apiRequests5xxErrorsTotalMD,
			apiRequests4xxErrorsTotalMD,
			apiRequestsCanceledTotalMD,

			apiRequestsTTFBSecondsDistributionMD,

			apiTrafficSentBytesMD,
			apiTrafficRecvBytesMD,
		},
		JoinLoaders(loadAPIRequestsHTTPMetrics, loadAPIRequestsTTFBMetrics,
			loadAPIRequestsNetworkMetrics),
	)

	bucketAPIMG := NewBucketMetricsGroup(bucketAPICollectorPath,
		[]MetricDescriptor{
			bucketAPITrafficRecvBytesMD,

// 500 Internal Server Error.
type MetricsLoaderFn func(context.Context, MetricValues, *metricsCache) error

// JoinLoaders - joins multiple loaders into a single loader. The returned
// loader will call each of the given loaders in order. If any of the loaders
// return an error, the returned loader will return that error.
func JoinLoaders(loaders ...MetricsLoaderFn) MetricsLoaderFn {
	return func(ctx context.Context, m MetricValues, c *metricsCache) error {