Merge pull request #30090 from mtaufen/dynamic-kubelet-restart

Automatic merge from submit-queue

[Kubelet] Optionally consume configuration from <node-name> named config maps

This extends the Kubelet to check the API server for new node-specific config, and exit when it finds said new config.

/cc @kubernetes/sig-node @mikedanese @timstclair @vishh

**Release note**:
```
Extends Kubelet with Alpha Dynamic Kubelet Configuration. Please note that this alpha feature does not currently work with cloud provider auto-detection.
```

pkg/util/config/feature_gate.go

@@ -38,14 +38,16 @@ const (
 	// specification of gates. Examples:
 	//   AllAlpha=false,NewFeature=true  will result in newFeature=true
 	//   AllAlpha=true,NewFeature=false  will result in newFeature=false
-	allAlphaGate = "AllAlpha"
+	allAlphaGate         = "AllAlpha"
+	dynamicKubeletConfig = "DynamicKubeletConfig"
 )
 
 var (
 	// Default values for recorded features.  Every new feature gate should be
 	// represented here.
 	knownFeatures = map[string]featureSpec{
-		allAlphaGate: {false, alpha},
+		allAlphaGate:         {false, alpha},
+		dynamicKubeletConfig: {false, alpha},
 	}
 
 	// Special handling for a few gates.
@@ -86,6 +88,7 @@ type FeatureGate interface {
 	// MyFeature() bool
 
 	// TODO: Define accessors for each non-API alpha feature.
+	DynamicKubeletConfig() bool
 }
 
 // featureGate implements FeatureGate as well as pflag.Value for flag parsing.
@@ -154,6 +157,11 @@ func (f *featureGate) Type() string {
 	return "mapStringBool"
 }
 
+// DynamicKubeletConfig returns value for dynamicKubeletConfig
+func (f *featureGate) DynamicKubeletConfig() bool {
+	return f.lookup(dynamicKubeletConfig)
+}
+
 func (f *featureGate) lookup(key string) bool {
 	defaultValue := f.known[key].enabled
 	if f.enabled != nil {