Add new subcommand for the kubectl-hns plugin

Add a subcommand to list resources by their parent namespace:

  kubectl hns get -n <parent ns> <resource>

Author: cmurphy

internal/kubectl/get.go

@@ -0,0 +1,109 @@
+package kubectl
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/cli-runtime/pkg/printers"
+	"k8s.io/client-go/dynamic"
+	"k8s.io/client-go/kubernetes/scheme"
+
+	api "sigs.k8s.io/hierarchical-namespaces/api/v1alpha2"
+)
+
+var (
+	watch         bool
+	parent        string
+	allNamespaces bool
+)
+
+var getCmd = &cobra.Command{
+	Use:   "get",
+	Short: "list resources",
+	RunE: func(c *cobra.Command, args []string) error {
+		if len(args) == 0 {
+			return fmt.Errorf("not enough arguments to 'get'")
+		}
+		if len(args) > 1 {
+			return fmt.Errorf("too many arguments to 'get'")
+		}
+		d := newDoer(args[0])
+		rv, err := d.get(args[0])
+		if err != nil {
+			return err
+		}
+		if watch {
+			return d.watch(args[0], rv)
+		}
+		return nil
+	},
+}
+
+func newGetCmd() *cobra.Command {
+	return getCmd
+}
+
+func init() {
+	getCmd.Flags().BoolVarP(&watch, "watch", "w", false, "watch for changes")
+	getCmd.PersistentFlags().StringVarP(&parent, "namespace", "n", "default", "parent namespace to scope request to")
+	getCmd.PersistentFlags().BoolVarP(&allNamespaces, "all-namespaces", "A", false, "list across all namespaces (equivalent to kubectl get <resource> -A)")
+}
+
+type doer struct {
+	client  dynamic.ResourceInterface
+	printer printers.ResourcePrinter
+}
+
+func newDoer(resource string) doer {
+	client := getClient(resource)
+	// See https://iximiuz.com/en/posts/kubernetes-api-go-cli/#pretty-print-kubernetes-object-as-yamljsontables for information on k8s printers
+	printOpts := printers.PrintOptions{WithNamespace: true}
+	return doer{
+		client:  client,
+		printer: printers.NewTypeSetter(scheme.Scheme).ToPrinter(printers.NewTablePrinter(printOpts)),
+	}
+}
+
+func getClient(resource string) dynamic.ResourceInterface {
+	gvr := api.ResourcesGroupVersion.WithResource(resource)
+	gvr, _ = mapper.ResourceFor(gvr)
+	resourceClient := dynamicClient.Resource(gvr)
+	if allNamespaces {
+		return resourceClient
+	}
+	return resourceClient.Namespace(parent)
+}
+
+func (d doer) get(resource string) (string, error) {
+	unst, err := d.client.List(context.TODO(), metav1.ListOptions{})
+	if err != nil {
+		return "", err
+	}
+	rv := unst.GetResourceVersion()
+	if err = d.printer.PrintObj(unst, os.Stdout); err != nil {
+		return rv, err
+	}
+	return rv, nil
+}
+
+func (d doer) watch(resource, rv string) error {
+	if rv == "" {
+		rv = "0"
+	}
+	opts := metav1.ListOptions{
+		ResourceVersion: rv,
+	}
+	watcher, err := d.client.Watch(context.TODO(), opts)
+	if err != nil {
+		return err
+	}
+	for event := range watcher.ResultChan() {
+		if err = d.printer.PrintObj(event.Object, os.Stdout); err != nil {
+			return err
+		}
+	}
+	return nil
+}

internal/kubectl/root.go

@@ -24,10 +24,12 @@ import (
 
 	"github.com/spf13/cobra"
 	"k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apimachinery/pkg/api/meta"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime/serializer"
 	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	"k8s.io/cli-runtime/pkg/genericclioptions"
+	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/kubernetes/scheme"
 	_ "k8s.io/client-go/plugin/pkg/client/auth"
@@ -41,6 +43,8 @@ var k8sClient *kubernetes.Clientset
 var hncClient *rest.RESTClient
 var rootCmd *cobra.Command
 var client Client
+var dynamicClient dynamic.Interface
+var mapper meta.RESTMapper
 
 type realClient struct{}
 type anchorStatus map[string]string
@@ -98,6 +102,16 @@ func init() {
 				return err
 			}
 
+			mapper, err = kubecfgFlags.ToRESTMapper()
+			if err != nil {
+				return err
+			}
+
+			dynamicClient, err = dynamic.NewForConfig(config)
+			if err != nil {
+				return err
+			}
+
 			return nil
 		},
 	}
@@ -111,6 +125,7 @@ func init() {
 	rootCmd.AddCommand(newConfigCmd())
 	rootCmd.AddCommand(newVersionCmd())
 	rootCmd.AddCommand(newHrqCmd())
+	rootCmd.AddCommand(newGetCmd())
 }
 
 func Execute() {