Stop exposing list-via-watch from the server

With StreamingCollectionEncodingToJSON and
StreamingCollectionEncodingToProtobuf, the WatchList must re-justify its
necessity.  To prevent an ecosystem from building around a feature that
may not be promoted, we will stop serving list-via-watch until
performance numbers can justify its inclusion.

This also stops the kube-controller-manager from using the
list-via-watch by default.  The fallback is a regular list, so during
the skew during an upgrade the "right" thing will happen and the new
StreamingCollectionEncoding will be used.

Author: deads2k

cmd/kube-controller-manager/app/options/options.go

@@ -27,7 +27,6 @@ import (
 	apiserveroptions "k8s.io/apiserver/pkg/server/options"
 	"k8s.io/apiserver/pkg/util/compatibility"
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
-	clientgofeaturegate "k8s.io/client-go/features"
 	clientset "k8s.io/client-go/kubernetes"
 	clientgokubescheme "k8s.io/client-go/kubernetes/scheme"
 	restclient "k8s.io/client-go/rest"
@@ -38,13 +37,11 @@ import (
 	cpoptions "k8s.io/cloud-provider/options"
 	cliflag "k8s.io/component-base/cli/flag"
 	basecompatibility "k8s.io/component-base/compatibility"
-	"k8s.io/component-base/featuregate"
 	"k8s.io/component-base/logs"
 	logsapi "k8s.io/component-base/logs/api/v1"
 	"k8s.io/component-base/metrics"
 	"k8s.io/component-base/zpages/flagz"
 	cmoptions "k8s.io/controller-manager/options"
-	"k8s.io/klog/v2"
 	kubectrlmgrconfigv1alpha1 "k8s.io/kube-controller-manager/config/v1alpha1"
 	kubecontrollerconfig "k8s.io/kubernetes/cmd/kube-controller-manager/app/config"
 	"k8s.io/kubernetes/cmd/kube-controller-manager/names"
@@ -297,15 +294,6 @@ func (s *KubeControllerManagerOptions) Flags(allControllers []string, disabledBy
 	fs.StringVar(&s.Master, "master", s.Master, "The address of the Kubernetes API server (overrides any value in kubeconfig).")
 	fs.StringVar(&s.Generic.ClientConnection.Kubeconfig, "kubeconfig", s.Generic.ClientConnection.Kubeconfig, "Path to kubeconfig file with authorization and master location information (the master location can be overridden by the master flag).")
 
-	if !utilfeature.DefaultFeatureGate.Enabled(featuregate.Feature(clientgofeaturegate.WatchListClient)) {
-		if err := utilfeature.DefaultMutableFeatureGate.OverrideDefault(featuregate.Feature(clientgofeaturegate.WatchListClient), true); err != nil {
-			// it turns out that there are some integration tests that start multiple control plane components which
-			// share global DefaultFeatureGate/DefaultMutableFeatureGate variables.
-			// in those cases, the above call will fail (FG already registered and cannot be overridden), and the error will be logged.
-			klog.Errorf("unable to set %s feature gate, err: %v", clientgofeaturegate.WatchListClient, err)
-		}
-	}
-
 	s.ComponentGlobalsRegistry.AddFlags(fss.FlagSet("generic"))
 
 	return fss

cmd/kube-controller-manager/app/options/options_test.go

@@ -1469,6 +1469,8 @@ func TestControllerManagerAliases(t *testing.T) {
 }
 
 func TestWatchListClientFlagUsage(t *testing.T) {
+	t.Skip("skip this test until we either bring back WatchListClient or remove it")
+
 	fs := pflag.NewFlagSet("addflagstest", pflag.ContinueOnError)
 	s, _ := NewKubeControllerManagerOptions()
 	for _, f := range s.Flags([]string{""}, []string{""}, nil).FlagSets {
@@ -1480,6 +1482,8 @@ func TestWatchListClientFlagUsage(t *testing.T) {
 }
 
 func TestWatchListClientFlagChange(t *testing.T) {
+	t.Skip("skip this test until we either bring back WatchListClient or remove it")
+
 	fs := pflag.NewFlagSet("addflagstest", pflag.ContinueOnError)
 	s, err := NewKubeControllerManagerOptions()
 	if err != nil {

pkg/features/kube_features.go

@@ -1339,6 +1339,8 @@ var defaultVersionedKubernetesFeatureGates = map[featuregate.Feature]featuregate
 	genericfeatures.WatchList: {
 		{Version: version.MustParse("1.27"), Default: false, PreRelease: featuregate.Alpha},
 		{Version: version.MustParse("1.32"), Default: true, PreRelease: featuregate.Beta},
+		// switch this back to false because the json and proto streaming encoders appear to work better.
+		{Version: version.MustParse("1.33"), Default: false, PreRelease: featuregate.Beta},
 	},
 
 	GitRepoVolumeDriver: {

staging/src/k8s.io/apiserver/pkg/features/kube_features.go

@@ -415,5 +415,7 @@ var defaultVersionedKubernetesFeatureGates = map[featuregate.Feature]featuregate
 	WatchList: {
 		{Version: version.MustParse("1.27"), Default: false, PreRelease: featuregate.Alpha},
 		{Version: version.MustParse("1.32"), Default: true, PreRelease: featuregate.Beta},
+		// switch this back to false because the json and proto streaming encoders appear to work better.
+		{Version: version.MustParse("1.33"), Default: false, PreRelease: featuregate.Beta},
 	},
 }

test/compatibility_lifecycle/reference/versioned_feature_list.yaml

@@ -1687,6 +1687,10 @@
     lockToDefault: false
     preRelease: Beta
     version: "1.32"
+  - default: false
+    lockToDefault: false
+    preRelease: Beta
+    version: "1.33"
 - name: WindowsCPUAndMemoryAffinity
   versionedSpecs:
   - default: false