Merge pull request #520 from KohlsTechnology/statefulset-docs

Document That Descheduler Considers StatefulSets For Eviction

README.md

@@ -130,15 +130,17 @@ strategies:
 
 ### RemoveDuplicates
 
-This strategy makes sure that there is only one pod associated with a Replica Set (RS),
-Replication Controller (RC), Deployment, or Job running on the same node. If there are more,
+This strategy makes sure that there is only one pod associated with a ReplicaSet (RS),
+ReplicationController (RC), StatefulSet, or Job running on the same node. If there are more,
 those duplicate pods are evicted for better spreading of pods in a cluster. This issue could happen
 if some nodes went down due to whatever reasons, and pods on them were moved to other nodes leading to
 more than one pod associated with a RS or RC, for example, running on the same node. Once the failed nodes
 are ready again, this strategy could be enabled to evict those duplicate pods.
 
-It provides one optional parameter, `ExcludeOwnerKinds`, which is a list of OwnerRef `Kind`s. If a pod
-has any of these `Kind`s listed as an `OwnerRef`, that pod will not be considered for eviction.
+It provides one optional parameter, `excludeOwnerKinds`, which is a list of OwnerRef `Kind`s. If a pod
+has any of these `Kind`s listed as an `OwnerRef`, that pod will not be considered for eviction. Note that
+pods created by Deployments are considered for eviction by this strategy. The `excludeOwnerKinds` parameter
+should include `ReplicaSet` to have pods created by Deployments excluded.
 
 **Parameters:**
 
@@ -546,7 +548,7 @@ strategies:
 When the descheduler decides to evict pods from a node, it employs the following general mechanism:
 
 * [Critical pods](https://kubernetes.io/docs/tasks/administer-cluster/guaranteed-scheduling-critical-addon-pods/) (with priorityClassName set to system-cluster-critical or system-node-critical) are never evicted.
-* Pods (static or mirrored pods or stand alone pods) not part of an RC, RS, Deployment or Job are
+* Pods (static or mirrored pods or stand alone pods) not part of an ReplicationController, ReplicaSet(Deployment), StatefulSet, or Job are
 never evicted because these pods won't be recreated.
 * Pods associated with DaemonSets are never evicted.
 * Pods with local storage are never evicted (unless `evictLocalStoragePods: true` is set)

pkg/descheduler/evictions/evictions_test.go

@@ -236,6 +236,21 @@ func TestIsEvictable(t *testing.T) {
 			evictLocalStoragePods: false,
 			priorityThreshold:     &lowPriority,
 			result:                true,
+		}, {
+			pod: test.BuildTestPod("p16", 400, 0, n1.Name, nil),
+			runBefore: func(pod *v1.Pod) {
+				pod.ObjectMeta.OwnerReferences = test.GetStatefulSetOwnerRefList()
+			},
+			evictLocalStoragePods: false,
+			result:                true,
+		}, {
+			pod: test.BuildTestPod("p17", 400, 0, n1.Name, nil),
+			runBefore: func(pod *v1.Pod) {
+				pod.Annotations = map[string]string{"descheduler.alpha.kubernetes.io/evict": "true"}
+				pod.ObjectMeta.OwnerReferences = test.GetStatefulSetOwnerRefList()
+			},
+			evictLocalStoragePods: false,
+			result:                true,
 		},
 	}
 

test/test_utils.go

@@ -79,6 +79,13 @@ func GetReplicaSetOwnerRefList() []metav1.OwnerReference {
 	return ownerRefList
 }
 
+// GetStatefulSetOwnerRefList returns the ownerRef needed for statefulset pod.
+func GetStatefulSetOwnerRefList() []metav1.OwnerReference {
+	ownerRefList := make([]metav1.OwnerReference, 0)
+	ownerRefList = append(ownerRefList, metav1.OwnerReference{Kind: "StatefulSet", APIVersion: "v1", Name: "statefulset-1"})
+	return ownerRefList
+}
+
 // GetDaemonSetOwnerRefList returns the ownerRef needed for daemonset pod.
 func GetDaemonSetOwnerRefList() []metav1.OwnerReference {
 	ownerRefList := make([]metav1.OwnerReference, 0)
@@ -142,6 +149,11 @@ func SetRSOwnerRef(pod *v1.Pod) {
 	pod.ObjectMeta.OwnerReferences = GetReplicaSetOwnerRefList()
 }
 
+// SetSSOwnerRef sets the given pod's owner to StatefulSet
+func SetSSOwnerRef(pod *v1.Pod) {
+	pod.ObjectMeta.OwnerReferences = GetStatefulSetOwnerRefList()
+}
+
 // SetDSOwnerRef sets the given pod's owner to DaemonSet
 func SetDSOwnerRef(pod *v1.Pod) {
 	pod.ObjectMeta.OwnerReferences = GetDaemonSetOwnerRefList()