From f77011fd34c40d148da36f8e5744080b5f3e6cd8 Mon Sep 17 00:00:00 2001
From: Pedro Tanaka <pedro.tanaka@shopify.com>
Date: Fri, 11 Nov 2022 16:02:13 +0100
Subject: [PATCH] Allow creation of native histograms

Signed-off-by: Pedro Tanaka <pedro.tanaka@shopify.com>
---
 pkg/mapper/mapper.go     | 10 +++++++++-
 pkg/registry/registry.go | 18 +++++++++++++++---
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/pkg/mapper/mapper.go b/pkg/mapper/mapper.go
index 879f18c..0f17165 100644
--- a/pkg/mapper/mapper.go
+++ b/pkg/mapper/mapper.go
@@ -64,7 +64,9 @@ type SummaryOptions struct {
 }
 
 type HistogramOptions struct {
-	Buckets []float64 `yaml:"buckets"`
+	Buckets                     []float64 `yaml:"buckets"`
+	NativeHistogramBucketFactor float64   `yaml:"native_histogram_bucket_factor"`
+	NativeHistogramMaxBuckets   uint32    `yaml:"native_histogram_max_buckets"`
 }
 
 type metricObjective struct {
@@ -88,6 +90,12 @@ func (m *MetricMapper) InitFromYAMLString(fileContents string) error {
 	if len(n.Defaults.HistogramOptions.Buckets) == 0 {
 		n.Defaults.HistogramOptions.Buckets = prometheus.DefBuckets
 	}
+	if n.Defaults.HistogramOptions.NativeHistogramBucketFactor == 0 {
+		n.Defaults.HistogramOptions.NativeHistogramBucketFactor = 1.1
+	}
+	if n.Defaults.HistogramOptions.NativeHistogramMaxBuckets <= 0 {
+		n.Defaults.HistogramOptions.NativeHistogramMaxBuckets = 256
+	}
 
 	if len(n.Defaults.SummaryOptions.Quantiles) == 0 {
 		n.Defaults.SummaryOptions.Quantiles = defaultQuantiles
diff --git a/pkg/registry/registry.go b/pkg/registry/registry.go
index 87d39a1..825cb14 100644
--- a/pkg/registry/registry.go
+++ b/pkg/registry/registry.go
@@ -274,10 +274,22 @@ func (r *Registry) GetHistogram(metricName string, labels prometheus.Labels, hel
 		if mapping.HistogramOptions != nil && len(mapping.HistogramOptions.Buckets) > 0 {
 			buckets = mapping.HistogramOptions.Buckets
 		}
+
+		bucketFactor := r.Mapper.Defaults.HistogramOptions.NativeHistogramBucketFactor
+		if mapping.HistogramOptions != nil && mapping.HistogramOptions.NativeHistogramBucketFactor > 0 {
+			bucketFactor = mapping.HistogramOptions.NativeHistogramBucketFactor
+		}
+
+		maxBuckets := r.Mapper.Defaults.HistogramOptions.NativeHistogramMaxBuckets
+		if mapping.HistogramOptions != nil && mapping.HistogramOptions.NativeHistogramMaxBuckets > 0 {
+			maxBuckets = mapping.HistogramOptions.NativeHistogramMaxBuckets
+		}
 		histogramVec = prometheus.NewHistogramVec(prometheus.HistogramOpts{
-			Name:    metricName,
-			Help:    help,
-			Buckets: buckets,
+			Name:                           metricName,
+			Help:                           help,
+			Buckets:                        buckets,
+			NativeHistogramBucketFactor:    bucketFactor,
+			NativeHistogramMaxBucketNumber: maxBuckets,
 		}, labelNames)
 
 		if err := r.Registerer.Register(uncheckedCollector{histogramVec}); err != nil {