Fix pod deletion to be compatible with Kubernetes 1.9

* Check each pod's OwnerReferences to determine whether it is
owned by an existing Daemonset. If so, exclude it from deletion
as the pod would just be recreated by the Daemonset controller
* Drop usage of CreatedByAnnotation to deserialize the owner
object of a pod when listing pods to delete during agent drains

Author: dghubble

pkg/drain/drain.go

@@ -7,9 +7,7 @@ import (
 	"k8s.io/apimachinery/pkg/api/errors"
 	v1meta "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/fields"
-	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/client-go/kubernetes"
-	"k8s.io/client-go/kubernetes/scheme"
 	kubelettypes "k8s.io/kubernetes/pkg/kubelet/types"
 )
 
@@ -26,36 +24,19 @@ func GetPodsForDeletion(kc kubernetes.Interface, node string) (pods []v1.Pod, er
 		return pods, err
 	}
 
+	// Delete pods, even if they are lone pods without a controller. As an
+	// exception, skip mirror pods and daemonset pods with an existing
+	// daemonset (since the daemonset owner would recreate them anyway).
 	for _, pod := range podList.Items {
+
 		// skip mirror pods
 		if _, ok := pod.Annotations[kubelettypes.ConfigMirrorAnnotationKey]; ok {
 			continue
 		}
 
-		// unlike kubelet we don't care if you have emptyDir volumes or
-		// are not replicated via some controller. sorry.
-
-		// but we do skip daemonset pods, since ds controller will just restart them anyways.
-		// As an exception, we do delete daemonset pods that have been "orphaned" by their controller.
-		if creatorRef, ok := pod.Annotations[v1.CreatedByAnnotation]; ok {
-			// decode ref to find kind
-			sr := &v1.SerializedReference{}
-			if err := runtime.DecodeInto(scheme.Codecs.UniversalDecoder(), []byte(creatorRef), sr); err != nil {
-				// really shouldn't happen but at least complain verbosely if it does
-				return nil, fmt.Errorf("failed decoding %q annotation on pod %q: %v", v1.CreatedByAnnotation, pod.Name, err)
-			}
-
-			if sr.Reference.Kind == "DaemonSet" {
-				_, err := getDaemonsetController(kc, sr)
-				if err == nil {
-					// it exists, skip it
-					continue
-				}
-				if !errors.IsNotFound(err) {
-					return nil, fmt.Errorf("failed to get controller of pod %q: %v", pod.Name, err)
-				}
-				// else the controller is gone, fall through to delete this orphan
-			}
+		// check if pod is a daemonset owner
+		if _, err = getOwnerDaemonset(kc, pod); err == nil {
+			continue
 		}
 
 		pods = append(pods, pod)
@@ -64,13 +45,33 @@ func GetPodsForDeletion(kc kubernetes.Interface, node string) (pods []v1.Pod, er
 	return pods, nil
 }
 
-// Pared down version of
-// https://github.com/kubernetes/kubernetes/blob/cbbf22a7d2b06a55066b16885a4baaf4ce92d3a4/pkg/kubectl/cmd/drain.go's
-// getDaemonsetController().
-func getDaemonsetController(kc kubernetes.Interface, sr *v1.SerializedReference) (interface{}, error) {
-	switch sr.Reference.Kind {
+// getOwnerDaemonset returns an existing DaemonSet owner if it exists.
+func getOwnerDaemonset(kc kubernetes.Interface, pod v1.Pod) (interface{}, error) {
+	if len(pod.OwnerReferences) == 0 {
+		return nil, fmt.Errorf("pod %q has no owner objects", pod.Name)
+	}
+	for _, ownerRef := range pod.OwnerReferences {
+		// skip pod if it is owned by an existing daemonset
+		if ownerRef.Kind == "DaemonSet" {
+			ds, err := getDaemonsetController(kc, pod.Namespace, &ownerRef)
+			if err == nil {
+				// daemonset owner exists
+				return ds, nil
+			}
+			if !errors.IsNotFound(err) {
+				return nil, fmt.Errorf("failed to get controller of pod %q: %v", pod.Name, err)
+			}
+		}
+	}
+	// pod may have owners, but they don't exist or aren't daemonsets
+	return nil, fmt.Errorf("pod %q has no existing damonset owner", pod.Name)
+}
+
+// Stripped down version of https://github.com/kubernetes/kubernetes/blob/1bc56825a2dff06f29663a024ee339c25e6e6280/pkg/kubectl/cmd/drain.go#L272
+func getDaemonsetController(kc kubernetes.Interface, namespace string, controllerRef *v1meta.OwnerReference) (interface{}, error) {
+	switch controllerRef.Kind {
 	case "DaemonSet":
-		return kc.ExtensionsV1beta1().DaemonSets(sr.Reference.Namespace).Get(sr.Reference.Name, v1meta.GetOptions{})
+		return kc.ExtensionsV1beta1().DaemonSets(namespace).Get(controllerRef.Name, v1meta.GetOptions{})
 	}
-	return nil, fmt.Errorf("unknown controller kind %q", sr.Reference.Kind)
+	return nil, fmt.Errorf("Unknown controller kind %q", controllerRef.Kind)
 }