Packet encoding optimization (#343)

* Dynamically allocate buffer for writes if needed

* Remove unused net.Buffer

* Return bytes written to buffer instead of conn

* Dynamic write buffer

* Reduce double write of pk.Payload

* Use memory pool for packet encode

* Pool doesn't guarantee value between Put and Get

* Add benchmark for bufpool

* Fix issue #346

* Change default pool not to have size cap

---------

Co-authored-by: JB <28275108+mochi-co@users.noreply.github.com>

mempool/bufpool.go

@@ -0,0 +1,81 @@
+package mempool
+
+import (
+	"bytes"
+	"sync"
+)
+
+var bufPool = NewBuffer(0)
+
+// GetBuffer takes a Buffer from the default buffer pool
+func GetBuffer() *bytes.Buffer { return bufPool.Get() }
+
+// PutBuffer returns Buffer to the default buffer pool
+func PutBuffer(x *bytes.Buffer) { bufPool.Put(x) }
+
+type BufferPool interface {
+	Get() *bytes.Buffer
+	Put(x *bytes.Buffer)
+}
+
+// NewBuffer returns a buffer pool. The max specify the max capacity of the Buffer the pool will
+// return. If the Buffer becoomes large than max, it will no longer be returned to the pool. If
+// max <= 0, no limit will be enforced.
+func NewBuffer(max int) BufferPool {
+	if max > 0 {
+		return newBufferWithCap(max)
+	}
+
+	return newBuffer()
+}
+
+// Buffer is a Buffer pool.
+type Buffer struct {
+	pool *sync.Pool
+}
+
+func newBuffer() *Buffer {
+	return &Buffer{
+		pool: &sync.Pool{
+			New: func() any { return new(bytes.Buffer) },
+		},
+	}
+}
+
+// Get a Buffer from the pool.
+func (b *Buffer) Get() *bytes.Buffer {
+	return b.pool.Get().(*bytes.Buffer)
+}
+
+// Put the Buffer back into pool. It resets the Buffer for reuse.
+func (b *Buffer) Put(x *bytes.Buffer) {
+	x.Reset()
+	b.pool.Put(x)
+}
+
+// BufferWithCap is a Buffer pool that
+type BufferWithCap struct {
+	bp  *Buffer
+	max int
+}
+
+func newBufferWithCap(max int) *BufferWithCap {
+	return &BufferWithCap{
+		bp:  newBuffer(),
+		max: max,
+	}
+}
+
+// Get a Buffer from the pool.
+func (b *BufferWithCap) Get() *bytes.Buffer {
+	return b.bp.Get()
+}
+
+// Put the Buffer back into the pool if the capacity doesn't exceed the limit. It resets the Buffer
+// for reuse.
+func (b *BufferWithCap) Put(x *bytes.Buffer) {
+	if x.Cap() > b.max {
+		return
+	}
+	b.bp.Put(x)
+}

mempool/bufpool_test.go

@@ -0,0 +1,96 @@
+package mempool
+
+import (
+	"bytes"
+	"reflect"
+	"runtime/debug"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewBuffer(t *testing.T) {
+	defer debug.SetGCPercent(debug.SetGCPercent(-1))
+	bp := NewBuffer(1000)
+	require.Equal(t, "*mempool.BufferWithCap", reflect.TypeOf(bp).String())
+
+	bp = NewBuffer(0)
+	require.Equal(t, "*mempool.Buffer", reflect.TypeOf(bp).String())
+
+	bp = NewBuffer(-1)
+	require.Equal(t, "*mempool.Buffer", reflect.TypeOf(bp).String())
+}
+
+func TestBuffer(t *testing.T) {
+	defer debug.SetGCPercent(debug.SetGCPercent(-1))
+	Size := 101
+
+	bp := NewBuffer(0)
+	buf := bp.Get()
+
+	for i := 0; i < Size; i++ {
+		buf.WriteByte('a')
+	}
+
+	bp.Put(buf)
+	buf = bp.Get()
+	require.Equal(t, 0, buf.Len())
+}
+
+func TestBufferWithCap(t *testing.T) {
+	defer debug.SetGCPercent(debug.SetGCPercent(-1))
+	Size := 101
+	bp := NewBuffer(100)
+	buf := bp.Get()
+
+	for i := 0; i < Size; i++ {
+		buf.WriteByte('a')
+	}
+
+	bp.Put(buf)
+	buf = bp.Get()
+	require.Equal(t, 0, buf.Len())
+	require.Equal(t, 0, buf.Cap())
+}
+
+func BenchmarkBufferPool(b *testing.B) {
+	bp := NewBuffer(0)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		b := bp.Get()
+		b.WriteString("this is a test")
+		bp.Put(b)
+	}
+}
+
+func BenchmarkBufferPoolWithCapLarger(b *testing.B) {
+	bp := NewBuffer(64 * 1024)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		b := bp.Get()
+		b.WriteString("this is a test")
+		bp.Put(b)
+	}
+}
+
+func BenchmarkBufferPoolWithCapLesser(b *testing.B) {
+	bp := NewBuffer(10)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		b := bp.Get()
+		b.WriteString("this is a test")
+		bp.Put(b)
+	}
+}
+
+func BenchmarkBufferWithoutPool(b *testing.B) {
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		b := new(bytes.Buffer)
+		b.WriteString("this is a test")
+		_ = b
+	}
+}

packets/packets.go

@@ -12,6 +12,8 @@ import (
 	"strconv"
 	"strings"
 	"sync"
+
+	"github.com/mochi-mqtt/server/v2/mempool"
 )
 
 // All valid packet types and their packet identifiers.
@@ -298,7 +300,8 @@ func (s *Subscription) decode(b byte) {
 
 // ConnectEncode encodes a connect packet.
 func (pk *Packet) ConnectEncode(buf *bytes.Buffer) error {
-	nb := bytes.NewBuffer([]byte{})
+	nb := mempool.GetBuffer()
+	defer mempool.PutBuffer(nb)
 	nb.Write(encodeBytes(pk.Connect.ProtocolName))
 	nb.WriteByte(pk.ProtocolVersion)
 
@@ -315,7 +318,8 @@ func (pk *Packet) ConnectEncode(buf *bytes.Buffer) error {
 	nb.Write(encodeUint16(pk.Connect.Keepalive))
 
 	if pk.ProtocolVersion == 5 {
-		pb := bytes.NewBuffer([]byte{})
+		pb := mempool.GetBuffer()
+		defer mempool.PutBuffer(pb)
 		(&pk.Properties).Encode(pk.FixedHeader.Type, pk.Mods, pb, 0)
 		nb.Write(pb.Bytes())
 	}
@@ -324,7 +328,8 @@ func (pk *Packet) ConnectEncode(buf *bytes.Buffer) error {
 
 	if pk.Connect.WillFlag {
 		if pk.ProtocolVersion == 5 {
-			pb := bytes.NewBuffer([]byte{})
+			pb := mempool.GetBuffer()
+			defer mempool.PutBuffer(pb)
 			(&pk.Connect).WillProperties.Encode(WillProperties, pk.Mods, pb, 0)
 			nb.Write(pb.Bytes())
 		}
@@ -493,12 +498,14 @@ func (pk *Packet) ConnectValidate() Code {
 
 // ConnackEncode encodes a Connack packet.
 func (pk *Packet) ConnackEncode(buf *bytes.Buffer) error {
-	nb := bytes.NewBuffer([]byte{})
+	nb := mempool.GetBuffer()
+	defer mempool.PutBuffer(nb)
 	nb.WriteByte(encodeBool(pk.SessionPresent))
 	nb.WriteByte(pk.ReasonCode)
 
 	if pk.ProtocolVersion == 5 {
-		pb := bytes.NewBuffer([]byte{})
+		pb := mempool.GetBuffer()
+		defer mempool.PutBuffer(pb)
 		pk.Properties.Encode(pk.FixedHeader.Type, pk.Mods, pb, nb.Len()+2) // +SessionPresent +ReasonCode
 		nb.Write(pb.Bytes())
 	}
@@ -536,12 +543,14 @@ func (pk *Packet) ConnackDecode(buf []byte) error {
 
 // DisconnectEncode encodes a Disconnect packet.
 func (pk *Packet) DisconnectEncode(buf *bytes.Buffer) error {
-	nb := bytes.NewBuffer([]byte{})
+	nb := mempool.GetBuffer()
+	defer mempool.PutBuffer(nb)
 
 	if pk.ProtocolVersion == 5 {
 		nb.WriteByte(pk.ReasonCode)
 
-		pb := bytes.NewBuffer([]byte{})
+		pb := mempool.GetBuffer()
+		defer mempool.PutBuffer(pb)
 		pk.Properties.Encode(pk.FixedHeader.Type, pk.Mods, pb, nb.Len())
 		nb.Write(pb.Bytes())
 	}
@@ -598,7 +607,8 @@ func (pk *Packet) PingrespDecode(buf []byte) error {
 
 // PublishEncode encodes a Publish packet.
 func (pk *Packet) PublishEncode(buf *bytes.Buffer) error {
-	nb := bytes.NewBuffer([]byte{})
+	nb := mempool.GetBuffer()
+	defer mempool.PutBuffer(nb)
 
 	nb.Write(encodeString(pk.TopicName)) // [MQTT-3.3.2-1]
 
@@ -610,16 +620,16 @@ func (pk *Packet) PublishEncode(buf *bytes.Buffer) error {
 	}
 
 	if pk.ProtocolVersion == 5 {
-		pb := bytes.NewBuffer([]byte{})
+		pb := mempool.GetBuffer()
+		defer mempool.PutBuffer(pb)
 		pk.Properties.Encode(pk.FixedHeader.Type, pk.Mods, pb, nb.Len()+len(pk.Payload))
 		nb.Write(pb.Bytes())
 	}
 
-	nb.Write(pk.Payload)
+	pk.FixedHeader.Remaining = nb.Len() + len(pk.Payload)
-
-	pk.FixedHeader.Remaining = nb.Len()
 	pk.FixedHeader.Encode(buf)
 	_, _ = nb.WriteTo(buf)
+	buf.Write(pk.Payload)
 
 	return nil
 }
@@ -690,11 +700,13 @@ func (pk *Packet) PublishValidate(topicAliasMaximum uint16) Code {
 
 // encodePubAckRelRecComp encodes a Puback, Pubrel, Pubrec, or Pubcomp packet.
 func (pk *Packet) encodePubAckRelRecComp(buf *bytes.Buffer) error {
-	nb := bytes.NewBuffer([]byte{})
+	nb := mempool.GetBuffer()
+	defer mempool.PutBuffer(nb)
 	nb.Write(encodeUint16(pk.PacketID))
 
 	if pk.ProtocolVersion == 5 {
-		pb := bytes.NewBuffer([]byte{})
+		pb := mempool.GetBuffer()
+		defer mempool.PutBuffer(pb)
 		pk.Properties.Encode(pk.FixedHeader.Type, pk.Mods, pb, nb.Len())
 		if pk.ReasonCode >= ErrUnspecifiedError.Code || pb.Len() > 1 {
 			nb.WriteByte(pk.ReasonCode)
@@ -831,11 +843,13 @@ func (pk *Packet) ReasonCodeValid() bool {
 
 // SubackEncode encodes a Suback packet.
 func (pk *Packet) SubackEncode(buf *bytes.Buffer) error {
-	nb := bytes.NewBuffer([]byte{})
+	nb := mempool.GetBuffer()
+	defer mempool.PutBuffer(nb)
 	nb.Write(encodeUint16(pk.PacketID))
 
 	if pk.ProtocolVersion == 5 {
-		pb := bytes.NewBuffer([]byte{})
+		pb := mempool.GetBuffer()
+		defer mempool.PutBuffer(pb)
 		pk.Properties.Encode(pk.FixedHeader.Type, pk.Mods, pb, nb.Len()+len(pk.ReasonCodes))
 		nb.Write(pb.Bytes())
 	}
@@ -878,10 +892,12 @@ func (pk *Packet) SubscribeEncode(buf *bytes.Buffer) error {
 		return ErrProtocolViolationNoPacketID
 	}
 
-	nb := bytes.NewBuffer([]byte{})
+	nb := mempool.GetBuffer()
+	defer mempool.PutBuffer(nb)
 	nb.Write(encodeUint16(pk.PacketID))
 
-	xb := bytes.NewBuffer([]byte{}) // capture and write filters after length checks
+	xb := mempool.GetBuffer() // capture and write filters after length checks
+	defer mempool.PutBuffer(xb)
 	for _, opts := range pk.Filters {
 		xb.Write(encodeString(opts.Filter)) // [MQTT-3.8.3-1]
 		if pk.ProtocolVersion == 5 {
@@ -892,7 +908,8 @@ func (pk *Packet) SubscribeEncode(buf *bytes.Buffer) error {
 	}
 
 	if pk.ProtocolVersion == 5 {
-		pb := bytes.NewBuffer([]byte{})
+		pb := mempool.GetBuffer()
+		defer mempool.PutBuffer(pb)
 		pk.Properties.Encode(pk.FixedHeader.Type, pk.Mods, pb, nb.Len()+xb.Len())
 		nb.Write(pb.Bytes())
 	}
@@ -983,11 +1000,13 @@ func (pk *Packet) SubscribeValidate() Code {
 
 // UnsubackEncode encodes an Unsuback packet.
 func (pk *Packet) UnsubackEncode(buf *bytes.Buffer) error {
-	nb := bytes.NewBuffer([]byte{})
+	nb := mempool.GetBuffer()
+	defer mempool.PutBuffer(nb)
 	nb.Write(encodeUint16(pk.PacketID))
 
 	if pk.ProtocolVersion == 5 {
-		pb := bytes.NewBuffer([]byte{})
+		pb := mempool.GetBuffer()
+		defer mempool.PutBuffer(pb)
 		pk.Properties.Encode(pk.FixedHeader.Type, pk.Mods, pb, nb.Len())
 		nb.Write(pb.Bytes())
 	}
@@ -1031,16 +1050,19 @@ func (pk *Packet) UnsubscribeEncode(buf *bytes.Buffer) error {
 		return ErrProtocolViolationNoPacketID
 	}
 
-	nb := bytes.NewBuffer([]byte{})
+	nb := mempool.GetBuffer()
+	defer mempool.PutBuffer(nb)
 	nb.Write(encodeUint16(pk.PacketID))
 
-	xb := bytes.NewBuffer([]byte{}) // capture filters and write after length checks
+	xb := mempool.GetBuffer() // capture filters and write after length checks
+	defer mempool.PutBuffer(xb)
 	for _, sub := range pk.Filters {
 		xb.Write(encodeString(sub.Filter)) // [MQTT-3.10.3-1]
 	}
 
 	if pk.ProtocolVersion == 5 {
-		pb := bytes.NewBuffer([]byte{})
+		pb := mempool.GetBuffer()
+		defer mempool.PutBuffer(pb)
 		pk.Properties.Encode(pk.FixedHeader.Type, pk.Mods, pb, nb.Len()+xb.Len())
 		nb.Write(pb.Bytes())
 	}
@@ -1100,10 +1122,12 @@ func (pk *Packet) UnsubscribeValidate() Code {
 
 // AuthEncode encodes an Auth packet.
 func (pk *Packet) AuthEncode(buf *bytes.Buffer) error {
-	nb := bytes.NewBuffer([]byte{})
+	nb := mempool.GetBuffer()
+	defer mempool.PutBuffer(nb)
 	nb.WriteByte(pk.ReasonCode)
 
-	pb := bytes.NewBuffer([]byte{})
+	pb := mempool.GetBuffer()
+	defer mempool.PutBuffer(pb)
 	pk.Properties.Encode(pk.FixedHeader.Type, pk.Mods, pb, nb.Len())
 	nb.Write(pb.Bytes())