kubectl: run validation for 'top pod'

pkg/kubectl/cmd/top_node.go

@@ -119,6 +119,9 @@ func (o TopNodeOptions) RunTopNode() error {
 	if err != nil {
 		return err
 	}
+	if len(metrics) == 0 {
+		return errors.New("metrics not available yet")
+	}
 
 	var nodes []api.Node
 	if len(o.ResourceName) > 0 {

pkg/kubectl/cmd/top_pod.go

@@ -79,6 +79,9 @@ func NewCmdTopPod(f *cmdutil.Factory, out io.Writer) *cobra.Command {
 			if err := options.Complete(f, cmd, args, out); err != nil {
 				cmdutil.CheckErr(err)
 			}
+			if err := options.Validate(); err != nil {
+				cmdutil.CheckErr(cmdutil.UsageError(cmd, err.Error()))
+			}
 			if err := options.RunTopPod(); err != nil {
 				cmdutil.CheckErr(err)
 			}