Allow simulator to persist changes in cluster snapshot

cluster-autoscaler/core/scaledown/legacy/legacy.go

@@ -65,7 +65,7 @@ type ScaleDown struct {
 // NewScaleDown builds new ScaleDown object.
 func NewScaleDown(context *context.AutoscalingContext, processors *processors.AutoscalingProcessors, clusterStateRegistry *clusterstate.ClusterStateRegistry, ndt *deletiontracker.NodeDeletionTracker) *ScaleDown {
 	usageTracker := simulator.NewUsageTracker()
-	removalSimulator := simulator.NewRemovalSimulator(context.ListerRegistry, context.ClusterSnapshot, context.PredicateChecker, usageTracker)
+	removalSimulator := simulator.NewRemovalSimulator(context.ListerRegistry, context.ClusterSnapshot, context.PredicateChecker, usageTracker, false)
 	unremovableNodes := unremovable.NewNodes()
 	return &ScaleDown{
 		context:              context,

cluster-autoscaler/simulator/cluster.go

@@ -101,15 +101,17 @@ type RemovalSimulator struct {
 	clusterSnapshot  ClusterSnapshot
 	predicateChecker PredicateChecker
 	usageTracker     *UsageTracker
+	canPersist       bool
 }
 
 // NewRemovalSimulator returns a new RemovalSimulator.
-func NewRemovalSimulator(listers kube_util.ListerRegistry, clusterSnapshot ClusterSnapshot, predicateChecker PredicateChecker, usageTracker *UsageTracker) *RemovalSimulator {
+func NewRemovalSimulator(listers kube_util.ListerRegistry, clusterSnapshot ClusterSnapshot, predicateChecker PredicateChecker, usageTracker *UsageTracker, persistSuccessfulSimulations bool) *RemovalSimulator {
 	return &RemovalSimulator{
 		listers:          listers,
 		clusterSnapshot:  clusterSnapshot,
 		predicateChecker: predicateChecker,
 		usageTracker:     usageTracker,
+		canPersist:       persistSuccessfulSimulations,
 	}
 }
 
@@ -174,7 +176,9 @@ func (r *RemovalSimulator) CheckNodeRemoval(
 		return nil, &UnremovableNode{Node: nodeInfo.Node(), Reason: UnexpectedError}
 	}
 
-	err = r.findPlaceFor(nodeName, podsToRemove, destinationMap, oldHints, newHints, timestamp)
+	err = r.withForkedSnapshot(func() error {
+		return r.findPlaceFor(nodeName, podsToRemove, destinationMap, oldHints, newHints, timestamp)
+	})
 	if err != nil {
 		klog.V(2).Infof("node %s is not suitable for removal: %v", nodeName, err)
 		return nil, &UnremovableNode{Node: nodeInfo.Node(), Reason: NoPlaceToMovePods}
@@ -205,19 +209,29 @@ func (r *RemovalSimulator) FindEmptyNodesToRemove(candidates []string, timestamp
 	return result
 }
 
-func (r *RemovalSimulator) findPlaceFor(removedNode string, pods []*apiv1.Pod, nodes map[string]bool,
-	oldHints map[string]string, newHints map[string]string, timestamp time.Time) error {
-
-	if err := r.clusterSnapshot.Fork(); err != nil {
+func (r *RemovalSimulator) withForkedSnapshot(f func() error) (err error) {
+	if err = r.clusterSnapshot.Fork(); err != nil {
 		return err
 	}
 	defer func() {
-		err := r.clusterSnapshot.Revert()
-		if err != nil {
-			klog.Fatalf("Got error when calling ClusterSnapshot.Revert(); %v", err)
+		if err == nil && r.canPersist {
+			cleanupErr := r.clusterSnapshot.Commit()
+			if cleanupErr != nil {
+				klog.Fatalf("Got error when calling ClusterSnapshot.Commit(); %v", cleanupErr)
+			}
+		} else {
+			cleanupErr := r.clusterSnapshot.Revert()
+			if cleanupErr != nil {
+				klog.Fatalf("Got error when calling ClusterSnapshot.Revert(); %v", cleanupErr)
+			}
 		}
 	}()
+	err = f()
+	return err
+}
 
+func (r *RemovalSimulator) findPlaceFor(removedNode string, pods []*apiv1.Pod, nodes map[string]bool,
+	oldHints map[string]string, newHints map[string]string, timestamp time.Time) error {
 	podKey := func(pod *apiv1.Pod) string {
 		return fmt.Sprintf("%s/%s", pod.Namespace, pod.Name)
 	}

cluster-autoscaler/simulator/cluster_test.go

@@ -58,7 +58,7 @@ func TestFindPlaceAllOk(t *testing.T) {
 		[]*apiv1.Node{node1, node2},
 		[]*apiv1.Pod{pod1})
 
-	err = NewRemovalSimulator(nil, clusterSnapshot, predicateChecker, NewUsageTracker()).findPlaceFor(
+	err = NewRemovalSimulator(nil, clusterSnapshot, predicateChecker, NewUsageTracker(), false).findPlaceFor(
 		"x",
 		[]*apiv1.Pod{new1, new2},
 		destinations,
@@ -96,7 +96,7 @@ func TestFindPlaceAllBas(t *testing.T) {
 		[]*apiv1.Node{node1, node2},
 		[]*apiv1.Pod{pod1})
 
-	err = NewRemovalSimulator(nil, clusterSnapshot, predicateChecker, NewUsageTracker()).findPlaceFor(
+	err = NewRemovalSimulator(nil, clusterSnapshot, predicateChecker, NewUsageTracker(), false).findPlaceFor(
 		"nbad",
 		[]*apiv1.Pod{new1, new2, new3},
 		destinations,
@@ -129,7 +129,7 @@ func TestFindNone(t *testing.T) {
 		[]*apiv1.Node{node1, node2},
 		[]*apiv1.Pod{pod1})
 
-	err = NewRemovalSimulator(nil, clusterSnapshot, predicateChecker, NewUsageTracker()).findPlaceFor(
+	err = NewRemovalSimulator(nil, clusterSnapshot, predicateChecker, NewUsageTracker(), false).findPlaceFor(
 		"x",
 		[]*apiv1.Pod{},
 		destinations,
@@ -162,7 +162,7 @@ func TestFindEmptyNodes(t *testing.T) {
 	clusterSnapshot := NewBasicClusterSnapshot()
 	InitializeClusterSnapshotOrDie(t, clusterSnapshot, []*apiv1.Node{nodes[0], nodes[1], nodes[2], nodes[3]}, []*apiv1.Pod{pod1, pod2})
 	testTime := time.Date(2020, time.December, 18, 17, 0, 0, 0, time.UTC)
-	r := NewRemovalSimulator(nil, clusterSnapshot, nil, nil)
+	r := NewRemovalSimulator(nil, clusterSnapshot, nil, nil, false)
 	emptyNodes := r.FindEmptyNodesToRemove(nodeNames, testTime)
 	assert.Equal(t, []string{nodeNames[0], nodeNames[2], nodeNames[3]}, emptyNodes)
 }
@@ -309,7 +309,7 @@ func TestFindNodesToRemove(t *testing.T) {
 				destinations = append(destinations, node.Name)
 			}
 			InitializeClusterSnapshotOrDie(t, clusterSnapshot, test.allNodes, test.pods)
-			r := NewRemovalSimulator(registry, clusterSnapshot, predicateChecker, tracker)
+			r := NewRemovalSimulator(registry, clusterSnapshot, predicateChecker, tracker, false)
 			toRemove, unremovable, _, err := r.FindNodesToRemove(
 				test.candidates, destinations, map[string]string{},
 				time.Now(), []*policyv1.PodDisruptionBudget{})