From a44867a9818d983b34f1ce2374346543b376a71c Mon Sep 17 00:00:00 2001
From: Kevin McConnell <kevin@37signals.com>
Date: Fri, 26 Jul 2024 14:32:03 +0100
Subject: [PATCH] Use a buffer pool when proxying

Improves performance by reducing allocations.
---
 internal/server/proxy_buffer_pool.go | 25 +++++++++++++++++++++++++
 internal/server/service.go           |  1 +
 internal/server/target.go            |  3 +++
 3 files changed, 29 insertions(+)
 create mode 100644 internal/server/proxy_buffer_pool.go

diff --git a/internal/server/proxy_buffer_pool.go b/internal/server/proxy_buffer_pool.go
new file mode 100644
index 0000000..9505b11
--- /dev/null
+++ b/internal/server/proxy_buffer_pool.go
@@ -0,0 +1,25 @@
+package server
+
+import "sync"
+
+func NewBufferPool(bufferSize int64) *BufferPool {
+	return &BufferPool{
+		pool: sync.Pool{
+			New: func() interface{} {
+				return make([]byte, bufferSize)
+			},
+		},
+	}
+}
+
+type BufferPool struct {
+	pool sync.Pool
+}
+
+func (b *BufferPool) Get() []byte {
+	return b.pool.Get().([]byte)
+}
+
+func (b *BufferPool) Put(content []byte) {
+	b.pool.Put(content)
+}
diff --git a/internal/server/service.go b/internal/server/service.go
index 0f97592..9a78b13 100644
--- a/internal/server/service.go
+++ b/internal/server/service.go
@@ -32,6 +32,7 @@ const (
 	DefaultHealthCheckTimeout  = time.Second * 5
 
 	MaxIdleConnsPerHost = 100
+	ProxyBufferSize     = 32 * KB
 
 	DefaultTargetTimeout              = time.Second * 10
 	DefaultMaxRequestMemoryBufferSize = 1 * MB
diff --git a/internal/server/target.go b/internal/server/target.go
index 901e449..1663db6 100644
--- a/internal/server/target.go
+++ b/internal/server/target.go
@@ -251,7 +251,10 @@ func (t *Target) recordTargetNameForRequest(req *http.Request) {
 }
 
 func (t *Target) createProxyHandler() http.Handler {
+	bufferPool := NewBufferPool(ProxyBufferSize)
+
 	return &httputil.ReverseProxy{
+		BufferPool:   bufferPool,
 		Rewrite:      t.Rewrite,
 		ErrorHandler: t.handleProxyError,
 		Transport: &http.Transport{