From 97577c07a57b2c9160d927825fbb01cb2912a46b Mon Sep 17 00:00:00 2001
From: Manuel de Brito Fontes <aledbf@gmail.com>
Date: Tue, 7 Nov 2017 21:37:35 -0300
Subject: [PATCH] Include a buffer pool to improve memory usage

---
 .../controller/template/buffer_pool.go        | 51 +++++++++++++++++++
 .../ingress/controller/template/template.go   | 21 +++-----
 2 files changed, 58 insertions(+), 14 deletions(-)
 create mode 100644 internal/ingress/controller/template/buffer_pool.go

diff --git a/internal/ingress/controller/template/buffer_pool.go b/internal/ingress/controller/template/buffer_pool.go
new file mode 100644
index 000000000..e0a1f287c
--- /dev/null
+++ b/internal/ingress/controller/template/buffer_pool.go
@@ -0,0 +1,51 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package template
+
+import (
+	"bytes"
+	"sync"
+)
+
+// BufferPool defines a Pool of Buffers
+type BufferPool struct {
+	sync.Pool
+}
+
+// NewBufferPool creates a new BufferPool with a custom buffer size
+func NewBufferPool(s int) *BufferPool {
+	return &BufferPool{
+		Pool: sync.Pool{
+			New: func() interface{} {
+				b := bytes.NewBuffer(make([]byte, s))
+				b.Reset()
+				return b
+			},
+		},
+	}
+}
+
+// Get returns a Buffer from the pool
+func (bp *BufferPool) Get() *bytes.Buffer {
+	return bp.Pool.Get().(*bytes.Buffer)
+}
+
+// Put resets ans returns a Buffer to the pool
+func (bp *BufferPool) Put(b *bytes.Buffer) {
+	b.Reset()
+	bp.Pool.Put(b)
+}
diff --git a/internal/ingress/controller/template/template.go b/internal/ingress/controller/template/template.go
index 72de61cc2..078a05a0e 100644
--- a/internal/ingress/controller/template/template.go
+++ b/internal/ingress/controller/template/template.go
@@ -17,7 +17,6 @@ limitations under the License.
 package template
 
 import (
-	"bytes"
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
@@ -52,7 +51,7 @@ const (
 type Template struct {
 	tmpl *text_template.Template
 	fw   watch.FileWatcher
-	s    int
+	bp   *BufferPool
 }
 
 //NewTemplate returns a new Template instance or an
@@ -70,7 +69,7 @@ func NewTemplate(file string, onChange func()) (*Template, error) {
 	return &Template{
 		tmpl: tmpl,
 		fw:   fw,
-		s:    defBufferSize,
+		bp:   NewBufferPool(defBufferSize),
 	}, nil
 }
 
@@ -82,15 +81,11 @@ func (t *Template) Close() {
 // Write populates a buffer using a template with NGINX configuration
 // and the servers and upstreams created by Ingress rules
 func (t *Template) Write(conf config.TemplateConfig) ([]byte, error) {
-	tmplBuf := bytes.NewBuffer(make([]byte, 0, t.s))
-	outCmdBuf := bytes.NewBuffer(make([]byte, 0, t.s))
+	tmplBuf := t.bp.Get()
+	defer t.bp.Put(tmplBuf)
 
-	defer func() {
-		if t.s < tmplBuf.Cap() {
-			glog.V(2).Infof("adjusting template buffer size from %v to %v", t.s, tmplBuf.Cap())
-			t.s = tmplBuf.Cap()
-		}
-	}()
+	outCmdBuf := t.bp.Get()
+	defer t.bp.Put(outCmdBuf)
 
 	if glog.V(3) {
 		b, err := json.Marshal(conf)
@@ -115,9 +110,7 @@ func (t *Template) Write(conf config.TemplateConfig) ([]byte, error) {
 		return tmplBuf.Bytes(), nil
 	}
 
-	a := make([]byte, outCmdBuf.Len())
-	copy(a, outCmdBuf.Bytes())
-	return a, nil
+	return outCmdBuf.Bytes(), nil
 }
 
 var (