Improved, configurable buffer pools

buffer.go

@@ -2,9 +2,6 @@ package render
 
 import "bytes"
 
-// bufPool represents a reusable buffer pool for executing templates into.
-var bufPool *BufferPool
-
 // BufferPool implements a pool of bytes.Buffers in the form of a bounded channel.
 // Pulled from the github.com/oxtoacart/bpool package (Apache licensed).
 type BufferPool struct {
@@ -39,8 +36,3 @@ func (bp *BufferPool) Put(b *bytes.Buffer) {
 	default: // Discard the buffer if the pool is full.
 	}
 }
-
-// Initialize buffer pool for writing templates into.
-func init() {
-	bufPool = NewBufferPool(64)
-}

engine.go

@@ -30,6 +30,8 @@ type HTML struct {
 	Head
 	Name      string
 	Templates *template.Template
+
+	bp GenericBufferPool
 }
 
 // JSON built-in renderer.
@@ -82,20 +84,23 @@ func (d Data) Render(w io.Writer, v interface{}) error {
 
 // Render a HTML response.
 func (h HTML) Render(w io.Writer, binding interface{}) error {
-	// Retrieve a buffer from the pool to write to.
-	out := bufPool.Get()
-	err := h.Templates.ExecuteTemplate(out, h.Name, binding)
+	var buf *bytes.Buffer
+	if h.bp != nil {
+		// If we have a bufferpool, allocate from it
+		buf = h.bp.Get()
+		defer h.bp.Put(buf)
+	}
+
+	err := h.Templates.ExecuteTemplate(buf, h.Name, binding)
 	if err != nil {
 		return err
 	}
 
 	if hw, ok := w.(http.ResponseWriter); ok {
 		h.Head.Write(hw)
 	}
-	out.WriteTo(w)
+	buf.WriteTo(w)
 
-	// Return the buffer to the pool.
-	bufPool.Put(out)
 	return nil
 }
 

genericbufferpool.go

@@ -0,0 +1,9 @@
+package render
+
+import "bytes"
+
+// GenericBufferPool abstracts buffer pool implementations
+type GenericBufferPool interface {
+	Get() *bytes.Buffer
+	Put(*bytes.Buffer)
+}

render.go

@@ -103,6 +103,10 @@ type Options struct {
 	// Enables using partials without the current filename suffix which allows use of the same template in multiple files. e.g {{ partial "carosuel" }} inside the home template will match carosel-home or carosel.
 	// ***NOTE*** - This option should be named RenderPartialsWithoutSuffix as that is what it does. "Prefix" is a typo. Maintaining the existing name for backwards compatibility.
 	RenderPartialsWithoutPrefix bool
+
+	// BufferPool to use when rendering HTML templates. If none is supplied
+	// defaults to SizedBufferPool of size 32 with 512KiB buffers.
+	BufferPool GenericBufferPool
 }
 
 // HTMLOptions is a struct for overriding some rendering Options for specific HTML call.
@@ -176,6 +180,10 @@ func (r *Render) prepareOptions() {
 	if len(r.opt.XMLContentType) == 0 {
 		r.opt.XMLContentType = ContentXML
 	}
+	if r.opt.BufferPool == nil {
+		// 32 buffers of size 512KiB each
+		r.opt.BufferPool = NewSizedBufferPool(32, 1<<19)
+	}
 }
 
 func (r *Render) compileTemplates() {
@@ -410,6 +418,7 @@ func (r *Render) HTML(w io.Writer, status int, name string, binding interface{},
 		Head:      head,
 		Name:      name,
 		Templates: r.templates,
+		bp:        r.opt.BufferPool,
 	}
 
 	return r.Render(w, h, binding)

render_html_test.go

@@ -1,6 +1,7 @@
 package render
 
 import (
+	"bytes"
 	"errors"
 	"html/template"
 	"net/http"
@@ -67,6 +68,38 @@ func TestHTMLBasic(t *testing.T) {
 	expect(t, res.Body.String(), "<h1>Hello gophers</h1>\n")
 }
 
+func BenchmarkBigHTMLBuffers(b *testing.B) {
+	b.ReportAllocs()
+
+	render := New(Options{
+		Directory: "fixtures/basic",
+	})
+
+	var buf = new(bytes.Buffer)
+	for i := 0; i < b.N; i++ {
+		render.HTML(buf, http.StatusOK, "hello", "gophers")
+		buf.Reset()
+	}
+}
+
+func BenchmarkSmallHTMLBuffers(b *testing.B) {
+	b.ReportAllocs()
+
+	render := New(Options{
+		Directory: "fixtures/basic",
+
+		// Tiny 8 bytes buffers -> should lead to allocations
+		// on every template render
+		BufferPool: NewSizedBufferPool(32, 8),
+	})
+
+	var buf = new(bytes.Buffer)
+	for i := 0; i < b.N; i++ {
+		render.HTML(buf, http.StatusOK, "hello", "gophers")
+		buf.Reset()
+	}
+}
+
 func TestHTMLXHTML(t *testing.T) {
 	render := New(Options{
 		Directory:       "fixtures/basic",

sizedbufferpool.go

@@ -0,0 +1,62 @@
+package render
+
+import (
+	"bytes"
+)
+
+// Pulled from the github.com/oxtoacart/bpool package (Apache licensed).
+
+// SizedBufferPool implements a pool of bytes.Buffers in the form of a bounded
+// channel. Buffers are pre-allocated to the requested size.
+type SizedBufferPool struct {
+	c chan *bytes.Buffer
+	a int
+}
+
+// NewSizedBufferPool creates a new BufferPool bounded to the given size.
+// size defines the number of buffers to be retained in the pool and alloc sets
+// the initial capacity of new buffers to minimize calls to make().
+//
+// The value of alloc should seek to provide a buffer that is representative of
+// most data written to the the buffer (i.e. 95th percentile) without being
+// overly large (which will increase static memory consumption). You may wish to
+// track the capacity of your last N buffers (i.e. using an []int) prior to
+// returning them to the pool as input into calculating a suitable alloc value.
+func NewSizedBufferPool(size int, alloc int) (bp *SizedBufferPool) {
+	return &SizedBufferPool{
+		c: make(chan *bytes.Buffer, size),
+		a: alloc,
+	}
+}
+
+// Get gets a Buffer from the SizedBufferPool, or creates a new one if none are
+// available in the pool. Buffers have a pre-allocated capacity.
+func (bp *SizedBufferPool) Get() (b *bytes.Buffer) {
+	select {
+	case b = <-bp.c:
+		// reuse existing buffer
+	default:
+		// create new buffer
+		b = bytes.NewBuffer(make([]byte, 0, bp.a))
+	}
+	return
+}
+
+// Put returns the given Buffer to the SizedBufferPool.
+func (bp *SizedBufferPool) Put(b *bytes.Buffer) {
+	b.Reset()
+
+	// Release buffers over our maximum capacity and re-create a pre-sized
+	// buffer to replace it.
+	// Note that the cap(b.Bytes()) provides the capacity from the read off-set
+	// only, but as we've called b.Reset() the full capacity of the underlying
+	// byte slice is returned.
+	if cap(b.Bytes()) > bp.a {
+		b = bytes.NewBuffer(make([]byte, 0, bp.a))
+	}
+
+	select {
+	case bp.c <- b:
+	default: // Discard the buffer if the pool is full.
+	}
+}