kubeadm: fix upgrade to be able to rollback ControlPlaneLocalMode

Author: chrischdi

cmd/kubeadm/app/cmd/phases/upgrade/apply/kubeconfig.go

@@ -24,7 +24,6 @@ import (
 
 	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/options"
 	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow"
-	"k8s.io/kubernetes/cmd/kubeadm/app/features"
 	"k8s.io/kubernetes/cmd/kubeadm/app/phases/upgrade"
 )
 
@@ -53,13 +52,11 @@ func runKubeconfig() func(c workflow.RunData) error {
 
 		cfg := data.InitCfg()
 
-		if features.Enabled(cfg.FeatureGates, features.ControlPlaneKubeletLocalMode) {
-			if err := upgrade.UpdateKubeletLocalMode(cfg, data.DryRun()); err != nil {
-				return errors.Wrap(err, "failed to update kubelet local mode")
-			}
+		if err := upgrade.UpdateKubeletKubeconfigServer(cfg, data.DryRun()); err != nil {
+			return errors.Wrap(err, "failed to update kubelet local mode")
 		}
 
-		fmt.Println("[upgrad/kubeconfig] The kubeconfig files for this node were successfully upgraded!")
+		fmt.Println("[upgrade/kubeconfig] The kubeconfig files for this node were successfully upgraded!")
 
 		return nil
 	}

cmd/kubeadm/app/cmd/phases/upgrade/node/kubeconfig.go

@@ -24,7 +24,6 @@ import (
 
 	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/options"
 	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow"
-	"k8s.io/kubernetes/cmd/kubeadm/app/features"
 	"k8s.io/kubernetes/cmd/kubeadm/app/phases/upgrade"
 )
 
@@ -60,10 +59,8 @@ func runKubeconfig() func(c workflow.RunData) error {
 		// Otherwise, retrieve all the info required for kubeconfig upgrade.
 		cfg := data.InitCfg()
 
-		if features.Enabled(cfg.FeatureGates, features.ControlPlaneKubeletLocalMode) {
-			if err := upgrade.UpdateKubeletLocalMode(cfg, data.DryRun()); err != nil {
-				return errors.Wrap(err, "failed to update kubelet local mode")
-			}
+		if err := upgrade.UpdateKubeletKubeconfigServer(cfg, data.DryRun()); err != nil {
+			return errors.Wrap(err, "failed to update kubelet local mode")
 		}
 
 		fmt.Println("[upgrade/kubeconfig] The kubeconfig files for this node were successfully upgraded!")

cmd/kubeadm/app/phases/upgrade/postupgrade.go

@@ -193,11 +193,11 @@ func WriteKubeletConfigFiles(cfg *kubeadmapi.InitConfiguration, kubeletConfigDir
 	return nil
 }
 
-// UpdateKubeletLocalMode changes the Server URL in the kubelets kubeconfig to the local API endpoint if it is currently
-// set to the ControlPlaneEndpoint.
-// TODO: remove this function once kubeletKubeConfigFilePath goes GA and is hardcoded to enabled by default:
+// UpdateKubeletKubeconfigServer changes the Server URL in the kubelets kubeconfig if necessary depending on the
+// ControlPlaneKubeletLocalMode feature gate.
+// TODO: remove this function once ControlPlaneKubeletLocalMode goes GA and is hardcoded to be enabled by default:
 // https://github.com/kubernetes/kubeadm/issues/2271
-func UpdateKubeletLocalMode(cfg *kubeadmapi.InitConfiguration, dryRun bool) error {
+func UpdateKubeletKubeconfigServer(cfg *kubeadmapi.InitConfiguration, dryRun bool) error {
 	kubeletKubeConfigFilePath := filepath.Join(kubeadmconstants.KubernetesDir, kubeadmconstants.KubeletKubeConfigFileName)
 
 	if _, err := os.Stat(kubeletKubeConfigFilePath); err != nil {
@@ -228,19 +228,30 @@ func UpdateKubeletLocalMode(cfg *kubeadmapi.InitConfiguration, dryRun bool) erro
 		return err
 	}
 
-	// Skip changing kubeconfig file if Server does not match the ControlPlaneEndpoint.
-	if config.Clusters[configContext.Cluster].Server != controlPlaneAPIEndpoint || controlPlaneAPIEndpoint == localAPIEndpoint {
-		klog.V(2).Infof("Skipping update of the Server URL in %s, because it's already not equal to %q or already matches the localAPIEndpoint", kubeletKubeConfigFilePath, cfg.ControlPlaneEndpoint)
-		return nil
+	var targetServer string
+	if features.Enabled(cfg.FeatureGates, features.ControlPlaneKubeletLocalMode) {
+		// Skip changing kubeconfig file if Server does not match the ControlPlaneEndpoint.
+		if config.Clusters[configContext.Cluster].Server != controlPlaneAPIEndpoint || controlPlaneAPIEndpoint == localAPIEndpoint {
+			klog.V(2).Infof("Skipping update of the Server URL in %s, because it's already not equal to %q or already matches the localAPIEndpoint", kubeletKubeConfigFilePath, controlPlaneAPIEndpoint)
+			return nil
+		}
+		targetServer = localAPIEndpoint
+	} else {
+		// Skip changing kubeconfig file if Server does not match the localAPIEndpoint.
+		if config.Clusters[configContext.Cluster].Server != localAPIEndpoint {
+			klog.V(2).Infof("Skipping update of the Server URL in %s, because it already matches the controlPlaneAPIEndpoint", kubeletKubeConfigFilePath)
+			return nil
+		}
+		targetServer = controlPlaneAPIEndpoint
 	}
 
 	if dryRun {
-		fmt.Printf("[dryrun] Would change the Server URL from %q to %q in %s and try to restart kubelet\n", config.Clusters[configContext.Cluster].Server, localAPIEndpoint, kubeletKubeConfigFilePath)
+		fmt.Printf("[dryrun] Would change the Server URL from %q to %q in %s and try to restart kubelet\n", config.Clusters[configContext.Cluster].Server, targetServer, kubeletKubeConfigFilePath)
 		return nil
 	}
 
-	klog.V(1).Infof("Changing the Server URL from %q to %q in %s", config.Clusters[configContext.Cluster].Server, localAPIEndpoint, kubeletKubeConfigFilePath)
-	config.Clusters[configContext.Cluster].Server = localAPIEndpoint
+	klog.V(1).Infof("Changing the Server URL from %q to %q in %s", config.Clusters[configContext.Cluster].Server, targetServer, kubeletKubeConfigFilePath)
+	config.Clusters[configContext.Cluster].Server = targetServer
 
 	if err := clientcmd.WriteToFile(*config, kubeletKubeConfigFilePath); err != nil {
 		return err