discovery(k8s): add a metric to track failed requests, failures will still be logged.

Signed-off-by: machine424 <ayoubmrini424@gmail.com>

discovery/kubernetes/kubernetes.go

@@ -485,8 +485,8 @@ func (d *Discovery) Run(ctx context.Context, ch chan<- []*targetgroup.Group) {
 			eps := NewEndpointSlice(
 				log.With(d.logger, "role", "endpointslice"),
 				informer,
-				cache.NewSharedInformer(slw, &apiv1.Service{}, resyncDisabled),
+				d.mustNewSharedInformer(slw, &apiv1.Service{}, resyncDisabled),
-				cache.NewSharedInformer(plw, &apiv1.Pod{}, resyncDisabled),
+				d.mustNewSharedInformer(plw, &apiv1.Pod{}, resyncDisabled),
 				nodeInf,
 				d.metrics.eventCount,
 			)
@@ -545,8 +545,8 @@ func (d *Discovery) Run(ctx context.Context, ch chan<- []*targetgroup.Group) {
 			eps := NewEndpoints(
 				log.With(d.logger, "role", "endpoint"),
 				d.newEndpointsByNodeInformer(elw),
-				cache.NewSharedInformer(slw, &apiv1.Service{}, resyncDisabled),
+				d.mustNewSharedInformer(slw, &apiv1.Service{}, resyncDisabled),
-				cache.NewSharedInformer(plw, &apiv1.Pod{}, resyncDisabled),
+				d.mustNewSharedInformer(plw, &apiv1.Pod{}, resyncDisabled),
 				nodeInf,
 				d.metrics.eventCount,
 			)
@@ -602,7 +602,7 @@ func (d *Discovery) Run(ctx context.Context, ch chan<- []*targetgroup.Group) {
 			}
 			svc := NewService(
 				log.With(d.logger, "role", "service"),
-				cache.NewSharedInformer(slw, &apiv1.Service{}, resyncDisabled),
+				d.mustNewSharedInformer(slw, &apiv1.Service{}, resyncDisabled),
 				d.metrics.eventCount,
 			)
 			d.discoverers = append(d.discoverers, svc)
@@ -641,7 +641,7 @@ func (d *Discovery) Run(ctx context.Context, ch chan<- []*targetgroup.Group) {
 						return i.Watch(ctx, options)
 					},
 				}
-				informer = cache.NewSharedInformer(ilw, &networkv1.Ingress{}, resyncDisabled)
+				informer = d.mustNewSharedInformer(ilw, &networkv1.Ingress{}, resyncDisabled)
 			} else {
 				i := d.client.NetworkingV1beta1().Ingresses(namespace)
 				ilw := &cache.ListWatch{
@@ -656,7 +656,7 @@ func (d *Discovery) Run(ctx context.Context, ch chan<- []*targetgroup.Group) {
 						return i.Watch(ctx, options)
 					},
 				}
-				informer = cache.NewSharedInformer(ilw, &v1beta1.Ingress{}, resyncDisabled)
+				informer = d.mustNewSharedInformer(ilw, &v1beta1.Ingress{}, resyncDisabled)
 			}
 			ingress := NewIngress(
 				log.With(d.logger, "role", "ingress"),
@@ -747,7 +747,7 @@ func (d *Discovery) newNodeInformer(ctx context.Context) cache.SharedInformer {
 			return d.client.CoreV1().Nodes().Watch(ctx, options)
 		},
 	}
-	return cache.NewSharedInformer(nlw, &apiv1.Node{}, resyncDisabled)
+	return d.mustNewSharedInformer(nlw, &apiv1.Node{}, resyncDisabled)
 }
 
 func (d *Discovery) newPodsByNodeInformer(plw *cache.ListWatch) cache.SharedIndexInformer {
@@ -762,7 +762,7 @@ func (d *Discovery) newPodsByNodeInformer(plw *cache.ListWatch) cache.SharedInde
 		}
 	}
 
-	return cache.NewSharedIndexInformer(plw, &apiv1.Pod{}, resyncDisabled, indexers)
+	return d.mustNewSharedIndexInformer(plw, &apiv1.Pod{}, resyncDisabled, indexers)
 }
 
 func (d *Discovery) newEndpointsByNodeInformer(plw *cache.ListWatch) cache.SharedIndexInformer {
@@ -783,7 +783,7 @@ func (d *Discovery) newEndpointsByNodeInformer(plw *cache.ListWatch) cache.Share
 		return pods, nil
 	}
 	if !d.attachMetadata.Node {
-		return cache.NewSharedIndexInformer(plw, &apiv1.Endpoints{}, resyncDisabled, indexers)
+		return d.mustNewSharedIndexInformer(plw, &apiv1.Endpoints{}, resyncDisabled, indexers)
 	}
 
 	indexers[nodeIndex] = func(obj interface{}) ([]string, error) {
@@ -809,13 +809,13 @@ func (d *Discovery) newEndpointsByNodeInformer(plw *cache.ListWatch) cache.Share
 		return nodes, nil
 	}
 
-	return cache.NewSharedIndexInformer(plw, &apiv1.Endpoints{}, resyncDisabled, indexers)
+	return d.mustNewSharedIndexInformer(plw, &apiv1.Endpoints{}, resyncDisabled, indexers)
 }
 
 func (d *Discovery) newEndpointSlicesByNodeInformer(plw *cache.ListWatch, object runtime.Object) cache.SharedIndexInformer {
 	indexers := make(map[string]cache.IndexFunc)
 	if !d.attachMetadata.Node {
-		return cache.NewSharedIndexInformer(plw, object, resyncDisabled, indexers)
+		return d.mustNewSharedIndexInformer(plw, object, resyncDisabled, indexers)
 	}
 
 	indexers[nodeIndex] = func(obj interface{}) ([]string, error) {
@@ -854,7 +854,32 @@ func (d *Discovery) newEndpointSlicesByNodeInformer(plw *cache.ListWatch, object
 		return nodes, nil
 	}
 
-	return cache.NewSharedIndexInformer(plw, object, resyncDisabled, indexers)
+	return d.mustNewSharedIndexInformer(plw, object, resyncDisabled, indexers)
+}
+
+func (d *Discovery) informerWatchErrorHandler(r *cache.Reflector, err error) {
+	d.metrics.failuresCount.Inc()
+	cache.DefaultWatchErrorHandler(r, err)
+}
+
+func (d *Discovery) mustNewSharedInformer(lw cache.ListerWatcher, exampleObject runtime.Object, defaultEventHandlerResyncPeriod time.Duration) cache.SharedInformer {
+	informer := cache.NewSharedInformer(lw, exampleObject, defaultEventHandlerResyncPeriod)
+	// Invoking SetWatchErrorHandler should fail only if the informer has been started beforehand.
+	// Such a scenario would suggest an incorrect use of the API, thus the panic.
+	if err := informer.SetWatchErrorHandler(d.informerWatchErrorHandler); err != nil {
+		panic(err)
+	}
+	return informer
+}
+
+func (d *Discovery) mustNewSharedIndexInformer(lw cache.ListerWatcher, exampleObject runtime.Object, defaultEventHandlerResyncPeriod time.Duration, indexers cache.Indexers) cache.SharedIndexInformer {
+	informer := cache.NewSharedIndexInformer(lw, exampleObject, defaultEventHandlerResyncPeriod, indexers)
+	// Invoking SetWatchErrorHandler should fail only if the informer has been started beforehand.
+	// Such a scenario would suggest an incorrect use of the API, thus the panic.
+	if err := informer.SetWatchErrorHandler(d.informerWatchErrorHandler); err != nil {
+		panic(err)
+	}
+	return informer
 }
 
 func checkDiscoveryV1Supported(client kubernetes.Interface) (bool, error) {

discovery/kubernetes/kubernetes_test.go

@@ -21,12 +21,16 @@ import (
 	"time"
 
 	"github.com/go-kit/log"
+	prom_testutil "github.com/prometheus/client_golang/prometheus/testutil"
 	"github.com/stretchr/testify/require"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/version"
+	"k8s.io/apimachinery/pkg/watch"
 	fakediscovery "k8s.io/client-go/discovery/fake"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/kubernetes/fake"
+	kubetesting "k8s.io/client-go/testing"
 	"k8s.io/client-go/tools/cache"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -314,3 +318,39 @@ func TestCheckNetworkingV1Supported(t *testing.T) {
 		})
 	}
 }
+
+func TestFailuresCountMetric(t *testing.T) {
+	tests := []struct {
+		role             Role
+		minFailedWatches int
+	}{
+		{RoleNode, 1},
+		{RolePod, 1},
+		{RoleService, 1},
+		{RoleEndpoint, 3},
+		{RoleEndpointSlice, 3},
+		{RoleIngress, 1},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(string(tc.role), func(t *testing.T) {
+			t.Parallel()
+
+			n, c := makeDiscovery(tc.role, NamespaceDiscovery{})
+			// The counter is initialized and no failures at the beginning.
+			require.Equal(t, float64(0), prom_testutil.ToFloat64(n.metrics.failuresCount))
+
+			// Simulate an error on watch requests.
+			c.Discovery().(*fakediscovery.FakeDiscovery).PrependWatchReactor("*", func(action kubetesting.Action) (bool, watch.Interface, error) {
+				return true, nil, apierrors.NewUnauthorized("unauthorized")
+			})
+
+			// Start the discovery.
+			k8sDiscoveryTest{discovery: n}.Run(t)
+
+			// At least the errors of the initial watches should be caught (watches are retried on errors).
+			require.GreaterOrEqual(t, prom_testutil.ToFloat64(n.metrics.failuresCount), float64(tc.minFailedWatches))
+		})
+	}
+}

discovery/kubernetes/metrics.go

@@ -23,6 +23,7 @@ var _ discovery.DiscovererMetrics = (*kubernetesMetrics)(nil)
 
 type kubernetesMetrics struct {
 	eventCount    *prometheus.CounterVec
+	failuresCount prometheus.Counter
 
 	metricRegisterer discovery.MetricRegisterer
 }
@@ -37,10 +38,18 @@ func newDiscovererMetrics(reg prometheus.Registerer, rmi discovery.RefreshMetric
 			},
 			[]string{"role", "event"},
 		),
+		failuresCount: prometheus.NewCounter(
+			prometheus.CounterOpts{
+				Namespace: discovery.KubernetesMetricsNamespace,
+				Name:      "failures_total",
+				Help:      "The number of failed WATCH/LIST requests.",
+			},
+		),
 	}
 
 	m.metricRegisterer = discovery.NewMetricRegisterer(reg, []prometheus.Collector{
 		m.eventCount,
+		m.failuresCount,
 	})
 
 	// Initialize metric vectors.
@@ -61,6 +70,8 @@ func newDiscovererMetrics(reg prometheus.Registerer, rmi discovery.RefreshMetric
 		}
 	}
 
+	m.failuresCount.Add(0)
+
 	return m
 }