Add --watch flag to stream unready pod changes

Adds a -w/--watch flag that keeps running after the initial list,
streaming Added/Modified pod events and printing rows without headers
for a continuous view of unready pods.

cmd/cmd.go

@@ -11,6 +11,7 @@ import (
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/util/duration"
+	kwatch "k8s.io/apimachinery/pkg/watch"
 	"k8s.io/cli-runtime/pkg/genericclioptions"
 	"k8s.io/cli-runtime/pkg/printers"
 	"k8s.io/client-go/kubernetes"
@@ -19,6 +20,7 @@ import (
 func NewUnreadyCmd(ctx context.Context) *cobra.Command {
 	var kubernetesConfigFlags *genericclioptions.ConfigFlags
 	var allNamespacesFlag bool
+	var watchFlag bool
 
 	cmd := &cobra.Command{
 		Use:          "unready",
@@ -27,7 +29,7 @@ func NewUnreadyCmd(ctx context.Context) *cobra.Command {
 			if kubernetesConfigFlags.Namespace == nil || *kubernetesConfigFlags.Namespace == "" {
 				kubernetesConfigFlags.Namespace = new("default")
 			}
-			return run(ctx, kubernetesConfigFlags, allNamespacesFlag)
+			return run(ctx, kubernetesConfigFlags, allNamespacesFlag, watchFlag)
 		},
 	}
 
@@ -35,13 +37,14 @@ func NewUnreadyCmd(ctx context.Context) *cobra.Command {
 	kubernetesConfigFlags.AddFlags(cmd.Flags())
 
 	cmd.Flags().BoolVarP(&allNamespacesFlag, "all-namespaces", "A", false, "If present, list unready pods across all namespaces.")
+	cmd.Flags().BoolVarP(&watchFlag, "watch", "w", false, "Watch for changes to unready pods.")
 
 	cmd.AddCommand(version.NewVersionCmd(ctx))
 
 	return cmd
 }
 
-func run(ctx context.Context, configFlags *genericclioptions.ConfigFlags, allNamespaces bool) error {
+func run(ctx context.Context, configFlags *genericclioptions.ConfigFlags, allNamespaces bool, doWatch bool) error {
 	config, err := configFlags.ToRESTConfig()
 	if err != nil {
 		return fmt.Errorf("failed to read kubeconfig: %w", err)
@@ -63,17 +66,52 @@ func run(ctx context.Context, configFlags *genericclioptions.ConfigFlags, allNam
 	}
 
 	filtered := make([]corev1.Pod, 0)
-
 	for _, pod := range pods.Items {
 		if isNotReady(pod) {
 			filtered = append(filtered, pod)
 		}
 	}
 
-	return print(filtered)
+	if err := printPods(filtered, false); err != nil {
+		return err
+	}
+
+	if !doWatch {
+		return nil
+	}
+
+	watcher, err := clientset.CoreV1().Pods(namespace).Watch(ctx, metav1.ListOptions{
+		ResourceVersion: pods.ResourceVersion,
+	})
+	if err != nil {
+		return fmt.Errorf("failed watching Pods: %w", err)
+	}
+	defer watcher.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return nil
+		case event, ok := <-watcher.ResultChan():
+			if !ok {
+				return nil
+			}
+			pod, ok := event.Object.(*corev1.Pod)
+			if !ok {
+				continue
+			}
+			if event.Type == kwatch.Added || event.Type == kwatch.Modified {
+				if isNotReady(*pod) {
+					if err := printPods([]corev1.Pod{*pod}, true); err != nil {
+						return err
+					}
+				}
+			}
+		}
+	}
 }
 
-func print(pods []corev1.Pod) error {
+func printPods(pods []corev1.Pod, noHeaders bool) error {
 	table := metav1.Table{
 		ColumnDefinitions: []metav1.TableColumnDefinition{
 			{Name: "Namespace"},
@@ -95,7 +133,7 @@ func print(pods []corev1.Pod) error {
 		})
 	}
 
-	printer := printers.NewTablePrinter(printers.PrintOptions{})
+	printer := printers.NewTablePrinter(printers.PrintOptions{NoHeaders: noHeaders})
 	return printer.PrintObj(&table, os.Stdout)
 }