[release-4.19] OCPBUGS-56263: scope MCD node listers to current node

cmd/machine-config-daemon/start.go

@@ -153,16 +153,18 @@ func runStartCmd(_ *cobra.Command, _ []string) {
 	if startOpts.hypershiftDesiredConfigMap != "" {
 		// This is a hypershift-mode daemon
 		ctx := ctrlcommon.CreateControllerContext(ctx, cb)
+		nodeScopedInformer, nodeScopedInformerStartFunc := ctrlcommon.NewScopedNodeInformerFromClientBuilder(cb, startOpts.nodeName)
 		err := dn.HypershiftConnect(
 			startOpts.nodeName,
 			kubeClient,
-			ctx.KubeInformerFactory.Core().V1().Nodes(),
+			nodeScopedInformer,
 			startOpts.hypershiftDesiredConfigMap,
 		)
 		if err != nil {
 			ctrlcommon.WriteTerminationError(err)
 		}
 
+		nodeScopedInformerStartFunc(stopCh)
 		ctx.KubeInformerFactory.Start(stopCh)
 		close(ctx.InformersStarted)
 
@@ -177,14 +179,16 @@ func runStartCmd(_ *cobra.Command, _ []string) {
 
 	ctrlctx := ctrlcommon.CreateControllerContext(ctx, cb)
 
+	nodeScopedInformer, nodeScopedInformerStartFunc := ctrlcommon.NewScopedNodeInformerFromClientBuilder(cb, startOpts.nodeName)
+
 	// create the daemon instance. this also initializes kube client items
 	// which need to come from the container and not the chroot.
 	err = dn.ClusterConnect(
 		startOpts.nodeName,
 		kubeClient,
 		ctrlctx.ClientBuilder.MachineConfigClientOrDie(componentName),
 		ctrlctx.InformerFactory.Machineconfiguration().V1().MachineConfigs(),
-		ctrlctx.KubeInformerFactory.Core().V1().Nodes(),
+		nodeScopedInformer,
 		ctrlctx.InformerFactory.Machineconfiguration().V1().ControllerConfigs(),
 		ctrlctx.InformerFactory.Machineconfiguration().V1().MachineConfigPools(),
 		ctrlctx.ClientBuilder.OperatorClientOrDie(componentName),
@@ -202,6 +206,7 @@ func runStartCmd(_ *cobra.Command, _ []string) {
 	ctrlctx.KubeNamespacedInformerFactory.Start(stopCh)
 	ctrlctx.InformerFactory.Start(stopCh)
 	ctrlctx.OperatorInformerFactory.Start(stopCh)
+	nodeScopedInformerStartFunc(ctrlctx.Stop)
 	close(ctrlctx.InformersStarted)
 
 	select {
@@ -226,7 +231,7 @@ func runStartCmd(_ *cobra.Command, _ []string) {
 					criClient,
 					ctrlctx.ClientBuilder.MachineConfigClientOrDie(componentName),
 					ctrlctx.InformerFactory.Machineconfiguration().V1().PinnedImageSets(),
-					ctrlctx.KubeInformerFactory.Core().V1().Nodes(),
+					nodeScopedInformer,
 					ctrlctx.InformerFactory.Machineconfiguration().V1().MachineConfigPools(),
 					resource.MustParse(constants.MinFreeStorageAfterPrefetch),
 					constants.DefaultCRIOSocketPath,

pkg/controller/common/controller_context.go

@@ -22,6 +22,8 @@ import (
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/client-go/informers"
+	corev1informers "k8s.io/client-go/informers/core/v1"
+	"k8s.io/client-go/kubernetes"
 	"k8s.io/klog/v2"
 	"k8s.io/utils/clock"
 )
@@ -162,3 +164,33 @@ func CreateControllerContext(ctx context.Context, cb *clients.Builder) *Controll
 		RouteInformerFactory:                                routeSharedInformer,
 	}
 }
+
+// Creates a NodeInformer that is bound to a single node. This is for use by
+// the MCD to ensure that the MCD only receives watch events for the node that
+// it is running on as opposed to all cluster nodes. Doing this helps reduce
+// the load on the apiserver. Because the filters are applied to *all*
+// informers constructed by the informer factory, we want to ensure that this
+// factory is only used to construct a NodeInformer.
+//
+// Therefore, to ensure that this informer factory is only used for
+// constructing a NodeInformer with this specific filter, we only return the
+// instantiated NodeInformer instance and a start function.
+func NewScopedNodeInformer(kubeclient kubernetes.Interface, nodeName string) (corev1informers.NodeInformer, func(<-chan struct{})) {
+	sif := informers.NewSharedInformerFactoryWithOptions(
+		kubeclient,
+		resyncPeriod()(),
+		informers.WithTweakListOptions(func(opts *metav1.ListOptions) {
+			opts.FieldSelector = fields.OneTermEqualSelector("metadata.name", nodeName).String()
+		}),
+	)
+
+	return sif.Core().V1().Nodes(), sif.Start
+}
+
+// Creates a scoped node informer that is bound to a single node from a
+// clients.Builder instance. It sets the user-agent for the client to
+// node-scoped-informer before instantiating the node informer. Returns the
+// instantiated NodeInformer and a start function.
+func NewScopedNodeInformerFromClientBuilder(cb *clients.Builder, nodeName string) (corev1informers.NodeInformer, func(<-chan struct{})) {
+	return NewScopedNodeInformer(cb.KubeClientOrDie("node-scoped-informer"), nodeName)
+}

pkg/daemon/writer.go

@@ -8,7 +8,6 @@ import (
 
 	"k8s.io/client-go/tools/cache"
 
-	"k8s.io/client-go/informers"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
@@ -86,10 +85,16 @@ func newNodeWriter(nodeName string, stopCh <-chan struct{}) (NodeWriter, error)
 	}
 
 	klog.Infof("NodeWriter initialized with credentials from %s", nodeWriterKubeconfigPath)
-	informer := informers.NewSharedInformerFactory(kubeClient, ctrlcommon.DefaultResyncPeriod()())
-	nodeInformer := informer.Core().V1().Nodes()
-	nodeLister := nodeInformer.Lister()
-	nodeListerSynced := nodeInformer.Informer().HasSynced
+	// This informer needs to use the a different service account than the rest
+	// of the MCD, which is bound to the machine-config-daemon service account.
+	// Consequently, it must use a different informer factory than the parent
+	// informer factory. However, we can instantiate both that informer factory
+	// and the node informer in the same way that we instantiate the MCD
+	// informer.
+	informer, startFunc := ctrlcommon.NewScopedNodeInformer(kubeClient, nodeName)
+	nodeInformer := informer.Informer()
+	nodeLister := informer.Lister()
+	nodeListerSynced := nodeInformer.HasSynced
 
 	eventBroadcaster := record.NewBroadcaster()
 	eventBroadcaster.StartLogging(klog.V(2).Infof)
@@ -105,12 +110,12 @@ func newNodeWriter(nodeName string, stopCh <-chan struct{}) (NodeWriter, error)
 		kubeClient:       kubeClient,
 	}
 
-	nodeInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
+	nodeInformer.AddEventHandler(cache.ResourceEventHandlerFuncs{
 		AddFunc:    nw.handleNodeWriterEvent,
 		UpdateFunc: func(_, newObj interface{}) { nw.handleNodeWriterEvent(newObj) },
 	})
 
-	informer.Start(stopCh)
+	startFunc(stopCh)
 
 	return nw, nil
 }