pass list of destination names, not map

Author: aleksandra-malinowska

cluster-autoscaler/core/scale_down.go

@@ -417,10 +417,6 @@ func (sd *ScaleDown) UpdateUnneededNodes(
 		// This should never happen, List() returns err only because scheduler interface requires it.
 		return errors.ToAutoscalerError(errors.InternalError, err)
 	}
-	destinations := make(map[string]bool, len(destinationNodes))
-	for _, destination := range destinationNodes {
-		destinations[destination.Name] = true
-	}
 
 	sd.updateUnremovableNodes()
 
@@ -500,6 +496,11 @@ func (sd *ScaleDown) UpdateUnneededNodes(
 	// Phase2 - check which nodes can be probably removed using fast drain.
 	currentCandidates, currentNonCandidates := sd.chooseCandidates(currentlyUnneededNonEmptyNodes)
 
+	destinations := make([]string, 0, len(destinationNodes))
+	for _, destinationNode := range destinationNodes {
+		destinations = append(destinations, destinationNode.Name)
+	}
+
 	// Look for nodes to remove in the current candidates
 	nodesToRemove, unremovable, newHints, simulatorErr := simulator.FindNodesToRemove(
 		currentCandidates,
@@ -751,7 +752,7 @@ func (sd *ScaleDown) TryToScaleDown(pdbs []*policyv1.PodDisruptionBudget, curren
 	}
 
 	nodesWithoutMaster := filterOutMasters(allNodeInfos)
-	nodesWithoutMasterNames := make(map[string]bool, len(nodesWithoutMaster))
+	nodesWithoutMasterNames := make([]string, 0, len(nodesWithoutMaster))
 
 	candidateNames := make([]string, 0)
 	readinessMap := make(map[string]bool)
@@ -771,7 +772,7 @@ func (sd *ScaleDown) TryToScaleDown(pdbs []*policyv1.PodDisruptionBudget, curren
 	resourcesWithLimits := resourceLimiter.GetResources()
 	for _, nodeInfo := range nodesWithoutMaster {
 		node := nodeInfo.Node()
-		nodesWithoutMasterNames[node.Name] = true
+		nodesWithoutMasterNames = append(nodesWithoutMasterNames, node.Name)
 
 		unneededSince, found := sd.unneededNodes[node.Name]
 		if !found {

cluster-autoscaler/simulator/cluster.go

@@ -113,7 +113,7 @@ type UtilizationInfo struct {
 // rescheduling location for each of the pods.
 func FindNodesToRemove(
 	candidates []string,
-	destinations map[string]bool,
+	destinations []string,
 	listers kube_util.ListerRegistry,
 	clusterSnapshot ClusterSnapshot,
 	predicateChecker PredicateChecker,
@@ -134,6 +134,11 @@ func FindNodesToRemove(
 	}
 	newHints := make(map[string]string, len(oldHints))
 
+	destinationMap := make(map[string]bool, len(destinations))
+	for _, destination := range destinations {
+		destinationMap[destination] = true
+	}
+
 candidateloop:
 	for _, nodeName := range candidates {
 		nodeInfo, err := clusterSnapshot.NodeInfos().Get(nodeName)
@@ -145,7 +150,7 @@ candidateloop:
 		var podsToRemove []*apiv1.Pod
 		var blockingPod *drain.BlockingPod
 
-		if _, found := destinations[nodeName]; !found {
+		if _, found := destinationMap[nodeName]; !found {
 			klog.V(2).Infof("%s: nodeInfo for %s not found", evaluationType, nodeName)
 			unremovable = append(unremovable, &UnremovableNode{Node: nodeInfo.Node(), Reason: UnexpectedError})
 			continue candidateloop
@@ -169,7 +174,7 @@ candidateloop:
 			continue candidateloop
 		}
 
-		findProblems := findPlaceFor(nodeName, podsToRemove, destinations, clusterSnapshot,
+		findProblems := findPlaceFor(nodeName, podsToRemove, destinationMap, clusterSnapshot,
 			predicateChecker, oldHints, newHints, usageTracker, timestamp)
 
 		if findProblems == nil {

cluster-autoscaler/simulator/cluster_test.go

@@ -369,9 +369,9 @@ func TestFindNodesToRemove(t *testing.T) {
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			destinations := map[string]bool{}
+			destinations := make([]string, 0, len(test.allNodes))
 			for _, node := range test.allNodes {
-				destinations[node.Name] = true
+				destinations = append(destinations, node.Name)
 			}
 			InitializeClusterSnapshotOrDie(t, clusterSnapshot, test.allNodes, test.pods)
 			toRemove, unremovable, _, err := FindNodesToRemove(