Finalize namespace

Finalize namespace when it is stuck in 'Terminating' after migration.
As controller-runtime client has yet support subresources like,
using client-go to invoke the Finalize API of Namespace.

pkg/apply/apply.go

@@ -7,11 +7,15 @@ import (
 
 	"github.com/pkg/errors"
 
+	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/equality"
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	uns "k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/types"
 	k8sclient "sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/client/config"
+	"k8s.io/client-go/kubernetes"
+	kscheme "k8s.io/client-go/kubernetes/scheme"
 )
 
 // ApplyObject applies the desired object against the apiserver,
@@ -49,6 +53,30 @@ func ApplyObject(ctx context.Context, client k8sclient.Client, obj *uns.Unstruct
 		return errors.Wrapf(err, "could not retrieve existing %s", objDesc)
 	}
 
+	if obj.GetKind() == "Namespace" {
+		ns := &v1.Namespace{}
+		if err := kscheme.Scheme.Convert(existing, ns, nil); err != nil {
+			return errors.Wrapf(err, "could not convert namespace %s", objDesc)
+		}
+		if ns.Status.Phase == v1.NamespaceTerminating {
+			log.Printf("finalize Namespace %s", objDesc)
+			ns.Spec.Finalizers = []v1.FinalizerName{}
+			// Get a config to for client-go
+			cfg, err := config.GetConfig()
+			if err != nil {
+				return errors.Wrapf(err, "could not create rest config")
+			}
+			clientset, err := kubernetes.NewForConfig(cfg)
+			if err != nil {
+				return errors.Wrapf(err, "could not create clientset")
+			}
+			if _, err := clientset.CoreV1().Namespaces().Finalize(ns); err != nil {
+				return errors.Wrapf(err, "could not finalize namespace %s", objDesc)
+			}
+			return nil
+		}
+	}
+
 	// Merge the desired object with what actually exists
 	if err := MergeObjectForUpdate(existing, obj); err != nil {
 		return errors.Wrapf(err, "could not merge object %s with existing", objDesc)