Implement KEP-3458

staging/src/k8s.io/cloud-provider/controllers/service/controller.go

@@ -29,6 +29,7 @@ import (
 	"k8s.io/apimachinery/pkg/util/runtime"
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apimachinery/pkg/util/wait"
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	coreinformers "k8s.io/client-go/informers/core/v1"
 	clientset "k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/kubernetes/scheme"
@@ -41,6 +42,7 @@ import (
 	servicehelper "k8s.io/cloud-provider/service/helpers"
 	"k8s.io/component-base/featuregate"
 	controllersmetrics "k8s.io/component-base/metrics/prometheus/controllers"
+	"k8s.io/controller-manager/pkg/features"
 	"k8s.io/klog/v2"
 )
 
@@ -658,6 +660,12 @@ func nodeNames(nodes []*v1.Node) sets.String {
 }
 
 func shouldSyncUpdatedNode(oldNode, newNode *v1.Node) bool {
+	if utilfeature.DefaultFeatureGate.Enabled(features.StableLoadBalancerNodeSet) {
+		// Only Nodes with changes to the label
+		// "node.kubernetes.io/exclude-from-external-load-balancers" will
+		// trigger a load balancer re-sync.
+		return respectsPredicates(oldNode, nodeIncludedPredicate) != respectsPredicates(newNode, nodeIncludedPredicate)
+	}
 	// Evaluate the individual node exclusion predicate before evaluating the
 	// compounded result of all predicates. We don't sync ETP=local services
 	// for changes on the readiness condition, hence if a node remains NotReady
@@ -932,9 +940,21 @@ var (
 		nodeIncludedPredicate,
 		nodeUnTaintedPredicate,
 	}
+	stableNodeSetPredicates []NodeConditionPredicate = []NodeConditionPredicate{
+		nodeIncludedPredicate,
+		// This is not perfect, but probably good enough. We won't update the
+		// LBs just because the taint was added (see shouldSyncUpdatedNode) but
+		// if any other situation causes an LB sync, tainted nodes will be
+		// excluded at that time and cause connections on said node to not
+		// connection drain.
+		nodeUnTaintedPredicate,
+	}
 )
 
 func getNodePredicatesForService(service *v1.Service) []NodeConditionPredicate {
+	if utilfeature.DefaultFeatureGate.Enabled(features.StableLoadBalancerNodeSet) {
+		return stableNodeSetPredicates
+	}
 	if service.Spec.ExternalTrafficPolicy == v1.ServiceExternalTrafficPolicyLocal {
 		return etpLocalNodePredicates
 	}