From 5e8eb855bf3c6507715edd12ded5c6a950dd6104 Mon Sep 17 00:00:00 2001
From: Aaron Clawson <3766680+MadVikingGod@users.noreply.github.com>
Date: Thu, 2 Feb 2023 12:16:25 -0600
Subject: [PATCH] Add a benchmark for histogram allocations (#3635)

Co-authored-by: Chester Cheung <cheung.zhy.csu@gmail.com>
---
 sdk/metric/benchmark_test.go | 42 ++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/sdk/metric/benchmark_test.go b/sdk/metric/benchmark_test.go
index c7bf12beb..0a75079d2 100644
--- a/sdk/metric/benchmark_test.go
+++ b/sdk/metric/benchmark_test.go
@@ -16,10 +16,12 @@ package metric // import "go.opentelemetry.io/otel/sdk/metric"
 
 import (
 	"context"
+	"fmt"
 	"testing"
 
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/metric/instrument"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
 func benchCounter(b *testing.B, views ...View) (context.Context, Reader, instrument.Int64Counter) {
@@ -105,3 +107,43 @@ func BenchmarkCounterCollectTenAttrs(b *testing.B) {
 		_, _ = rdr.Collect(ctx)
 	}
 }
+
+func BenchmarkCollectHistograms(b *testing.B) {
+	b.Run("1", benchCollectHistograms(1))
+	b.Run("5", benchCollectHistograms(5))
+	b.Run("10", benchCollectHistograms(10))
+	b.Run("25", benchCollectHistograms(25))
+}
+
+func benchCollectHistograms(count int) func(*testing.B) {
+	ctx := context.Background()
+	r := NewManualReader()
+	mtr := NewMeterProvider(
+		WithReader(r),
+	).Meter("sdk/metric/bench/histogram")
+
+	for i := 0; i < count; i++ {
+		name := fmt.Sprintf("fake data %d", i)
+		h, _ := mtr.Int64Histogram(name)
+
+		h.Record(ctx, 1)
+	}
+
+	// Store bechmark results in a closure to prevent the compiler from
+	// inlining and skipping the function.
+	var (
+		collectedMetrics metricdata.ResourceMetrics
+	)
+
+	return func(b *testing.B) {
+		b.ReportAllocs()
+		b.ResetTimer()
+
+		for n := 0; n < b.N; n++ {
+			collectedMetrics, _ = r.Collect(ctx)
+			if len(collectedMetrics.ScopeMetrics[0].Metrics) != count {
+				b.Fatalf("got %d metrics, want %d", len(collectedMetrics.ScopeMetrics[0].Metrics), count)
+			}
+		}
+	}
+}