UPSTREAM: <carry>: introduce delay in the post-start hooks

Author: jacobsee

pkg/controlplane/apiserver/server.go

@@ -320,6 +320,15 @@ func (c completedConfig) New(name string, delegationTarget genericapiserver.Dele
 		s.GenericAPIServer.AddPostStartHookOrDie("storage-readiness", s.GenericAPIServer.StorageReadinessHook.Hook)
 	}
 
+	// Simulate an additional readiness delay like we have on 1.36 (where WatchCacheInitializationPostStartHook defaults to true).
+	s.GenericAPIServer.AddPostStartHookOrDie("prove-pre-ready-window", func(hookContext genericapiserver.PostStartHookContext) error {
+		select {
+		case <-time.After(15 * time.Second):
+		case <-hookContext.Done():
+		}
+		return nil
+	})
+
 	s.GenericAPIServer.AddPostStartHookOrDie("start-legacy-token-tracking-controller", func(hookContext genericapiserver.PostStartHookContext) error {
 		go legacytokentracking.NewController(client).RunWithContext(hookContext)
 		return nil