Deep disablement for APF based on --enable-priority-and-fairness.

Avoids starting informers or the config-consuming controller when
--enable-priority-and-fairness=false. For kube-apiserver, the config-producing controller runs if
and only if flowcontrol API storage is enabled.

Kubernetes-commit: 83f5b5c240e5cced1371bbd22e458dae43975238

pkg/server/options/feature.go

@@ -17,16 +17,24 @@ limitations under the License.
 package options
 
 import (
+	"fmt"
+
 	"github.com/spf13/pflag"
 
 	"k8s.io/apimachinery/pkg/runtime/serializer"
+	"k8s.io/apiserver/pkg/features"
 	"k8s.io/apiserver/pkg/server"
+	"k8s.io/apiserver/pkg/util/feature"
+	utilflowcontrol "k8s.io/apiserver/pkg/util/flowcontrol"
+	"k8s.io/client-go/informers"
+	"k8s.io/client-go/kubernetes"
 )
 
 type FeatureOptions struct {
 	EnableProfiling           bool
 	DebugSocketPath           string
 	EnableContentionProfiling bool
+	EnablePriorityAndFairness bool
 }
 
 func NewFeatureOptions() *FeatureOptions {
@@ -36,6 +44,7 @@ func NewFeatureOptions() *FeatureOptions {
 		EnableProfiling:           defaults.EnableProfiling,
 		DebugSocketPath:           defaults.DebugSocketPath,
 		EnableContentionProfiling: defaults.EnableContentionProfiling,
+		EnablePriorityAndFairness: true,
 	}
 }
 
@@ -50,9 +59,11 @@ func (o *FeatureOptions) AddFlags(fs *pflag.FlagSet) {
 		"Enable block profiling, if profiling is enabled")
 	fs.StringVar(&o.DebugSocketPath, "debug-socket-path", o.DebugSocketPath,
 		"Use an unprotected (no authn/authz) unix-domain socket for profiling with the given path")
+	fs.BoolVar(&o.EnablePriorityAndFairness, "enable-priority-and-fairness", o.EnablePriorityAndFairness, ""+
+		"If true and the APIPriorityAndFairness feature gate is enabled, replace the max-in-flight handler with an enhanced one that queues and dispatches with priority and fairness")
 }
 
-func (o *FeatureOptions) ApplyTo(c *server.Config) error {
+func (o *FeatureOptions) ApplyTo(c *server.Config, clientset kubernetes.Interface, informers informers.SharedInformerFactory) error {
 	if o == nil {
 		return nil
 	}
@@ -61,6 +72,18 @@ func (o *FeatureOptions) ApplyTo(c *server.Config) error {
 	c.DebugSocketPath = o.DebugSocketPath
 	c.EnableContentionProfiling = o.EnableContentionProfiling
 
+	if o.EnablePriorityAndFairness && feature.DefaultFeatureGate.Enabled(features.APIPriorityAndFairness) {
+		if c.MaxRequestsInFlight+c.MaxMutatingRequestsInFlight <= 0 {
+			return fmt.Errorf("invalid configuration: MaxRequestsInFlight=%d and MaxMutatingRequestsInFlight=%d; they must add up to something positive", c.MaxRequestsInFlight, c.MaxMutatingRequestsInFlight)
+
+		}
+		c.FlowControl = utilflowcontrol.New(
+			informers,
+			clientset.FlowcontrolV1beta3(),
+			c.MaxRequestsInFlight+c.MaxMutatingRequestsInFlight,
+		)
+	}
+
 	return nil
 }
 

pkg/server/options/recommended.go

@@ -17,20 +17,15 @@ limitations under the License.
 package options
 
 import (
-	"fmt"
-
 	"github.com/spf13/pflag"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apiserver/pkg/admission"
-	"k8s.io/apiserver/pkg/features"
 	"k8s.io/apiserver/pkg/server"
 	"k8s.io/apiserver/pkg/storage/storagebackend"
 	"k8s.io/apiserver/pkg/util/feature"
-	utilflowcontrol "k8s.io/apiserver/pkg/util/flowcontrol"
 	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/component-base/featuregate"
-	"k8s.io/klog/v2"
 )
 
 // RecommendedOptions contains the recommended options for running an API server.
@@ -122,17 +117,17 @@ func (o *RecommendedOptions) ApplyTo(config *server.RecommendedConfig) error {
 	if err := o.Audit.ApplyTo(&config.Config); err != nil {
 		return err
 	}
-	if err := o.Features.ApplyTo(&config.Config); err != nil {
-		return err
-	}
 	if err := o.CoreAPI.ApplyTo(config); err != nil {
 		return err
 	}
-	initializers, err := o.ExtraAdmissionInitializers(config)
+	kubeClient, err := kubernetes.NewForConfig(config.ClientConfig)
 	if err != nil {
 		return err
 	}
-	kubeClient, err := kubernetes.NewForConfig(config.ClientConfig)
+	if err := o.Features.ApplyTo(&config.Config, kubeClient, config.SharedInformerFactory); err != nil {
+		return err
+	}
+	initializers, err := o.ExtraAdmissionInitializers(config)
 	if err != nil {
 		return err
 	}
@@ -144,21 +139,6 @@ func (o *RecommendedOptions) ApplyTo(config *server.RecommendedConfig) error {
 		initializers...); err != nil {
 		return err
 	}
-	if feature.DefaultFeatureGate.Enabled(features.APIPriorityAndFairness) {
-		if config.ClientConfig != nil {
-			if config.MaxRequestsInFlight+config.MaxMutatingRequestsInFlight <= 0 {
-				return fmt.Errorf("invalid configuration: MaxRequestsInFlight=%d and MaxMutatingRequestsInFlight=%d; they must add up to something positive", config.MaxRequestsInFlight, config.MaxMutatingRequestsInFlight)
-
-			}
-			config.FlowControl = utilflowcontrol.New(
-				config.SharedInformerFactory,
-				kubernetes.NewForConfigOrDie(config.ClientConfig).FlowcontrolV1beta3(),
-				config.MaxRequestsInFlight+config.MaxMutatingRequestsInFlight,
-			)
-		} else {
-			klog.Warningf("Neither kubeconfig is provided nor service-account is mounted, so APIPriorityAndFairness will be disabled")
-		}
-	}
 	return nil
 }
 

pkg/server/options/server_run_options.go

@@ -62,8 +62,7 @@ type ServerRunOptions struct {
 	// decoded in a write request. 0 means no limit.
 	// We intentionally did not add a flag for this option. Users of the
 	// apiserver library can wire it to a flag.
-	MaxRequestBodyBytes       int64
-	EnablePriorityAndFairness bool
+	MaxRequestBodyBytes int64
 
 	// ShutdownSendRetryAfter dictates when to initiate shutdown of the HTTP
 	// Server during the graceful termination of the apiserver. If true, we wait
@@ -104,7 +103,6 @@ func NewServerRunOptions() *ServerRunOptions {
 		ShutdownWatchTerminationGracePeriod: defaults.ShutdownWatchTerminationGracePeriod,
 		JSONPatchMaxCopyBytes:               defaults.JSONPatchMaxCopyBytes,
 		MaxRequestBodyBytes:                 defaults.MaxRequestBodyBytes,
-		EnablePriorityAndFairness:           true,
 		ShutdownSendRetryAfter:              false,
 	}
 }
@@ -325,9 +323,6 @@ func (s *ServerRunOptions) AddUniversalFlags(fs *pflag.FlagSet) {
 		"handler, which picks a randomized value above this number as the connection timeout, "+
 		"to spread out load.")
 
-	fs.BoolVar(&s.EnablePriorityAndFairness, "enable-priority-and-fairness", s.EnablePriorityAndFairness, ""+
-		"If true and the APIPriorityAndFairness feature gate is enabled, replace the max-in-flight handler with an enhanced one that queues and dispatches with priority and fairness")
-
 	fs.DurationVar(&s.ShutdownDelayDuration, "shutdown-delay-duration", s.ShutdownDelayDuration, ""+
 		"Time to delay the termination. During that time the server keeps serving requests normally. The endpoints /healthz and /livez "+
 		"will return success, but /readyz immediately returns failure. Graceful termination starts after this delay "+