DefaultEvictor: introduce no-eviction policy

NoEvictionPolicy dictates whether a no-eviction policy is prefered or mandatory.
Needs to be used with caution as this will give users ability to protect their pods
from eviction. Which might work against enfored policies. E.g. plugins evicting pods
violating security policies.

pkg/framework/plugins/defaultevictor/defaultevictor_test.go

@@ -29,6 +29,7 @@ import (
 	"k8s.io/client-go/informers"
 	"k8s.io/client-go/kubernetes/fake"
 	"sigs.k8s.io/descheduler/pkg/api"
+	evictionutils "sigs.k8s.io/descheduler/pkg/descheduler/evictions/utils"
 	podutil "sigs.k8s.io/descheduler/pkg/descheduler/pod"
 	frameworkfake "sigs.k8s.io/descheduler/pkg/framework/fake"
 	frameworktypes "sigs.k8s.io/descheduler/pkg/framework/types"
@@ -51,6 +52,7 @@ type testCase struct {
 	minPodAge               *metav1.Duration
 	result                  bool
 	ignorePodsWithoutPDB    bool
+	noEvictionPolicy        NoEvictionPolicy
 }
 
 func TestDefaultEvictorPreEvictionFilter(t *testing.T) {
@@ -358,6 +360,29 @@ func TestDefaultEvictorFilter(t *testing.T) {
 				}),
 			},
 			result: true,
+		}, {
+			description: "Normal pod eviction with normal ownerRefs and " + evictionutils.SoftNoEvictionAnnotationKey + " annotation (preference)",
+			pods: []*v1.Pod{
+				test.BuildTestPod("p2", 400, 0, n1.Name, func(pod *v1.Pod) {
+					pod.Annotations = map[string]string{evictionutils.SoftNoEvictionAnnotationKey: ""}
+					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
+				}),
+			},
+			evictLocalStoragePods:   false,
+			evictSystemCriticalPods: false,
+			result:                  true,
+		}, {
+			description: "Normal pod eviction with normal ownerRefs and " + evictionutils.SoftNoEvictionAnnotationKey + " annotation (mandatory)",
+			pods: []*v1.Pod{
+				test.BuildTestPod("p2", 400, 0, n1.Name, func(pod *v1.Pod) {
+					pod.Annotations = map[string]string{evictionutils.SoftNoEvictionAnnotationKey: ""}
+					pod.ObjectMeta.OwnerReferences = test.GetNormalPodOwnerRefList()
+				}),
+			},
+			evictLocalStoragePods:   false,
+			evictSystemCriticalPods: false,
+			noEvictionPolicy:        MandatoryNoEvictionPolicy,
+			result:                  false,
 		}, {
 			description: "Normal pod eviction with replicaSet ownerRefs",
 			pods: []*v1.Pod{
@@ -831,6 +856,7 @@ func initializePlugin(ctx context.Context, test testCase) (frameworktypes.Plugin
 		MinReplicas:          test.minReplicas,
 		MinPodAge:            test.minPodAge,
 		IgnorePodsWithoutPDB: test.ignorePodsWithoutPDB,
+		NoEvictionPolicy:     test.noEvictionPolicy,
 	}
 
 	evictorPlugin, err := New(