skip eviction when replica count is below evictor minReplicas threshold setting

Signed-off-by: Amir Alavi <amiralavi7@gmail.com>

README.md

@@ -142,6 +142,7 @@ The Default Evictor Plugin is used by default for filtering pods before processi
 |`labelSelector`|`metav1.LabelSelector`||(see [label filtering](#label-filtering))|
 |`priorityThreshold`|`priorityThreshold`||(see [priority filtering](#priority-filtering))|
 |`nodeFit`|`bool`|`false`|(see [node fit filtering](#node-fit-filtering))|
+|`minReplicas`|`uint`|`0`| ignore eviction of pods where owner (e.g. `ReplicaSet`) replicas is below this threshold |
 
 ### Example policy
 
@@ -166,6 +167,7 @@ profiles:
         evictFailedBarePods: true
         evictLocalStoragePods: true
         nodeFit: true
+        minReplicas: 2
     plugins:
       # DefaultEvictor is enabled for both `filter` and `preEvictionFilter`
       # filter:

pkg/descheduler/pod/pods.go

@@ -142,21 +142,25 @@ func BuildGetPodsAssignedToNodeFunc(podInformer cache.SharedIndexInformer) (GetP
 		if err != nil {
 			return nil, err
 		}
-		pods := make([]*v1.Pod, 0, len(objs))
-		for _, obj := range objs {
-			pod, ok := obj.(*v1.Pod)
-			if !ok {
-				continue
-			}
-			if filter(pod) {
-				pods = append(pods, pod)
-			}
-		}
-		return pods, nil
+		return ConvertToPods(objs, filter), nil
 	}
 	return getPodsAssignedToNode, nil
 }
 
+func ConvertToPods(objs []interface{}, filter FilterFunc) []*v1.Pod {
+	pods := make([]*v1.Pod, 0, len(objs))
+	for _, obj := range objs {
+		pod, ok := obj.(*v1.Pod)
+		if !ok {
+			continue
+		}
+		if filter == nil || filter(pod) {
+			pods = append(pods, pod)
+		}
+	}
+	return pods
+}
+
 // ListPodsOnNodes returns all pods on given nodes.
 func ListPodsOnNodes(nodes []*v1.Node, getPodsAssignedToNode GetPodsAssignedToNodeFunc, filter FilterFunc) ([]*v1.Pod, error) {
 	pods := make([]*v1.Pod, 0)
@@ -215,6 +219,14 @@ func OwnerRef(pod *v1.Pod) []metav1.OwnerReference {
 	return pod.ObjectMeta.GetOwnerReferences()
 }
 
+func OwnerRefUIDs(pod *v1.Pod) []string {
+	var ownerRefUIDs []string
+	for _, ownerRef := range OwnerRef(pod) {
+		ownerRefUIDs = append(ownerRefUIDs, string(ownerRef.UID))
+	}
+	return ownerRefUIDs
+}
+
 func IsBestEffortPod(pod *v1.Pod) bool {
 	return utils.GetPodQOS(pod) == v1.PodQOSBestEffort
 }

pkg/framework/plugins/defaultevictor/defaultevictor.go

@@ -16,13 +16,15 @@ package defaultevictor
 import (
 	// "context"
 	"context"
+	"errors"
 	"fmt"
 
 	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/runtime"
-	"k8s.io/apimachinery/pkg/util/errors"
+	utilerrors "k8s.io/apimachinery/pkg/util/errors"
+	"k8s.io/client-go/tools/cache"
 	"k8s.io/klog/v2"
 	nodeutil "sigs.k8s.io/descheduler/pkg/descheduler/node"
 	podutil "sigs.k8s.io/descheduler/pkg/descheduler/pod"
@@ -143,6 +145,36 @@ func New(args runtime.Object, handle frameworktypes.Handle) (frameworktypes.Plug
 		})
 	}
 
+	if defaultEvictorArgs.MinReplicas > 1 {
+		indexName := "metadata.ownerReferences"
+		indexer, err := getPodIndexerByOwnerRefs(indexName, handle)
+		if err != nil {
+			return nil, err
+		}
+		ev.constraints = append(ev.constraints, func(pod *v1.Pod) error {
+			if len(pod.OwnerReferences) == 0 {
+				return nil
+			}
+
+			if len(pod.OwnerReferences) > 1 {
+				klog.V(5).InfoS("pod has multiple owner references which is not supported for minReplicas check", "size", len(pod.OwnerReferences), "pod", klog.KObj(pod))
+				return nil
+			}
+
+			ownerRef := pod.OwnerReferences[0]
+			objs, err := indexer.ByIndex(indexName, string(ownerRef.UID))
+			if err != nil {
+				return fmt.Errorf("unable to list pods for minReplicas filter in the policy parameter")
+			}
+
+			if uint(len(objs)) < defaultEvictorArgs.MinReplicas {
+				return fmt.Errorf("owner has %d replicas which is less than minReplicas of %d", len(objs), defaultEvictorArgs.MinReplicas)
+			}
+
+			return nil
+		})
+	}
+
 	return ev, nil
 }
 
@@ -199,9 +231,28 @@ func (d *DefaultEvictor) Filter(pod *v1.Pod) bool {
 	}
 
 	if len(checkErrs) > 0 {
-		klog.V(4).InfoS("Pod fails the following checks", "pod", klog.KObj(pod), "checks", errors.NewAggregate(checkErrs).Error())
+		klog.V(4).InfoS("Pod fails the following checks", "pod", klog.KObj(pod), "checks", utilerrors.NewAggregate(checkErrs).Error())
 		return false
 	}
 
 	return true
 }
+
+func getPodIndexerByOwnerRefs(indexName string, handle frameworktypes.Handle) (cache.Indexer, error) {
+	podInformer := handle.SharedInformerFactory().Core().V1().Pods().Informer()
+	if err := podInformer.AddIndexers(cache.Indexers{
+		indexName: func(obj interface{}) ([]string, error) {
+			pod, ok := obj.(*v1.Pod)
+			if !ok {
+				return []string{}, errors.New("unexpected object")
+			}
+
+			return podutil.OwnerRefUIDs(pod), nil
+		},
+	}); err != nil {
+		return nil, err
+	}
+
+	indexer := podInformer.GetIndexer()
+	return indexer, nil
+}

pkg/framework/plugins/defaultevictor/defaultevictor_test.go

@@ -20,6 +20,7 @@ import (
 	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/util/uuid"
 	"k8s.io/client-go/informers"
 	"k8s.io/client-go/kubernetes/fake"
 	"sigs.k8s.io/descheduler/pkg/api"
@@ -363,6 +364,8 @@ func TestDefaultEvictorFilter(t *testing.T) {
 	nodeTaintKey := "hardware"
 	nodeTaintValue := "gpu"
 
+	ownerRefUUID := uuid.NewUUID()
+
 	type testCase struct {
 		description             string
 		pods                    []*v1.Pod
@@ -372,6 +375,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 		evictSystemCriticalPods bool
 		priorityThreshold       *int32
 		nodeFit                 bool
+		minReplicas             uint
 		result                  bool
 	}
 
@@ -527,7 +531,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			evictSystemCriticalPods: false,
 			result:                  true,
 		}, {
-			description: "Pod not evicted becasuse it is part of a daemonSet",
+			description: "Pod not evicted because it is part of a daemonSet",
 			pods: []*v1.Pod{
 				test.BuildTestPod("p8", 400, 0, n1.Name, func(pod *v1.Pod) {
 					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
@@ -538,7 +542,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			evictSystemCriticalPods: false,
 			result:                  false,
 		}, {
-			description: "Pod is evicted becasuse it is part of a daemonSet, but it has scheduler.alpha.kubernetes.io/evict annotation",
+			description: "Pod is evicted because it is part of a daemonSet, but it has scheduler.alpha.kubernetes.io/evict annotation",
 			pods: []*v1.Pod{
 				test.BuildTestPod("p9", 400, 0, n1.Name, func(pod *v1.Pod) {
 					pod.Annotations = map[string]string{"descheduler.alpha.kubernetes.io/evict": "true"}
@@ -549,7 +553,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			evictSystemCriticalPods: false,
 			result:                  true,
 		}, {
-			description: "Pod not evicted becasuse it is a mirror poddsa",
+			description: "Pod not evicted because it is a mirror poddsa",
 			pods: []*v1.Pod{
 				test.BuildTestPod("p10", 400, 0, n1.Name, func(pod *v1.Pod) {
 					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
@@ -560,7 +564,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			evictSystemCriticalPods: false,
 			result:                  false,
 		}, {
-			description: "Pod is evicted becasuse it is a mirror pod, but it has scheduler.alpha.kubernetes.io/evict annotation",
+			description: "Pod is evicted because it is a mirror pod, but it has scheduler.alpha.kubernetes.io/evict annotation",
 			pods: []*v1.Pod{
 				test.BuildTestPod("p11", 400, 0, n1.Name, func(pod *v1.Pod) {
 					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
@@ -572,7 +576,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			evictSystemCriticalPods: false,
 			result:                  true,
 		}, {
-			description: "Pod not evicted becasuse it has system critical priority",
+			description: "Pod not evicted because it has system critical priority",
 			pods: []*v1.Pod{
 				test.BuildTestPod("p12", 400, 0, n1.Name, func(pod *v1.Pod) {
 					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
@@ -584,7 +588,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			evictSystemCriticalPods: false,
 			result:                  false,
 		}, {
-			description: "Pod is evicted becasuse it has system critical priority, but it has scheduler.alpha.kubernetes.io/evict annotation",
+			description: "Pod is evicted because it has system critical priority, but it has scheduler.alpha.kubernetes.io/evict annotation",
 			pods: []*v1.Pod{
 				test.BuildTestPod("p13", 400, 0, n1.Name, func(pod *v1.Pod) {
 					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
@@ -599,7 +603,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			evictSystemCriticalPods: false,
 			result:                  true,
 		}, {
-			description: "Pod not evicted becasuse it has a priority higher than the configured priority threshold",
+			description: "Pod not evicted because it has a priority higher than the configured priority threshold",
 			pods: []*v1.Pod{
 				test.BuildTestPod("p14", 400, 0, n1.Name, func(pod *v1.Pod) {
 					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
@@ -611,7 +615,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			priorityThreshold:       &lowPriority,
 			result:                  false,
 		}, {
-			description: "Pod is evicted becasuse it has a priority higher than the configured priority threshold, but it has scheduler.alpha.kubernetes.io/evict annotation",
+			description: "Pod is evicted because it has a priority higher than the configured priority threshold, but it has scheduler.alpha.kubernetes.io/evict annotation",
 			pods: []*v1.Pod{
 				test.BuildTestPod("p15", 400, 0, n1.Name, func(pod *v1.Pod) {
 					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
@@ -624,7 +628,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			priorityThreshold:       &lowPriority,
 			result:                  true,
 		}, {
-			description: "Pod is evicted becasuse it has system critical priority, but evictSystemCriticalPods = true",
+			description: "Pod is evicted because it has system critical priority, but evictSystemCriticalPods = true",
 			pods: []*v1.Pod{
 				test.BuildTestPod("p16", 400, 0, n1.Name, func(pod *v1.Pod) {
 					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
@@ -636,7 +640,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			evictSystemCriticalPods: true,
 			result:                  true,
 		}, {
-			description: "Pod is evicted becasuse it has system critical priority, but evictSystemCriticalPods = true and it has scheduler.alpha.kubernetes.io/evict annotation",
+			description: "Pod is evicted because it has system critical priority, but evictSystemCriticalPods = true and it has scheduler.alpha.kubernetes.io/evict annotation",
 			pods: []*v1.Pod{
 				test.BuildTestPod("p16", 400, 0, n1.Name, func(pod *v1.Pod) {
 					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
@@ -649,7 +653,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			evictSystemCriticalPods: true,
 			result:                  true,
 		}, {
-			description: "Pod is evicted becasuse it has a priority higher than the configured priority threshold, but evictSystemCriticalPods = true",
+			description: "Pod is evicted because it has a priority higher than the configured priority threshold, but evictSystemCriticalPods = true",
 			pods: []*v1.Pod{
 				test.BuildTestPod("p17", 400, 0, n1.Name, func(pod *v1.Pod) {
 					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
@@ -661,7 +665,7 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			priorityThreshold:       &lowPriority,
 			result:                  true,
 		}, {
-			description: "Pod is evicted becasuse it has a priority higher than the configured priority threshold, but evictSystemCriticalPods = true and it has scheduler.alpha.kubernetes.io/evict annotation",
+			description: "Pod is evicted because it has a priority higher than the configured priority threshold, but evictSystemCriticalPods = true and it has scheduler.alpha.kubernetes.io/evict annotation",
 			pods: []*v1.Pod{
 				test.BuildTestPod("p17", 400, 0, n1.Name, func(pod *v1.Pod) {
 					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
@@ -704,6 +708,47 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			evictSystemCriticalPods: false,
 			nodeFit:                 true,
 			result:                  true,
+		}, {
+			description: "minReplicas of 2, owner with 2 replicas, evicts",
+			pods: []*v1.Pod{
+				test.BuildTestPod("p1", 1, 1, n1.Name, func(pod *v1.Pod) {
+					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
+					pod.ObjectMeta.OwnerReferences[0].UID = ownerRefUUID
+				}),
+				test.BuildTestPod("p2", 1, 1, n1.Name, func(pod *v1.Pod) {
+					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
+					pod.ObjectMeta.OwnerReferences[0].UID = ownerRefUUID
+				}),
+			},
+			minReplicas: 2,
+			result:      true,
+		}, {
+			description: "minReplicas of 3, owner with 2 replicas, no eviction",
+			pods: []*v1.Pod{
+				test.BuildTestPod("p1", 1, 1, n1.Name, func(pod *v1.Pod) {
+					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
+					pod.ObjectMeta.OwnerReferences[0].UID = ownerRefUUID
+				}),
+				test.BuildTestPod("p2", 1, 1, n1.Name, func(pod *v1.Pod) {
+					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
+					pod.ObjectMeta.OwnerReferences[0].UID = ownerRefUUID
+				}),
+			},
+			minReplicas: 3,
+			result:      false,
+		}, {
+			description: "minReplicas of 2, multiple owners, no eviction",
+			pods: []*v1.Pod{
+				test.BuildTestPod("p1", 1, 1, n1.Name, func(pod *v1.Pod) {
+					pod.ObjectMeta.OwnerReferences = append(test.GetNormalPodOwnerRefList(), test.GetNormalPodOwnerRefList()...)
+					pod.ObjectMeta.OwnerReferences[0].UID = ownerRefUUID
+				}),
+				test.BuildTestPod("p2", 1, 1, n1.Name, func(pod *v1.Pod) {
+					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
+				}),
+			},
+			minReplicas: 2,
+			result:      true,
 		},
 	}
 
@@ -741,7 +786,8 @@ func TestDefaultEvictorFilter(t *testing.T) {
 				PriorityThreshold: &api.PriorityThreshold{
 					Value: test.priorityThreshold,
 				},
-				NodeFit: test.nodeFit,
+				NodeFit:     test.nodeFit,
+				MinReplicas: test.minReplicas,
 			}
 
 			evictorPlugin, err := New(

pkg/framework/plugins/defaultevictor/types.go

@@ -33,4 +33,5 @@ type DefaultEvictorArgs struct {
 	LabelSelector           *metav1.LabelSelector  `json:"labelSelector"`
 	PriorityThreshold       *api.PriorityThreshold `json:"priorityThreshold"`
 	NodeFit                 bool                   `json:"nodeFit"`
+	MinReplicas             uint                   `json:"minReplicas"`
 }

pkg/framework/plugins/defaultevictor/validation.go

@@ -16,6 +16,8 @@ package defaultevictor
 import (
 	"fmt"
 
+	"k8s.io/klog/v2"
+
 	"k8s.io/apimachinery/pkg/runtime"
 )
 
@@ -26,5 +28,9 @@ func ValidateDefaultEvictorArgs(obj runtime.Object) error {
 		return fmt.Errorf("priority threshold misconfigured, only one of priorityThreshold fields can be set, got %v", args)
 	}
 
+	if args.MinReplicas == 1 {
+		klog.V(4).Info("DefaultEvictor minReplicas must be greater than 1 to check for min pods during eviction. This check will be ignored during eviction.")
+	}
+
 	return nil
 }

test/e2e/e2e_duplicatepods_test.go

@@ -107,6 +107,7 @@ func TestRemoveDuplicates(t *testing.T) {
 		replicasNum             int
 		beforeFunc              func(deployment *appsv1.Deployment)
 		expectedEvictedPodCount uint
+		minReplicas             uint
 	}{
 		{
 			description: "Evict Pod even Pods schedule to specific node",
@@ -135,6 +136,15 @@ func TestRemoveDuplicates(t *testing.T) {
 			},
 			expectedEvictedPodCount: 2,
 		},
+		{
+			description: "Ignores eviction with minReplicas of 4",
+			replicasNum: 3,
+			beforeFunc: func(deployment *appsv1.Deployment) {
+				deployment.Spec.Replicas = pointer.Int32(3)
+			},
+			expectedEvictedPodCount: 0,
+			minReplicas:             4,
+		},
 	}
 	for _, tc := range tests {
 		t.Run(tc.description, func(t *testing.T) {
@@ -179,6 +189,7 @@ func TestRemoveDuplicates(t *testing.T) {
 				IgnorePvcPods:           false,
 				EvictFailedBarePods:     false,
 				NodeFit:                 false,
+				MinReplicas:             tc.minReplicas,
 			}
 
 			evictorFilter, err := defaultevictor.New(