apf: handle error from PollImmediateUntil

We should not attempt creation of mandatory objects if ensuring
the suggested configuration resulted in an error.
We rely on the presence of the "exempt" priority level configuration
object in the cluster to indicate whether we should ensure
suggested configuration.

pkg/registry/flowcontrol/rest/storage_flowcontrol.go

@@ -100,7 +100,7 @@ func (p RESTStorageProvider) PostStartHook() (string, genericapiserver.PostStart
 		flowcontrolClientSet := flowcontrolclient.NewForConfigOrDie(hookContext.LoopbackClientConfig)
 		go func() {
 			const retryCreatingSuggestedSettingsInterval = time.Second
-			_ = wait.PollImmediateUntil(
+			err := wait.PollImmediateUntil(
 				retryCreatingSuggestedSettingsInterval,
 				func() (bool, error) {
 					should, err := shouldEnsureSuggested(flowcontrolClientSet)
@@ -122,14 +122,25 @@ func (p RESTStorageProvider) PostStartHook() (string, genericapiserver.PostStart
 					return true, nil
 				},
 				hookContext.StopCh)
+			if err != nil {
+				klog.ErrorS(err, "Ensuring suggested configuration failed")
+
+				// We should not attempt creation of mandatory objects if ensuring the suggested
+				// configuration resulted in an error.
+				// This only happens when the stop channel is closed.
+				// We rely on the presence of the "exempt" priority level configuration object in the cluster
+				// to indicate whether we should ensure suggested configuration.
+				return
+			}
+
 			const retryCreatingMandatorySettingsInterval = time.Minute
 			_ = wait.PollImmediateUntil(
 				retryCreatingMandatorySettingsInterval,
 				func() (bool, error) {
 					if err := upgrade(
 						flowcontrolClientSet,
 						flowcontrolbootstrap.MandatoryFlowSchemas,
-						// Note: the "exempt" priority-level is supposed tobe the last item in the pre-defined
+						// Note: the "exempt" priority-level is supposed to be the last item in the pre-defined
 						// list, so that a crash in the midst of the first kube-apiserver startup does not prevent
 						// the full initial set of objects from being created.
 						flowcontrolbootstrap.MandatoryPriorityLevelConfigurations,