peer+server: use server-wide writeBufferPool for peer write buffers

peer.go

@@ -198,7 +198,7 @@ type peer struct {
 	// messages to write out directly on the socket. By re-using this
 	// buffer, we avoid needing to allocate more memory each time a new
 	// message is to be sent to a peer.
-	writeBuf [lnwire.MaxMessagePayload]byte
+	writeBuf *lnpeer.WriteBuffer
 
 	queueQuit chan struct{}
 	quit      chan struct{}
@@ -239,6 +239,8 @@ func newPeer(conn net.Conn, connReq *connmgr.ConnReq, server *server,
 		chanCloseMsgs:      make(chan *closeMsg),
 		failedChannels:     make(map[lnwire.ChannelID]struct{}),
 
+		writeBuf: server.writeBufferPool.Take(),
+
 		queueQuit: make(chan struct{}),
 		quit:      make(chan struct{}),
 	}
@@ -613,6 +615,11 @@ func (p *peer) WaitForDisconnect(ready chan struct{}) {
 	}
 
 	p.wg.Wait()
+
+	// Now that we are certain all active goroutines which could have been
+	// modifying the write buffer have exited, return the buffer to the pool
+	// to be reused.
+	p.server.writeBufferPool.Return(p.writeBuf)
 }
 
 // Disconnect terminates the connection with the remote peer. Additionally, a

server.go

@@ -165,6 +165,8 @@ type server struct {
 
 	sigPool *lnwallet.SigPool
 
+	writeBufferPool *lnpeer.WriteBufferPool
+
 	// globalFeatures feature vector which affects HTLCs and thus are also
 	// advertised to other nodes.
 	globalFeatures *lnwire.FeatureVector
@@ -260,11 +262,15 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB, cc *chainControl,
 	sharedSecretPath := filepath.Join(graphDir, "sphinxreplay.db")
 	replayLog := htlcswitch.NewDecayedLog(sharedSecretPath, cc.chainNotifier)
 	sphinxRouter := sphinx.NewRouter(privKey, activeNetParams.Params, replayLog)
+	writeBufferPool := lnpeer.NewWriteBufferPool(
+		lnpeer.DefaultGCInterval, lnpeer.DefaultExpiryInterval,
+	)
 
 	s := &server{
 		chanDB:          chanDB,
 		cc:              cc,
 		sigPool:         lnwallet.NewSigPool(runtime.NumCPU()*2, cc.signer),
+		writeBufferPool: writeBufferPool,
 
 		invoices: invoices.NewRegistry(chanDB, activeNetParams.Params),