From e4f5cfa7f2cf0dae47d3c89380a64ffd3960988e Mon Sep 17 00:00:00 2001
From: Hiroya Onoe <git@onoe.dev>
Date: Thu, 18 Apr 2024 22:26:38 +0900
Subject: [PATCH] Use sync.Pools for ResourceLogs in otelloghttp transforms

---
 .../otlp/otlplog/otlploghttp/exporter.go      |  3 ++-
 .../otlp/otlplog/otlploghttp/exporter_test.go |  4 ++--
 .../otlploghttp/internal/transform/log.go     | 19 ++++++++++++++-----
 .../internal/transform/log_test.go            | 11 ++++++++++-
 4 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/exporters/otlp/otlplog/otlploghttp/exporter.go b/exporters/otlp/otlplog/otlploghttp/exporter.go
index e852b766501..cd3db1a713a 100644
--- a/exporters/otlp/otlplog/otlploghttp/exporter.go
+++ b/exporters/otlp/otlplog/otlploghttp/exporter.go
@@ -46,10 +46,11 @@ func (e *Exporter) Export(ctx context.Context, records []log.Record) error {
 	if e.stopped.Load() {
 		return nil
 	}
-	otlp := transformResourceLogs(records)
+	otlp, free := transformResourceLogs(records)
 	if otlp == nil {
 		return nil
 	}
+	defer free()
 	return e.client.Load().UploadLogs(ctx, otlp)
 }
 
diff --git a/exporters/otlp/otlplog/otlploghttp/exporter_test.go b/exporters/otlp/otlplog/otlploghttp/exporter_test.go
index 5123298f302..5cf123e6c9d 100644
--- a/exporters/otlp/otlplog/otlploghttp/exporter_test.go
+++ b/exporters/otlp/otlplog/otlploghttp/exporter_test.go
@@ -44,9 +44,9 @@ func TestExporterExport(t *testing.T) {
 
 	orig := transformResourceLogs
 	var got []log.Record
-	transformResourceLogs = func(r []log.Record) []*logpb.ResourceLogs {
+	transformResourceLogs = func(r []log.Record) ([]*logpb.ResourceLogs, func()) {
 		got = r
-		return make([]*logpb.ResourceLogs, 1)
+		return make([]*logpb.ResourceLogs, 1), func() {}
 	}
 	t.Cleanup(func() { transformResourceLogs = orig })
 
diff --git a/exporters/otlp/otlplog/otlploghttp/internal/transform/log.go b/exporters/otlp/otlplog/otlploghttp/internal/transform/log.go
index 0ad67e1f68e..26b1c9c513e 100644
--- a/exporters/otlp/otlplog/otlploghttp/internal/transform/log.go
+++ b/exporters/otlp/otlplog/otlploghttp/internal/transform/log.go
@@ -6,6 +6,7 @@
 package transform // import "go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp/internal/transform"
 
 import (
+	"sync"
 	"time"
 
 	cpb "go.opentelemetry.io/proto/slim/otlp/common/v1"
@@ -18,18 +19,26 @@ import (
 	"go.opentelemetry.io/otel/sdk/log"
 )
 
+var resourceLogsPool = sync.Pool{
+	New: func() any {
+		return []*lpb.ResourceLogs{}
+	},
+}
+
 // ResourceLogs returns an slice of OTLP ResourceLogs generated from records.
-func ResourceLogs(records []log.Record) []*lpb.ResourceLogs {
+func ResourceLogs(records []log.Record) (out []*lpb.ResourceLogs, free func()) {
 	if len(records) == 0 {
-		return nil
+		return nil, func() {}
 	}
-
 	resMap := resourceLogsMap(records)
-	out := make([]*lpb.ResourceLogs, 0, len(resMap))
+	out = resourceLogsPool.Get().([]*lpb.ResourceLogs)
 	for _, rl := range resMap {
 		out = append(out, rl)
 	}
-	return out
+	return out, func() {
+		out = out[:0:0]
+		resourceLogsPool.Put(out)
+	}
 }
 
 func resourceLogsMap(records []log.Record) map[attribute.Distinct]*lpb.ResourceLogs {
diff --git a/exporters/otlp/otlplog/otlploghttp/internal/transform/log_test.go b/exporters/otlp/otlplog/otlploghttp/internal/transform/log_test.go
index db8063e1587..7b988ab062a 100644
--- a/exporters/otlp/otlplog/otlploghttp/internal/transform/log_test.go
+++ b/exporters/otlp/otlplog/otlploghttp/internal/transform/log_test.go
@@ -163,7 +163,16 @@ var (
 
 func TestResourceLogs(t *testing.T) {
 	want := []*lpb.ResourceLogs{pbResourceLogs}
-	assert.Equal(t, want, ResourceLogs(records))
+	out, free := ResourceLogs(records)
+	assert.Equal(t, want, out)
+	free()
+	want = []*lpb.ResourceLogs{{
+		ScopeLogs: []*lpb.ScopeLogs{{
+			LogRecords: pbLogRecords[2:],
+		}},
+	}}
+	out, free = ResourceLogs(records[2:])
+	assert.Equal(t, want, out)
 }
 
 func TestSeverityNumber(t *testing.T) {