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