skip eviction when pod creation time is below minPodAge threshold setting (#1475)

* skip eviction when pod creation time is below minPodAge threshold setting

In the default initialization phase of the descheduler, add a new
constraint to not evict pods that creation time is below minPodAge
threshold.

Added value:

- Avoid crazy pod movement when the autoscaler scales up and down.

- Avoid evicting pods when they are warming up.

- Decreases the overall cost of eviction as no pod will be evicted
  before doing significant amount of work.

- Guard against scheduling. Descheduling loops in situations where
  the descheduler has a different node fit logic from scheduler,
  like not considering topology spread constraints.

* Use *time.Duration instead of uint for MinPodAge type

* Remove '(in minutes)' from default evictor configuration table

* make fmt

* Add explicit name for Duration field

* Use Duration.String()

pkg/framework/plugins/defaultevictor/defaultevictor_test.go

@@ -17,6 +17,9 @@ import (
 	"context"
 	"fmt"
 	"testing"
+	"time"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 
 	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
@@ -42,6 +45,7 @@ type testCase struct {
 	priorityThreshold       *int32
 	nodeFit                 bool
 	minReplicas             uint
+	minPodAge               *metav1.Duration
 	result                  bool
 }
 
@@ -326,6 +330,8 @@ func TestDefaultEvictorFilter(t *testing.T) {
 	lowPriority := int32(800)
 	highPriority := int32(900)
 
+	minPodAge := metav1.Duration{Duration: 50 * time.Minute}
+
 	nodeTaintKey := "hardware"
 	nodeTaintValue := "gpu"
 
@@ -701,6 +707,38 @@ func TestDefaultEvictorFilter(t *testing.T) {
 			},
 			minReplicas: 2,
 			result:      true,
+		}, {
+			description: "minPodAge of 50, pod created 10 minutes ago, no eviction",
+			pods: []*v1.Pod{
+				test.BuildTestPod("p1", 1, 1, n1.Name, func(pod *v1.Pod) {
+					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
+					podStartTime := metav1.Now().Add(time.Minute * time.Duration(-10))
+					pod.Status.StartTime = &metav1.Time{Time: podStartTime}
+				}),
+			},
+			minPodAge: &minPodAge,
+			result:    false,
+		}, {
+			description: "minPodAge of 50, pod created 60 minutes ago, evicts",
+			pods: []*v1.Pod{
+				test.BuildTestPod("p1", 1, 1, n1.Name, func(pod *v1.Pod) {
+					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
+					podStartTime := metav1.Now().Add(time.Minute * time.Duration(-60))
+					pod.Status.StartTime = &metav1.Time{Time: podStartTime}
+				}),
+			},
+			minPodAge: &minPodAge,
+			result:    true,
+		}, {
+			description: "nil minPodAge, pod created 60 minutes ago, evicts",
+			pods: []*v1.Pod{
+				test.BuildTestPod("p1", 1, 1, n1.Name, func(pod *v1.Pod) {
+					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
+					podStartTime := metav1.Now().Add(time.Minute * time.Duration(-60))
+					pod.Status.StartTime = &metav1.Time{Time: podStartTime}
+				}),
+			},
+			result: true,
 		},
 	}
 
@@ -797,6 +835,7 @@ func initializePlugin(ctx context.Context, test testCase) (frameworktypes.Plugin
 		},
 		NodeFit:     test.nodeFit,
 		MinReplicas: test.minReplicas,
+		MinPodAge:   test.minPodAge,
 	}
 
 	evictorPlugin, err := New(