct {
+	serverResources map[schema.GroupVersionResource]struct{}
+}
+
+// serverResources returns the list of all the resources supported
+// by the API server. Note that this method guarantees to populate the
+// Group and Version fields in the result.
+func (c *Clients) serverResources() (*APIResources, error) {
+	_, apiList, err := c.discovery.ServerGroupsAndResources()
+	if err != nil {
+		return nil, err
+	}
+
+	gvrs, err := discovery.GroupVersionResources(apiList)
+	return &APIResources{
+		serverResources: gvrs,
+	}, err
+}
+
+// ResourceExists returns true if an GroupVersionResource exists in the cluster.
+func (c *Clients) ResourceExists(gvr schema.GroupVersionResource) bool {
+	if _, ok := c.apiResources.serverResources[gvr]; ok {
+		return true
+	}
+	return false
+}

internal/k8s/clients_test.go

@@ -0,0 +1,75 @@
+// Copyright Project Contour 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 k8s
+
+import (
+	"testing"
+
+	"k8s.io/apimachinery/pkg/runtime/schema"
+
+	"github.com/projectcontour/contour/internal/assert"
+)
+
+func TestResourceKindExists(t *testing.T) {
+	type testcase struct {
+		gvr             schema.GroupVersionResource
+		apiResourceList map[schema.GroupVersionResource]struct{}
+		want            bool
+	}
+
+	run := func(t *testing.T, name string, tc testcase) {
+		t.Helper()
+
+		t.Run(name, func(t *testing.T) {
+			t.Helper()
+
+			clients := &Clients{
+				apiResources: &APIResources{
+					serverResources: tc.apiResourceList,
+				},
+			}
+			got := clients.ResourceExists(tc.gvr)
+			assert.Equal(t, tc.want, got)
+		})
+	}
+
+	valid := schema.GroupVersionResource{
+		Group:    "networking.k8s.io",
+		Version:  "v1beta1",
+		Resource: "ingress",
+	}
+
+	invalid := schema.GroupVersionResource{
+		Group:    "networking.k8s.io",
+		Version:  "v1beta1",
+		Resource: "ingressclass",
+	}
+
+	run(t, "ingress exist", testcase{
+		gvr:  valid,
+		want: true,
+		apiResourceList: map[schema.GroupVersionResource]struct{}{
+			valid: struct{}{},
+		},
+	})
+
+	run(t, "ingressclass does not exist", testcase{
+		gvr:  invalid,
+		want: false,
+		apiResourceList: map[schema.GroupVersionResource]struct{}{
+			valid: struct{}{},
+		},
+	})
+
+}