nfd-master: parse kubeconfig even with NoPublish set

Don't try to be too smart when kubeconfig is needed. In practice, the
nfd-master really doesn't work anymore (with the NodeFeature API
enabled) without a kubeconfig set. This patch fixes crashes happening
when NoPublish is enabled, e.g. in listing all nodes in the nfd api
handler and in getting single node objects in the node updater pool.

pkg/nfd-master/nfd-master-internal_test.go

@@ -576,6 +576,8 @@ func TestConfigParse(t *testing.T) {
 		So(err, ShouldBeNil)
 		master := m.(*nfdMaster)
 		overrides := `{"noPublish": true, "enableTaints": true, "extraLabelNs": ["added.ns.io","added.kubernetes.io"], "denyLabelNs": ["denied.ns.io","denied.kubernetes.io"], "resourceLabels": ["vendor-1.com/feature-1","vendor-2.io/feature-2"], "labelWhiteList": "foo"}`
+		// Set fake (and invalid) apiserver address so that configuration doesn't fail in parsing the kubeconfig
+		os.Setenv("KUBERNETES_MASTER", ".")
 
 		Convey("and no core cmdline flags have been specified", func() {
 			So(master.configure("non-existing-file", overrides), ShouldBeNil)

pkg/nfd-master/nfd-master.go

@@ -749,10 +749,6 @@ func (m *nfdMaster) nfdAPIUpdateOneNode(node *corev1.Node) error {
 		return objs[i].Namespace < objs[j].Namespace
 	})
 
-	if m.config.NoPublish {
-		return nil
-	}
-
 	klog.V(1).InfoS("processing of node initiated by NodeFeature API", "nodeName", node.Name)
 
 	features := nfdv1alpha1.NewNodeFeatureSpec()
@@ -854,6 +850,11 @@ func (m *nfdMaster) refreshNodeFeatures(node *corev1.Node, labels map[string]str
 		taints = filterTaints(crTaints)
 	}
 
+	if m.config.NoPublish {
+		klog.V(1).InfoS("node update skipped, NoPublish=true", "nodeName", node.Name)
+		return nil
+	}
+
 	err := m.updateNodeObject(node, labels, annotations, extendedResources, taints)
 	if err != nil {
 		klog.ErrorS(err, "failed to update node", "nodeName", node.Name)
@@ -1229,17 +1230,15 @@ func (m *nfdMaster) configure(filepath string, overrides string) error {
 		return err
 	}
 
-	if !c.NoPublish {
-		kubeconfig, err := utils.GetKubeconfig(m.args.Kubeconfig)
-		if err != nil {
-			return err
-		}
-		cli, err := k8sclient.NewForConfig(kubeconfig)
-		if err != nil {
-			return err
-		}
-		m.k8sClient = cli
+	kubeconfig, err := utils.GetKubeconfig(m.args.Kubeconfig)
+	if err != nil {
+		return err
+	}
+	cli, err := k8sclient.NewForConfig(kubeconfig)
+	if err != nil {
+		return err
 	}
+	m.k8sClient = cli
 
 	// Pre-process DenyLabelNS into 2 lists: one for normal ns, and the other for wildcard ns
 	normalDeniedNs, wildcardDeniedNs := preProcessDeniedNamespaces(c.DenyLabelNs)

pkg/nfd-worker/nfd-worker_test.go

@@ -61,6 +61,8 @@ func setupTest(args *master.Args) testContext {
 
 	// Run nfd-master instance, intended to be used as the server counterpart
 	go func() {
+		// Set fake (and invalid) apiserver address so that nfd-master configuration doesn't fail in parsing the kubeconfig
+		os.Setenv("KUBERNETES_MASTER", ".")
 		ctx.errs <- ctx.master.Run()
 		close(ctx.errs)
 	}()