logger.V(4).Info("Cleaned up unhealthy replicas from old RSes", "count", cleanupCount)

	// Scale down old replica sets, need check maxUnavailable to ensure we can scale down
	allRSs = append(oldRSs, newRS)
	scaledDownCount, err := dc.scaleDownOldReplicaSetsForRollingUpdate(ctx, allRSs, oldRSs, deployment)
	if err != nil {
		return false, nil
	}

// 3. If there's no existing new RS and createIfNotExisted is true, create one with appropriate revision number (maxOldRevision + 1) and replicas.
// Note that the pod-template-hash will be added to adopted RSes and pods.

	}
	oldRevision, ok := newRS.Annotations[RevisionAnnotation]
	// The newRS's revision should be the greatest among all RSes. Usually, its revision number is newRevision (the max revision number
	// of all old RSes + 1). However, it's possible that some of the old RSes are deleted after the newRS revision being updated, and

// FilterReplicaSets returns replica sets that are filtered by filterFn (all returned ones should match filterFn).
func FilterReplicaSets(RSes []*apps.ReplicaSet, filterFn filterRS) []*apps.ReplicaSet {
	var filtered []*apps.ReplicaSet
	for i := range RSes {
		if filterFn(RSes[i]) {
			filtered = append(filtered, RSes[i])
		}
	}
	return filtered
}

// PodKey returns a key unique to the given pod within a cluster.