mg.descriptorMap = make(map[MetricName]MetricDescriptor, len(mg.Descriptors))
	for _, desc := range mg.Descriptors {
		mg.descriptorMap[desc.Name] = desc
	}
}

// SetCache is a helper to initialize MetricsGroup. It sets the cache object.
func (mg *MetricsGroup) SetCache(c *metricsCache) {
	mg.cache = c

		if !strings.HasPrefix(string(mg.CollectorPath), clusterBasePath) {
			mg.AddExtraLabels(
				serverName, globalLocalNodeName,
				// poolIndex, strconv.Itoa(globalLocalPoolIdx),
			)
		}
		mg.SetCache(metricsCache)
		if mg.IsBucketMetricsGroup() {
			bucketMGMap[mg.CollectorPath] = mg
		} else {
			mgMap[mg.CollectorPath] = mg
		}
	}