Merge pull request #54485 from sttts/sttts-unify-admission-constructors

Automatic merge from submit-queue (batch tested with PRs 54761, 54748, 53991, 54485, 46951). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

admission: unify plugin constructors

It's common in Go to return the actual object in constructors, not **one interface**
it implements. This allows us to implement multiple interfaces, but only have
one constructor. As having private types in constructors, we export all plugin structs, of course with private fields.

Note: super interfaces do not work if there are overlapping methods.

Kubernetes-commit: 7a944a69d64841472347056c7b54c5b264bed17b

pkg/admission/chain.go

@@ -20,7 +20,7 @@ package admission
 type chainAdmissionHandler []Interface
 
 // NewChainHandler creates a new chain handler from an array of handlers. Used for testing.
-func NewChainHandler(handlers ...Interface) Interface {
+func NewChainHandler(handlers ...Interface) chainAdmissionHandler {
 	return chainAdmissionHandler(handlers)
 }
 

pkg/admission/plugin/initialization/initialization.go

@@ -74,6 +74,7 @@ func NewInitializer() admission.Interface {
 	return &initializer{}
 }
 
+// Validate implements the Validator interface.
 func (i *initializer) Validate() error {
 	if i.config == nil {
 		return fmt.Errorf("the Initializer admission plugin requires a Kubernetes client to be provided")
@@ -94,10 +95,12 @@ func (i *initializer) Validate() error {
 	return nil
 }
 
+// SetExternalKubeClientSet implements the WantsExternalKubeClientSet interface.
 func (i *initializer) SetExternalKubeClientSet(client clientset.Interface) {
 	i.config = configuration.NewInitializerConfigurationManager(client.Admissionregistration().InitializerConfigurations())
 }
 
+// SetAuthorizer implements the WantsAuthorizer interface.
 func (i *initializer) SetAuthorizer(a authorizer.Authorizer) {
 	i.authorizer = a
 }
@@ -276,6 +279,8 @@ func (i *initializer) canInitialize(a admission.Attributes, message string) erro
 	return nil
 }
 
+// Handles returns true if this admission controller can handle the given operation
+// where operation can be one of CREATE, UPDATE, DELETE, or CONNECT
 func (i *initializer) Handles(op admission.Operation) bool {
 	return op == admission.Create || op == admission.Update
 }

pkg/admission/plugin/namespace/lifecycle/admission.go

@@ -202,16 +202,19 @@ func newLifecycleWithClock(immortalNamespaces sets.String, clock utilcache.Clock
 	}, nil
 }
 
+// SetExternalKubeInformerFactory implements the WantsExternalKubeInformerFactory interface.
 func (l *lifecycle) SetExternalKubeInformerFactory(f informers.SharedInformerFactory) {
 	namespaceInformer := f.Core().V1().Namespaces()
 	l.namespaceLister = namespaceInformer.Lister()
 	l.SetReadyFunc(namespaceInformer.Informer().HasSynced)
 }
 
+// SetExternalKubeClientSet implements the WantsExternalKubeClientSet interface.
 func (l *lifecycle) SetExternalKubeClientSet(client kubernetes.Interface) {
 	l.client = client
 }
 
+// Validate implement the Validator interface.
 func (l *lifecycle) Validate() error {
 	if l.namespaceLister == nil {
 		return fmt.Errorf("missing namespaceLister")

pkg/admission/plugin/webhook/admission.go

@@ -151,10 +151,13 @@ func (a *GenericAdmissionWebhook) SetScheme(scheme *runtime.Scheme) {
 	}
 }
 
+// WantsExternalKubeClientSet defines a function which sets external ClientSet for admission plugins that need it
 func (a *GenericAdmissionWebhook) SetExternalKubeClientSet(client clientset.Interface) {
 	a.hookSource = configuration.NewExternalAdmissionHookConfigurationManager(client.Admissionregistration().ExternalAdmissionHookConfigurations())
 }
 
+// Validator holds Validate functions, which are responsible for validation of initialized shared resources
+// and should be implemented on admission plugins
 func (a *GenericAdmissionWebhook) Validate() error {
 	if a.hookSource == nil {
 		return fmt.Errorf("the GenericAdmissionWebhook admission plugin requires a Kubernetes client to be provided")