kubectl/drain: add disable-eviction option

Currently, if eviction is supported during a drain operation,
eviction is always used.

This commit allows the user to specify disabling eviction.
This is particularly useful when you wish to ignore
PodDisruptionBudgets after a normal drain has failed for
some time.

Author: michaelgugino

staging/src/k8s.io/kubectl/pkg/cmd/drain/drain.go

@@ -192,6 +192,7 @@ func NewCmdDrain(f cmdutil.Factory, ioStreams genericclioptions.IOStreams) *cobr
 	cmd.Flags().DurationVar(&o.drainer.Timeout, "timeout", o.drainer.Timeout, "The length of time to wait before giving up, zero means infinite")
 	cmd.Flags().StringVarP(&o.drainer.Selector, "selector", "l", o.drainer.Selector, "Selector (label query) to filter on")
 	cmd.Flags().StringVarP(&o.drainer.PodSelector, "pod-selector", "", o.drainer.PodSelector, "Label selector to filter pods on the node")
+	cmd.Flags().BoolVar(&o.drainer.DisableEviction, "disable-eviction", o.drainer.DisableEviction, "Force drain to use delete, even if eviction is supported. This will bypass checking PodDisruptionBudgets, use with caution.")
 
 	cmdutil.AddDryRunFlag(cmd)
 	return cmd

staging/src/k8s.io/kubectl/pkg/drain/drain.go

@@ -51,8 +51,12 @@ type Helper struct {
 	DeleteLocalData     bool
 	Selector            string
 	PodSelector         string
-	Out                 io.Writer
-	ErrOut              io.Writer
+
+	// DisableEviction forces drain to use delete rather than evict
+	DisableEviction bool
+
+	Out    io.Writer
+	ErrOut io.Writer
 
 	// TODO(justinsb): unnecessary?
 	DryRun bool
@@ -178,17 +182,20 @@ func (d *Helper) DeleteOrEvictPods(pods []corev1.Pod) error {
 		return nil
 	}
 
-	policyGroupVersion, err := CheckEvictionSupport(d.Client)
-	if err != nil {
-		return err
-	}
-
 	// TODO(justinsb): unnecessary?
 	getPodFn := func(namespace, name string) (*corev1.Pod, error) {
 		return d.Client.CoreV1().Pods(namespace).Get(name, metav1.GetOptions{})
 	}
-	if len(policyGroupVersion) > 0 {
-		return d.evictPods(pods, policyGroupVersion, getPodFn)
+
+	if !d.DisableEviction {
+		policyGroupVersion, err := CheckEvictionSupport(d.Client)
+		if err != nil {
+			return err
+		}
+
+		if len(policyGroupVersion) > 0 {
+			return d.evictPods(pods, policyGroupVersion, getPodFn)
+		}
 	}
 
 	return d.deletePods(pods, getPodFn)

staging/src/k8s.io/kubectl/pkg/drain/drain_test.go

@@ -220,90 +220,114 @@ func TestCheckEvictionSupport(t *testing.T) {
 }
 
 func TestDeleteOrEvict(t *testing.T) {
-	for _, evictionSupported := range []bool{true, false} {
-		evictionSupported := evictionSupported
-		t.Run(fmt.Sprintf("evictionSupported=%v", evictionSupported),
-			func(t *testing.T) {
-				h := &Helper{
-					Out:                os.Stdout,
-					GracePeriodSeconds: 10,
-				}
-
-				// Create 4 pods, and try to remove the first 2
-				var expectedEvictions []policyv1beta1.Eviction
-				var create []runtime.Object
-				deletePods := []corev1.Pod{}
-				for i := 1; i <= 4; i++ {
-					pod := &corev1.Pod{}
-					pod.Name = fmt.Sprintf("mypod-%d", i)
-					pod.Namespace = "default"
+	tests := []struct {
+		description       string
+		evictionSupported bool
+		disableEviction   bool
+	}{
+		{
+			description:       "eviction supported/enabled",
+			evictionSupported: true,
+			disableEviction:   false,
+		},
+		{
+			description:       "eviction unsupported/disabled",
+			evictionSupported: false,
+			disableEviction:   false,
+		},
+		{
+			description:       "eviction supported/disabled",
+			evictionSupported: true,
+			disableEviction:   true,
+		},
+		{
+			description:       "eviction unsupported/disabled",
+			evictionSupported: false,
+			disableEviction:   false,
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.description, func(t *testing.T) {
+			h := &Helper{
+				Out:                os.Stdout,
+				GracePeriodSeconds: 10,
+			}
 
-					create = append(create, pod)
-					if i <= 2 {
-						deletePods = append(deletePods, *pod)
+			// Create 4 pods, and try to remove the first 2
+			var expectedEvictions []policyv1beta1.Eviction
+			var create []runtime.Object
+			deletePods := []corev1.Pod{}
+			for i := 1; i <= 4; i++ {
+				pod := &corev1.Pod{}
+				pod.Name = fmt.Sprintf("mypod-%d", i)
+				pod.Namespace = "default"
 
-						if evictionSupported {
-							eviction := policyv1beta1.Eviction{}
-							eviction.Kind = "Eviction"
-							eviction.APIVersion = "policy/v1"
-							eviction.Namespace = pod.Namespace
-							eviction.Name = pod.Name
+				create = append(create, pod)
+				if i <= 2 {
+					deletePods = append(deletePods, *pod)
 
-							gracePeriodSeconds := int64(h.GracePeriodSeconds)
-							eviction.DeleteOptions = &metav1.DeleteOptions{
-								GracePeriodSeconds: &gracePeriodSeconds,
-							}
+					if tc.evictionSupported && !tc.disableEviction {
+						eviction := policyv1beta1.Eviction{}
+						eviction.Kind = "Eviction"
+						eviction.APIVersion = "policy/v1"
+						eviction.Namespace = pod.Namespace
+						eviction.Name = pod.Name
 
-							expectedEvictions = append(expectedEvictions, eviction)
+						gracePeriodSeconds := int64(h.GracePeriodSeconds)
+						eviction.DeleteOptions = &metav1.DeleteOptions{
+							GracePeriodSeconds: &gracePeriodSeconds,
 						}
+
+						expectedEvictions = append(expectedEvictions, eviction)
 					}
 				}
+			}
 
-				// Build the fake client
-				k := fake.NewSimpleClientset(create...)
-				if evictionSupported {
-					addEvictionSupport(t, k)
-				}
-				h.Client = k
+			// Build the fake client
+			k := fake.NewSimpleClientset(create...)
+			if tc.evictionSupported {
+				addEvictionSupport(t, k)
+			}
+			h.Client = k
+			h.DisableEviction = tc.disableEviction
+			// Do the eviction
+			if err := h.DeleteOrEvictPods(deletePods); err != nil {
+				t.Fatalf("error from DeleteOrEvictPods: %v", err)
+			}
 
-				// Do the eviction
-				if err := h.DeleteOrEvictPods(deletePods); err != nil {
-					t.Fatalf("error from DeleteOrEvictPods: %v", err)
+			// Test that other pods are still there
+			var remainingPods []string
+			{
+				podList, err := k.CoreV1().Pods("").List(metav1.ListOptions{})
+				if err != nil {
+					t.Fatalf("error listing pods: %v", err)
 				}
 
-				// Test that other pods are still there
-				var remainingPods []string
-				{
-					podList, err := k.CoreV1().Pods("").List(metav1.ListOptions{})
-					if err != nil {
-						t.Fatalf("error listing pods: %v", err)
-					}
-
-					for _, pod := range podList.Items {
-						remainingPods = append(remainingPods, pod.Namespace+"/"+pod.Name)
-					}
-					sort.Strings(remainingPods)
-				}
-				expected := []string{"default/mypod-3", "default/mypod-4"}
-				if !reflect.DeepEqual(remainingPods, expected) {
-					t.Errorf("unexpected remaining pods after DeleteOrEvictPods; actual %v; expected %v", remainingPods, expected)
+				for _, pod := range podList.Items {
+					remainingPods = append(remainingPods, pod.Namespace+"/"+pod.Name)
 				}
+				sort.Strings(remainingPods)
+			}
+			expected := []string{"default/mypod-3", "default/mypod-4"}
+			if !reflect.DeepEqual(remainingPods, expected) {
+				t.Errorf("%s: unexpected remaining pods after DeleteOrEvictPods; actual %v; expected %v", tc.description, remainingPods, expected)
+			}
 
-				// Test that pods were evicted as expected
-				var actualEvictions []policyv1beta1.Eviction
-				for _, action := range k.Actions() {
-					if action.GetVerb() != "create" || action.GetResource().Resource != "pods" || action.GetSubresource() != "eviction" {
-						continue
-					}
-					eviction := *action.(ktest.CreateAction).GetObject().(*policyv1beta1.Eviction)
-					actualEvictions = append(actualEvictions, eviction)
-				}
-				sort.Slice(actualEvictions, func(i, j int) bool {
-					return actualEvictions[i].Name < actualEvictions[j].Name
-				})
-				if !reflect.DeepEqual(actualEvictions, expectedEvictions) {
-					t.Errorf("unexpected evictions; actual %v; expected %v", actualEvictions, expectedEvictions)
+			// Test that pods were evicted as expected
+			var actualEvictions []policyv1beta1.Eviction
+			for _, action := range k.Actions() {
+				if action.GetVerb() != "create" || action.GetResource().Resource != "pods" || action.GetSubresource() != "eviction" {
+					continue
 				}
+				eviction := *action.(ktest.CreateAction).GetObject().(*policyv1beta1.Eviction)
+				actualEvictions = append(actualEvictions, eviction)
+			}
+			sort.Slice(actualEvictions, func(i, j int) bool {
+				return actualEvictions[i].Name < actualEvictions[j].Name
 			})
+			if !reflect.DeepEqual(actualEvictions, expectedEvictions) {
+				t.Errorf("%s: unexpected evictions; actual %v; expected %v", tc.description, actualEvictions, expectedEvictions)
+			}
+		})
 	}
 }