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.go

@@ -18,6 +18,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"time"
 
 	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -64,6 +65,7 @@ func HaveEvictAnnotation(pod *v1.Pod) bool {
 }
 
 // New builds plugin from its arguments while passing a handle
+// nolint: gocyclo
 func New(args runtime.Object, handle frameworktypes.Handle) (frameworktypes.Plugin, error) {
 	defaultEvictorArgs, ok := args.(*DefaultEvictorArgs)
 	if !ok {
@@ -185,6 +187,14 @@ func New(args runtime.Object, handle frameworktypes.Handle) (frameworktypes.Plug
 		})
 	}
 
+	if defaultEvictorArgs.MinPodAge != nil {
+		ev.constraints = append(ev.constraints, func(pod *v1.Pod) error {
+			if pod.Status.StartTime == nil || time.Since(pod.Status.StartTime.Time) < defaultEvictorArgs.MinPodAge.Duration {
+				return fmt.Errorf("pod age is not older than MinPodAge: %s seconds", defaultEvictorArgs.MinPodAge.String())
+			}
+			return nil
+		})
+	}
 	return ev, nil
 }