func bucketUsageMetricsPrometheus(ch chan<- prometheus.Metric) {
	objLayer := newObjectLayerFn()
	// Service not initialized yet
	if objLayer == nil {
		return
	}

	dataUsageInfo, err := loadDataUsageFromBackend(GlobalContext, objLayer)
	if err != nil {
		return
	}
	// data usage has not captured any data yet.
	if dataUsageInfo.LastUpdate.IsZero() {
		return
	}