why RemoveNodeFromTracker clean the passed utilization map?

[duyawen8]

Which component are you using?: cluster-autoscaler

What version of the component are you using?: cluster-autoscaler-1.23.0

Component version: cluster-autoscaler-1.23.0

What k8s version are you using (kubectl version)?:

kubectl version Output

$ kubectl version

What environment is this in?:
self-build kubernetes cluster, not cloud provider cluster

What did you expect to happen?: don't reset unneed time

What happened instead?: reset unneed time

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know?:

1. Why clean unneededNodes when the number of using or used node exceed 50? What is the purpose? It makes our cluster scale-down slow because clean means reset unneeded time.

cluster-autoscaler/core/scale_down.go

// Nothing super-bad should happen if the node is removed from tracker prematurely.
simulator.RemoveNodeFromTracker(sd.usageTracker, toRemove.Node.Name, sd.unneededNodes)
nodeDeletionStart := time.Now()

cluster-autoscaler/simulator/tracker.go

// RemoveNodeFromTracker removes node from tracker and also cleans the passed utilization map.
func RemoveNodeFromTracker(tracker *UsageTracker, node string, utilization map[string]time.Time) {
	klog.V(4).Infof("Removing node %s from utilization map", node)
	keysToRemove := make([]string, 0)
	if mainRecord, found := tracker.Get(node); found {
		if mainRecord.usingTooMany {
			klog.V(4).Infof("Node %s is using too many nodes, removing all keys from utilization map", node)
			keysToRemove = getAllKeys(utilization)
		} else {
		usingloop:
			for usedNode := range mainRecord.using {
				if usedNodeRecord, found := tracker.Get(usedNode); found {
					if usedNodeRecord.usedByTooMany {
						klog.V(4).Infof("Node %s is used by too many nodes, removing all keys from utilization map", usedNode)
						keysToRemove = getAllKeys(utilization)
						break usingloop
					} else {
						for anotherNode := range usedNodeRecord.usedBy {
							keysToRemove = append(keysToRemove, anotherNode)
						}
					}
				}
			}
		}
	}
	tracker.Unregister(node)
	delete(utilization, node)
	for _, key := range keysToRemove {
		delete(utilization, key)
	}
}

[adrianmoisey]

/area cluster-autoscaler