// synchronization used internally.
		select {
		case <-ticker.C:
			ttfbHist.With(prometheus.Labels{"api": obs.label}).Observe(obs.val)
		}
	}

	metrics := getHistogramMetrics(ttfbHist, getBucketTTFBDistributionMD(), false)
	// additional labels for +Inf for all histogram metrics
	if expPoints := len(labels) * (len(histBuckets) + 1); expPoints != len(metrics) {

		Name:      tierRequestsFailure,
		Help:      "Number of requests to download object from warm tier that failed",
		Type:      counterMetric,
	}
)

func (t *tierMetrics) Report() []MetricV2 {
	metrics := getHistogramMetrics(t.histogram, tierTTLBMD, true)
	t.RLock()
	defer t.RUnlock()
	for tier, stat := range t.requestsCount {
		metrics = append(metrics, MetricV2{
			Description:    tierRequestsSuccessMD,

) {
	if _, ok := m.descriptors[name]; !ok {
		panic(fmt.Sprintf("metric has no description: %s", name))
	}
	dummyDesc := MetricDescription{}
	metricsV2 := getHistogramMetrics(hist, dummyDesc, false)
	for _, metric := range metricsV2 {
		// If a bucket filter is provided, only add metrics for the given
		// buckets.
		if len(bucketFilter) > 0 {

		})
		return
	})
	return mg
}

// getHistogramMetrics fetches histogram metrics and returns it in a []Metric
// Note: Typically used in MetricGroup.RegisterRead
//
// The last parameter is added for compatibility - if true it lowercases the
// `api` label values.
func getHistogramMetrics(hist *prometheus.HistogramVec, desc MetricDescription, toLowerAPILabels bool) []MetricV2 {