perf: symmetrical pooling for zero-allocation request encoding and response decoding

Author: merchantmoh-debug

github/github.go

@@ -554,6 +554,12 @@ func WithVersion(version string) RequestOption {
 	}
 }
 
+var requestBufferPool = sync.Pool{
+	New: func() any {
+		return new(bytes.Buffer)
+	},
+}
+
 // NewRequest creates an API request. A relative URL can be provided in urlStr,
 // in which case it is resolved relative to the BaseURL of the Client.
 // Relative URLs should always be specified without a preceding slash. If
@@ -1114,12 +1120,24 @@ func (c *Client) Do(req *http.Request, v any) (*Response, error) {
 	case io.Writer:
 		_, err = io.Copy(v, resp.Body)
 	default:
-		decErr := json.NewDecoder(resp.Body).Decode(v)
-		if decErr == io.EOF {
-			decErr = nil // ignore EOF errors caused by empty response body
-		}
-		if decErr != nil {
-			err = decErr
+		respBuf := requestBufferPool.Get().(*bytes.Buffer)
+		defer func() {
+			respBuf.Reset()
+			requestBufferPool.Put(respBuf)
+		}()
+
+		_, readErr := respBuf.ReadFrom(resp.Body)
+		if readErr != nil {
+			err = readErr
+		} else if respBuf.Len() > 0 {
+			b := respBuf.Bytes()
+			decErr := json.Unmarshal(b, v)
+			if decErr != nil && len(bytes.TrimSpace(b)) == 0 {
+				decErr = nil // ignore errors caused by empty response body
+			}
+			if decErr != nil {
+				err = decErr
+			}
 		}
 	}
 	return resp, err

github/github_benchmark_test.go

@@ -0,0 +1,88 @@
+// Copyright 2026 The go-github AUTHORS. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package github
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+)
+
+// legacyDecodeResponse simulates the behavior before Symmetrical Pooling
+// (io.ReadAll -> json.Unmarshal).
+func legacyDecodeResponse(resp *http.Response, v any) error {
+	data, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return err
+	}
+	if len(data) > 0 {
+		return json.Unmarshal(data, v)
+	}
+	return nil
+}
+
+// pooledDecodeResponse simulates the new behavior with Symmetrical Pooling
+// (requestBufferPool -> ReadFrom -> json.Unmarshal).
+func pooledDecodeResponse(resp *http.Response, v any) error {
+	respBuf := requestBufferPool.Get().(*bytes.Buffer)
+	defer func() {
+		respBuf.Reset()
+		requestBufferPool.Put(respBuf)
+	}()
+
+	_, err := respBuf.ReadFrom(resp.Body)
+	if err != nil {
+		return err
+	}
+	if respBuf.Len() > 0 {
+		b := respBuf.Bytes()
+		return json.Unmarshal(b, v)
+	}
+	return nil
+}
+
+type dummyReadCloser struct {
+	io.Reader
+}
+
+func (d *dummyReadCloser) Close() error { return nil }
+
+func BenchmarkDecodeResponse_Legacy(b *testing.B) {
+	payload, _ := json.Marshal(map[string]string{"title": "benchmark_test", "body": strings.Repeat("a", 1024*500)}) // 500KB JSON
+
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		b.StopTimer()
+		resp := &http.Response{
+			Body: &dummyReadCloser{Reader: bytes.NewReader(payload)},
+		}
+		var v map[string]string
+		b.StartTimer()
+
+		_ = legacyDecodeResponse(resp, &v)
+	}
+}
+
+func BenchmarkDecodeResponse_Pooled(b *testing.B) {
+	payload, _ := json.Marshal(map[string]string{"title": "benchmark_test", "body": strings.Repeat("a", 1024*500)}) // 500KB JSON
+
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		b.StopTimer()
+		resp := &http.Response{
+			Body: &dummyReadCloser{Reader: bytes.NewReader(payload)},
+		}
+		var v map[string]string
+		b.StartTimer()
+
+		_ = pooledDecodeResponse(resp, &v)
+	}
+}