Merge pull request kubernetes#125675 from tnqn/fix-rapid-endpoints-update

Fix endpoints status out-of-sync when the pod state changes rapidly

Author: k8s-ci-robot

pkg/controller/endpoint/endpoints_controller.go

@@ -110,6 +110,7 @@ func NewEndpointController(ctx context.Context, podInformer coreinformers.PodInf
 	e.endpointsLister = endpointsInformer.Lister()
 	e.endpointsSynced = endpointsInformer.Informer().HasSynced
 
+	e.staleEndpointsTracker = newStaleEndpointsTracker()
 	e.triggerTimeTracker = endpointsliceutil.NewTriggerTimeTracker()
 	e.eventBroadcaster = broadcaster
 	e.eventRecorder = recorder
@@ -145,6 +146,8 @@ type Controller struct {
 	// endpointsSynced returns true if the endpoints shared informer has been synced at least once.
 	// Added as a member to the struct to allow injection for testing.
 	endpointsSynced cache.InformerSynced
+	// staleEndpointsTracker can help determine if a cached Endpoints is out of date.
+	staleEndpointsTracker *staleEndpointsTracker
 
 	// Services that need to be updated. A channel is inappropriate here,
 	// because it allows services with lots of pods to be serviced much
@@ -384,6 +387,7 @@ func (e *Controller) syncService(ctx context.Context, key string) error {
 			return err
 		}
 		e.triggerTimeTracker.DeleteService(namespace, name)
+		e.staleEndpointsTracker.Delete(namespace, name)
 		return nil
 	}
 
@@ -473,6 +477,8 @@ func (e *Controller) syncService(ctx context.Context, key string) error {
 				Labels: service.Labels,
 			},
 		}
+	} else if e.staleEndpointsTracker.IsStale(currentEndpoints) {
+		return fmt.Errorf("endpoints informer cache is out of date, resource version %s already processed for endpoints %s", currentEndpoints.ResourceVersion, key)
 	}
 
 	createEndpoints := len(currentEndpoints.ResourceVersion) == 0
@@ -555,6 +561,12 @@ func (e *Controller) syncService(ctx context.Context, key string) error {
 
 		return err
 	}
+	// If the current endpoints is updated we track the old resource version, so
+	// if we obtain this resource version again from the lister we know is outdated
+	// and we need to retry later to wait for the informer cache to be up-to-date.
+	if !createEndpoints {
+		e.staleEndpointsTracker.Stale(currentEndpoints)
+	}
 	return nil
 }
 

pkg/controller/endpoint/endpoints_controller_test.go

@@ -160,10 +160,10 @@ func makeTestServer(t *testing.T, namespace string) (*httptest.Server, *utiltest
 	return httptest.NewServer(mux), &fakeEndpointsHandler
 }
 
-// makeBlockingEndpointDeleteTestServer will signal the blockNextAction channel on endpoint "POST" & "DELETE" requests. All
-// block endpoint "DELETE" requestsi will wait on a blockDelete signal to delete endpoint. If controller is nil, a error will
-// be sent in the response.
-func makeBlockingEndpointDeleteTestServer(t *testing.T, controller *endpointController, endpoint *v1.Endpoints, blockDelete, blockNextAction chan struct{}, namespace string) *httptest.Server {
+// makeBlockingEndpointTestServer will signal the blockNextAction channel on endpoint "POST", "PUT", and "DELETE"
+// requests. "POST" and "PUT" requests will wait on a blockUpdate signal if provided, while "DELETE" requests will wait
+// on a blockDelete signal if provided. If controller is nil, an error will be sent in the response.
+func makeBlockingEndpointTestServer(t *testing.T, controller *endpointController, endpoint *v1.Endpoints, blockUpdate, blockDelete, blockNextAction chan struct{}, namespace string) *httptest.Server {
 
 	handlerFunc := func(res http.ResponseWriter, req *http.Request) {
 		if controller == nil {
@@ -172,23 +172,37 @@ func makeBlockingEndpointDeleteTestServer(t *testing.T, controller *endpointCont
 			return
 		}
 
-		if req.Method == "POST" {
-			controller.endpointsStore.Add(endpoint)
+		if req.Method == "POST" || req.Method == "PUT" {
+			if blockUpdate != nil {
+				go func() {
+					// Delay the update of endpoints to make endpoints cache out of sync
+					<-blockUpdate
+					_ = controller.endpointsStore.Add(endpoint)
+				}()
+			} else {
+				_ = controller.endpointsStore.Add(endpoint)
+			}
 			blockNextAction <- struct{}{}
 		}
 
 		if req.Method == "DELETE" {
-			go func() {
-				// Delay the deletion of endoints to make endpoint cache out of sync
-				<-blockDelete
-				controller.endpointsStore.Delete(endpoint)
+			if blockDelete != nil {
+				go func() {
+					// Delay the deletion of endpoints to make endpoints cache out of sync
+					<-blockDelete
+					_ = controller.endpointsStore.Delete(endpoint)
+					controller.onEndpointsDelete(endpoint)
+				}()
+			} else {
+				_ = controller.endpointsStore.Delete(endpoint)
 				controller.onEndpointsDelete(endpoint)
-			}()
+			}
 			blockNextAction <- struct{}{}
 		}
 
+		res.Header().Set("Content-Type", "application/json")
 		res.WriteHeader(http.StatusOK)
-		res.Write([]byte(runtime.EncodeOrDie(clientscheme.Codecs.LegacyCodec(v1.SchemeGroupVersion), &v1.Endpoints{})))
+		_, _ = res.Write([]byte(runtime.EncodeOrDie(clientscheme.Codecs.LegacyCodec(v1.SchemeGroupVersion), endpoint)))
 	}
 
 	mux := http.NewServeMux()
@@ -2378,7 +2392,7 @@ func TestMultipleServiceChanges(t *testing.T) {
 	blockDelete := make(chan struct{})
 	blockNextAction := make(chan struct{})
 	stopChan := make(chan struct{})
-	testServer := makeBlockingEndpointDeleteTestServer(t, controller, endpoint, blockDelete, blockNextAction, ns)
+	testServer := makeBlockingEndpointTestServer(t, controller, endpoint, nil, blockDelete, blockNextAction, ns)
 	defer testServer.Close()
 
 	tCtx := ktesting.Init(t)
@@ -2423,6 +2437,83 @@ func TestMultipleServiceChanges(t *testing.T) {
 	close(stopChan)
 }
 
+// TestMultiplePodChanges tests that endpoints that are not updated because of an out of sync endpoints cache are
+// eventually resynced after multiple Pod changes.
+func TestMultiplePodChanges(t *testing.T) {
+	ns := metav1.NamespaceDefault
+
+	readyEndpoints := &v1.Endpoints{
+		ObjectMeta: metav1.ObjectMeta{Name: "foo", Namespace: ns, ResourceVersion: "1"},
+		Subsets: []v1.EndpointSubset{{
+			Addresses: []v1.EndpointAddress{
+				{IP: "1.2.3.4", NodeName: &emptyNodeName, TargetRef: &v1.ObjectReference{Kind: "Pod", Name: "pod0", Namespace: ns}},
+			},
+			Ports: []v1.EndpointPort{{Port: 8080, Protocol: v1.ProtocolTCP}},
+		}},
+	}
+	notReadyEndpoints := &v1.Endpoints{
+		ObjectMeta: metav1.ObjectMeta{Name: "foo", Namespace: ns, ResourceVersion: "2"},
+		Subsets: []v1.EndpointSubset{{
+			NotReadyAddresses: []v1.EndpointAddress{
+				{IP: "1.2.3.4", NodeName: &emptyNodeName, TargetRef: &v1.ObjectReference{Kind: "Pod", Name: "pod0", Namespace: ns}},
+			},
+			Ports: []v1.EndpointPort{{Port: 8080, Protocol: v1.ProtocolTCP}},
+		}},
+	}
+
+	controller := &endpointController{}
+	blockUpdate := make(chan struct{})
+	blockNextAction := make(chan struct{})
+	stopChan := make(chan struct{})
+	testServer := makeBlockingEndpointTestServer(t, controller, notReadyEndpoints, blockUpdate, nil, blockNextAction, ns)
+	defer testServer.Close()
+
+	tCtx := ktesting.Init(t)
+	*controller = *newController(tCtx, testServer.URL, 0*time.Second)
+	pod := testPod(ns, 0, 1, true, ipv4only)
+	_ = controller.podStore.Add(pod)
+	_ = controller.endpointsStore.Add(readyEndpoints)
+	_ = controller.serviceStore.Add(&v1.Service{
+		ObjectMeta: metav1.ObjectMeta{Name: "foo", Namespace: ns},
+		Spec: v1.ServiceSpec{
+			Selector:  map[string]string{"foo": "bar"},
+			ClusterIP: "10.0.0.1",
+			Ports:     []v1.ServicePort{{Port: 80, Protocol: "TCP", TargetPort: intstr.FromInt32(8080)}},
+		},
+	})
+
+	go func() { controller.Run(tCtx, 1) }()
+
+	// Rapidly update the Pod: Ready -> NotReady -> Ready.
+	pod2 := pod.DeepCopy()
+	pod2.ResourceVersion = "2"
+	pod2.Status.Conditions[0].Status = v1.ConditionFalse
+	_ = controller.podStore.Update(pod2)
+	controller.updatePod(pod, pod2)
+	// blockNextAction should eventually unblock once server gets endpoints request.
+	waitForChanReceive(t, 1*time.Second, blockNextAction, "Pod Update should have caused a request to be sent to the test server")
+	// The endpoints update hasn't been applied to the cache yet.
+	pod3 := pod.DeepCopy()
+	pod3.ResourceVersion = "3"
+	pod3.Status.Conditions[0].Status = v1.ConditionTrue
+	_ = controller.podStore.Update(pod3)
+	controller.updatePod(pod2, pod3)
+	// It shouldn't get endpoints request as the endpoints in the cache is out-of-date.
+	timer := time.NewTimer(100 * time.Millisecond)
+	select {
+	case <-timer.C:
+	case <-blockNextAction:
+		t.Errorf("Pod Update shouldn't have caused a request to be sent to the test server")
+	}
+
+	// Applying the endpoints update to the cache should cause test server to update endpoints.
+	close(blockUpdate)
+	waitForChanReceive(t, 1*time.Second, blockNextAction, "Endpoints should have been updated")
+
+	close(blockNextAction)
+	close(stopChan)
+}
+
 func TestSyncServiceAddresses(t *testing.T) {
 	makeService := func(tolerateUnready bool) *v1.Service {
 		return &v1.Service{

pkg/controller/endpoint/endpoints_tracker.go

@@ -0,0 +1,64 @@
+/*
+Copyright 2024 The Kubernetes 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 endpoint
+
+import (
+	"sync"
+
+	v1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/types"
+)
+
+// staleEndpointsTracker tracks Endpoints and their stale resource versions to
+// help determine if an Endpoints is stale.
+type staleEndpointsTracker struct {
+	// lock protects staleResourceVersionByEndpoints.
+	lock sync.RWMutex
+	// staleResourceVersionByEndpoints tracks the stale resource version of Endpoints.
+	staleResourceVersionByEndpoints map[types.NamespacedName]string
+}
+
+func newStaleEndpointsTracker() *staleEndpointsTracker {
+	return &staleEndpointsTracker{
+		staleResourceVersionByEndpoints: map[types.NamespacedName]string{},
+	}
+}
+
+func (t *staleEndpointsTracker) Stale(endpoints *v1.Endpoints) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+	nn := types.NamespacedName{Name: endpoints.Name, Namespace: endpoints.Namespace}
+	t.staleResourceVersionByEndpoints[nn] = endpoints.ResourceVersion
+}
+
+func (t *staleEndpointsTracker) IsStale(endpoints *v1.Endpoints) bool {
+	t.lock.RLock()
+	defer t.lock.RUnlock()
+	nn := types.NamespacedName{Name: endpoints.Name, Namespace: endpoints.Namespace}
+	staleResourceVersion, exists := t.staleResourceVersionByEndpoints[nn]
+	if exists && staleResourceVersion == endpoints.ResourceVersion {
+		return true
+	}
+	return false
+}
+
+func (t *staleEndpointsTracker) Delete(namespace, name string) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+	nn := types.NamespacedName{Namespace: namespace, Name: name}
+	delete(t.staleResourceVersionByEndpoints, nn)
+}

pkg/controller/endpoint/endpoints_tracker_test.go

@@ -0,0 +1,54 @@
+/*
+Copyright 2024 The Kubernetes 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 endpoint
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	v1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+func TestStaleEndpointsTracker(t *testing.T) {
+	ns := metav1.NamespaceDefault
+	tracker := newStaleEndpointsTracker()
+
+	endpoints := &v1.Endpoints{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:            "foo",
+			Namespace:       ns,
+			ResourceVersion: "1",
+		},
+		Subsets: []v1.EndpointSubset{{
+			Addresses: []v1.EndpointAddress{{IP: "6.7.8.9", NodeName: &emptyNodeName}},
+			Ports:     []v1.EndpointPort{{Port: 1000}},
+		}},
+	}
+
+	assert.False(t, tracker.IsStale(endpoints), "IsStale should return false before the endpoint is staled")
+
+	tracker.Stale(endpoints)
+	assert.True(t, tracker.IsStale(endpoints), "IsStale should return true after the endpoint is staled")
+
+	endpoints.ResourceVersion = "2"
+	assert.False(t, tracker.IsStale(endpoints), "IsStale should return false after the endpoint is updated")
+
+	tracker.Delete(endpoints.Namespace, endpoints.Name)
+	assert.Empty(t, tracker.staleResourceVersionByEndpoints)
+}