nfd-master: proper shutdown of nfd api informers

Ensure that the nfd API informer factory is properly shut down and all
resources released when stop() is called.

This eliminates memory leaks on re-configure events when leader election
is enabled.

pkg/nfd-master/nfd-api-controller.go

@@ -36,6 +36,7 @@ import (
 )
 
 type nfdController struct {
+	factory            nfdinformers.SharedInformerFactory
 	featureLister      nfdlisters.NodeFeatureLister
 	ruleLister         nfdlisters.NodeFeatureRuleLister
 	featureGroupLister nfdlisters.NodeFeatureGroupLister
@@ -181,12 +182,35 @@ func newNfdController(config *restclient.Config, nfdApiControllerOptions nfdApiC
 	}
 
 	klog.InfoS("informer caches synced", "duration", time.Since(now))
+	c.factory = informerFactory
 
 	return c, nil
 }
 
+func readChUntilClosed[T any](ch <-chan T) {
+	for {
+		if _, ok := <-ch; !ok {
+			return
+		}
+	}
+}
+
 func (c *nfdController) stop() {
 	close(c.stopChan)
+
+	// Make sure that there are no blocking event handler callbacks and all
+	// channels are closed.
+	// NOTE: This will be unnecessary and could be removed if/when the dynamic
+	// run-time configuration is dropped.
+	go readChUntilClosed(c.updateOneNodeChan)
+	go readChUntilClosed(c.updateAllNodesChan)
+	go readChUntilClosed(c.updateNodeFeatureGroupChan)
+	go readChUntilClosed(c.updateAllNodeFeatureGroupsChan)
+	c.factory.Shutdown()
+	close(c.updateOneNodeChan)
+	close(c.updateAllNodesChan)
+	close(c.updateNodeFeatureGroupChan)
+	close(c.updateAllNodeFeatureGroupsChan)
 }
 
 func getNodeNameForObj(obj metav1.Object) (string, error) {

pkg/nfd-master/nfd-master.go

@@ -392,7 +392,7 @@ func (m *nfdMaster) Run() error {
 
 			// Update all nodes when the configuration changes
 			if m.nfdController != nil && nfdfeatures.NFDFeatureGate.Enabled(nfdfeatures.NodeFeatureAPI) {
-				m.nfdController.updateAllNodesChan <- struct{}{}
+				m.nfdController.updateAllNodes()
 			}
 
 		case <-m.stop: