k8s: delete IPs from ipcache for no running Pods

[ upstream commit b3adc4d ]

In Kubernetes, a Job creates a pod which will complete with either
the "Succeeded" or "Failed" PodPhase. Kubernetes will leave these
Pods around until the Job is deleted by the operator. As soon the pod
enters either one of the previously described PodPhases, Kubelet will
send a CNI delete event to Cilium agent which will then release the
allocated IP addresses of that pod, making the IP address available
again.

If not disabled, Cilium will create a Cilium Endpoint for each Pod in
the cluster that has its network managed by Cilium.

Cilium agent populates the ipcache with the information retrieved from
Pods and Cilium Endpoints events, in case of duplicated information,
ipcache will be stored with the state from Cilium Endpoints.

In a unlikely case of Cilium agent not running and the Pod enters the
"Succeeded" state, it will mean the Cilium agent will not be available
to delete the Cilium Endpoint created for that Pod.

To complement this fix, Cilium agents will also prune Cilium Endpoints
of not running pods on start up.

Signed-off-by: André Martins <andre@cilium.io>

operator/k8s_cep_gc.go

@@ -16,12 +16,15 @@ package main
 
 import (
 	"context"
+	"time"
 
 	operatorOption "github.com/cilium/cilium/operator/option"
 	"github.com/cilium/cilium/operator/watchers"
 	"github.com/cilium/cilium/pkg/controller"
 	"github.com/cilium/cilium/pkg/k8s"
 	cilium_v2 "github.com/cilium/cilium/pkg/k8s/apis/cilium.io/v2"
+	slim_corev1 "github.com/cilium/cilium/pkg/k8s/slim/k8s/apis/core/v1"
+	k8sUtils "github.com/cilium/cilium/pkg/k8s/utils"
 	"github.com/cilium/cilium/pkg/logging/logfields"
 
 	"github.com/sirupsen/logrus"
@@ -38,24 +41,37 @@ import (
 //   - for each CEP
 //       delete CEP if the corresponding pod does not exist
 // CiliumEndpoint objects have the same name as the pod they represent
-func enableCiliumEndpointSyncGC() {
+func enableCiliumEndpointSyncGC(once bool) {
 	var (
 		controllerName = "to-k8s-ciliumendpoint-gc"
 		scopedLog      = log.WithField("controller", controllerName)
+		gcInterval     time.Duration
+		stopCh         = make(chan struct{})
 	)
 
-	log.Info("Starting to garbage collect stale CiliumEndpoint custom resources...")
-
 	ciliumClient := ciliumK8sClient.CiliumV2()
 
+	if once {
+		log.Info("Running the garbage collector only once to clean up leftover CiliumEndpoint custom resources...")
+		gcInterval = 0
+	} else {
+		log.Info("Starting to garbage collect stale CiliumEndpoint custom resources...")
+		gcInterval = operatorOption.Config.EndpointGCInterval
+	}
+
 	// This functions will block until the resources are synced with k8s.
-	watchers.CiliumEndpointsInit(ciliumClient)
-	watchers.PodsInit(k8s.WatcherCli())
+	watchers.CiliumEndpointsInit(ciliumClient, stopCh)
+	if !once {
+		// If we are running this function "once" it means that we
+		// will delete all CEPs in the cluster regardless of the pod
+		// state.
+		watchers.PodsInit(k8s.WatcherCli(), stopCh)
+	}
 
 	// this dummy manager is needed only to add this controller to the global list
 	controller.NewManager().UpdateController(controllerName,
 		controller.ControllerParams{
-			RunInterval: operatorOption.Config.EndpointGCInterval,
+			RunInterval: gcInterval,
 			DoFunc: func(ctx context.Context) error {
 				// For each CEP we fetched, check if we know about it
 				for _, cepObj := range watchers.CiliumEndpointStore.List() {
@@ -65,33 +81,60 @@ func enableCiliumEndpointSyncGC() {
 							Errorf("Saw %T object while expecting *cilium_v2.CiliumEndpoint", cepObj)
 						continue
 					}
-
 					cepFullName := cep.Namespace + "/" + cep.Name
-					_, exists, err := watchers.PodStore.GetByKey(cepFullName)
-					if err != nil {
-						scopedLog.WithError(err).Warn("Unable to get pod from store")
-						continue
-					}
-					if !exists {
-						// FIXME: this is fragile as we might have received the
-						// CEP notification first but not the pod notification
-						// so we need to have a similar mechanism that we have
-						// for the keep alive of security identities.
-						scopedLog = scopedLog.WithFields(logrus.Fields{
-							logfields.EndpointID: cep.Status.ID,
-							logfields.K8sPodName: cepFullName,
-						})
-						scopedLog.Debug("Orphaned CiliumEndpoint is being garbage collected")
-						PropagationPolicy := meta_v1.DeletePropagationBackground // because these are const strings but the API wants pointers
-						err := ciliumClient.CiliumEndpoints(cep.Namespace).Delete(
-							ctx,
-							cep.Name,
-							meta_v1.DeleteOptions{PropagationPolicy: &PropagationPolicy})
-						if !k8serrors.IsNotFound(err) {
-							scopedLog.WithError(err).Warning("Unable to delete orphaned CEP")
-							return err
+					scopedLog = scopedLog.WithFields(logrus.Fields{
+						logfields.K8sPodName: cepFullName,
+					})
+
+					// If we are running this function "once" it means that we
+					// will delete all CEPs in the cluster regardless of the pod
+					// state therefore we won't even watch for the pod store.
+					if !once {
+						podObj, exists, err := watchers.PodStore.GetByKey(cepFullName)
+						if err != nil {
+							scopedLog.WithError(err).Warn("Unable to get pod from store")
+							continue
+						}
+						if exists {
+							pod := podObj.(*slim_corev1.Pod)
+							if !ok {
+								log.WithField(logfields.Object, podObj).
+									Errorf("Saw %T object while expecting *slim_corev1.Pod", podObj)
+								continue
+							}
+							// In Kubernetes Jobs, Pods can be left in Kubernetes until the Job
+							// is deleted. If the Job is never deleted, Cilium will never receive a Pod
+							// delete event, causing the IP to be left in the ipcache.
+							// For this reason we should delete the ipcache entries whenever the pod
+							// status is either PodFailed or PodSucceeded as it means the IP address
+							// is no longer in use.
+							if k8sUtils.IsPodRunning(pod.Status) {
+								continue
+							}
 						}
 					}
+					// FIXME: this is fragile as we might have received the
+					// CEP notification first but not the pod notification
+					// so we need to have a similar mechanism that we have
+					// for the keep alive of security identities.
+					scopedLog = scopedLog.WithFields(logrus.Fields{
+						logfields.EndpointID: cep.Status.ID,
+					})
+					scopedLog.Debug("Orphaned CiliumEndpoint is being garbage collected")
+					PropagationPolicy := meta_v1.DeletePropagationBackground // because these are const strings but the API wants pointers
+					err := ciliumClient.CiliumEndpoints(cep.Namespace).Delete(
+						ctx,
+						cep.Name,
+						meta_v1.DeleteOptions{PropagationPolicy: &PropagationPolicy})
+					if !k8serrors.IsNotFound(err) {
+						scopedLog.WithError(err).Warning("Unable to delete orphaned CEP")
+						return err
+					}
+				}
+				// We have cleaned up all CEPs from Kubernetes so we can stop
+				// the k8s watchers.
+				if once {
+					close(stopCh)
 				}
 				return nil
 			},

operator/k8s_pod_controller.go

@@ -26,6 +26,7 @@ import (
 	slim_corev1 "github.com/cilium/cilium/pkg/k8s/slim/k8s/apis/core/v1"
 
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/util/wait"
 )
 
 const (
@@ -39,7 +40,7 @@ var (
 
 func enableUnmanagedKubeDNSController() {
 	// These functions will block until the resources are synced with k8s.
-	watchers.CiliumEndpointsInit(k8s.CiliumClient().CiliumV2())
+	watchers.CiliumEndpointsInit(k8s.CiliumClient().CiliumV2(), wait.NeverStop)
 	watchers.UnmanagedPodsInit(k8s.WatcherCli())
 
 	controller.NewManager().UpdateController("restart-unmanaged-kube-dns",

operator/main.go

@@ -458,7 +458,12 @@ func onOperatorStartLeading(ctx context.Context) {
 	}
 
 	if operatorOption.Config.EnableCEPGC && operatorOption.Config.EndpointGCInterval != 0 {
-		enableCiliumEndpointSyncGC()
+		enableCiliumEndpointSyncGC(false)
+	} else {
+		// Even if the EndpointGC is disabled we still want it to run at least
+		// once. This is to prevent leftover CEPs from populating ipcache with
+		// stale entries.
+		enableCiliumEndpointSyncGC(true)
 	}
 
 	err = enableCNPWatcher(apiextensionsK8sClient)

operator/watchers/cilium_endpoint.go

@@ -27,7 +27,6 @@ import (
 	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/fields"
-	"k8s.io/apimachinery/pkg/util/wait"
 	"k8s.io/client-go/tools/cache"
 )
 
@@ -67,7 +66,7 @@ func identityIndexFunc(obj interface{}) ([]string, error) {
 }
 
 // CiliumEndpointsInit starts a CiliumEndpointWatcher
-func CiliumEndpointsInit(ciliumNPClient cilium_cli.CiliumV2Interface) {
+func CiliumEndpointsInit(ciliumNPClient cilium_cli.CiliumV2Interface, stopCh <-chan struct{}) {
 	once.Do(func() {
 		CiliumEndpointStore = cache.NewIndexer(cache.DeletionHandlingMetaNamespaceKeyFunc, indexers)
 
@@ -80,9 +79,9 @@ func CiliumEndpointsInit(ciliumNPClient cilium_cli.CiliumV2Interface) {
 			convertToCiliumEndpoint,
 			CiliumEndpointStore,
 		)
-		go ciliumEndpointInformer.Run(wait.NeverStop)
+		go ciliumEndpointInformer.Run(stopCh)
 
-		cache.WaitForCacheSync(wait.NeverStop, ciliumEndpointInformer.HasSynced)
+		cache.WaitForCacheSync(stopCh, ciliumEndpointInformer.HasSynced)
 		close(CiliumEndpointsSynced)
 	})
 }

operator/watchers/pod.go

@@ -47,7 +47,7 @@ var (
 	UnmanagedPodStoreSynced = make(chan struct{})
 )
 
-func PodsInit(k8sClient kubernetes.Interface) {
+func PodsInit(k8sClient kubernetes.Interface, stopCh <-chan struct{}) {
 	var podInformer cache.Controller
 	PodStore, podInformer = informer.NewInformer(
 		cache.NewListWatchFromClient(k8sClient.CoreV1().RESTClient(),
@@ -57,9 +57,9 @@ func PodsInit(k8sClient kubernetes.Interface) {
 		cache.ResourceEventHandlerFuncs{},
 		convertToPod,
 	)
-	go podInformer.Run(wait.NeverStop)
+	go podInformer.Run(stopCh)
 
-	cache.WaitForCacheSync(wait.NeverStop, podInformer.HasSynced)
+	cache.WaitForCacheSync(stopCh, podInformer.HasSynced)
 	close(PodStoreSynced)
 }
 
@@ -76,6 +76,9 @@ func convertToPod(obj interface{}) interface{} {
 				Namespace:       concreteObj.Namespace,
 				ResourceVersion: concreteObj.ResourceVersion,
 			},
+			Status: slim_corev1.PodStatus{
+				Phase: concreteObj.Status.Phase,
+			},
 		}
 		*concreteObj = slim_corev1.Pod{}
 		return p
@@ -93,6 +96,9 @@ func convertToPod(obj interface{}) interface{} {
 					Namespace:       pod.Namespace,
 					ResourceVersion: pod.ResourceVersion,
 				},
+				Status: slim_corev1.PodStatus{
+					Phase: pod.Status.Phase,
+				},
 			},
 		}
 		// Small GC optimization

pkg/k8s/utils/utils.go

@@ -15,9 +15,11 @@
 package utils
 
 import (
+	slim_corev1 "github.com/cilium/cilium/pkg/k8s/slim/k8s/apis/core/v1"
 	"github.com/cilium/cilium/pkg/k8s/slim/k8s/apis/labels"
 	"github.com/cilium/cilium/pkg/k8s/slim/k8s/apis/selection"
 	"github.com/cilium/cilium/pkg/option"
+
 	v1 "k8s.io/api/core/v1"
 	v1meta "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
@@ -103,3 +105,14 @@ func GetServiceListOptionsModifier() (func(options *v1meta.ListOptions), error)
 		options.LabelSelector = labelSelector.String()
 	}, nil
 }
+
+// IsPodRunning returns true if the pod is considered to be in running state.
+// We consider a Running pod a pod that does not report a Failed nor a Succeeded
+// pod Phase.
+func IsPodRunning(status slim_corev1.PodStatus) bool {
+	switch status.Phase {
+	case slim_corev1.PodFailed, slim_corev1.PodSucceeded:
+		return false
+	}
+	return true
+}