buffer writes when sending protobufs

The protobuf writer performs multiple small writes when writing a
message. We need to buffer these, otherwise we'll send out a packet for
each Write call.

dht_net.go

@@ -1,6 +1,7 @@
 package dht
 
 import (
+	"bufio"
 	"context"
 	"fmt"
 	"io"
@@ -157,10 +158,35 @@ func (dht *IpfsDHT) messageSenderForPeer(p peer.ID) (*messageSender, error) {
 	return ms, nil
 }
 
+type bufferedWriteCloser interface {
+	ggio.WriteCloser
+	Flush() error
+}
+
+// The Protobuf writer performs multiple small writes when writing a message.
+// We need to buffer those writes, to make sure that we're not sending a new
+// packet for every single write.
+type bufferedDelimitedWriter struct {
+	*bufio.Writer
+	ggio.WriteCloser
+}
+
+func newBufferedDelimitedWriter(str inet.Stream) bufferedWriteCloser {
+	w := bufio.NewWriterSize(str, 1000)
+	return &bufferedDelimitedWriter{
+		Writer:      w,
+		WriteCloser: ggio.NewDelimitedWriter(w),
+	}
+}
+
+func (w *bufferedDelimitedWriter) Flush() error {
+	return w.Writer.Flush()
+}
+
 type messageSender struct {
 	s   inet.Stream
 	r   ggio.ReadCloser
-	w   ggio.WriteCloser
+	w   bufferedWriteCloser
 	lk  sync.Mutex
 	p   peer.ID
 	dht *IpfsDHT
@@ -204,7 +230,7 @@ func (ms *messageSender) prep() error {
 	}
 
 	ms.r = ggio.NewDelimitedReader(nstr, inet.MessageSizeMax)
-	ms.w = ggio.NewDelimitedWriter(nstr)
+	ms.w = newBufferedDelimitedWriter(nstr)
 	ms.s = nstr
 
 	return nil
@@ -224,7 +250,7 @@ func (ms *messageSender) SendMessage(ctx context.Context, pmes *pb.Message) erro
 			return err
 		}
 
-		if err := ms.w.WriteMsg(pmes); err != nil {
+		if err := ms.writeMsg(pmes); err != nil {
 			ms.s.Reset()
 			ms.s = nil
 
@@ -260,7 +286,7 @@ func (ms *messageSender) SendRequest(ctx context.Context, pmes *pb.Message) (*pb
 			return nil, err
 		}
 
-		if err := ms.w.WriteMsg(pmes); err != nil {
+		if err := ms.writeMsg(pmes); err != nil {
 			ms.s.Reset()
 			ms.s = nil
 
@@ -302,6 +328,13 @@ func (ms *messageSender) SendRequest(ctx context.Context, pmes *pb.Message) (*pb
 	}
 }
 
+func (ms *messageSender) writeMsg(pmes *pb.Message) error {
+	if err := ms.w.WriteMsg(pmes); err != nil {
+		return err
+	}
+	return ms.w.Flush()
+}
+
 func (ms *messageSender) ctxReadMsg(ctx context.Context, mes *pb.Message) error {
 	errc := make(chan error, 1)
 	go func(r ggio.ReadCloser) {