peer: add SendMessageLazy

discovery/mock_test.go

@@ -35,6 +35,11 @@ func (p *mockPeer) SendMessage(_ bool, msgs ...lnwire.Message) error {
 
 	return nil
 }
+
+func (p *mockPeer) SendMessageLazy(sync bool, msgs ...lnwire.Message) error {
+	return p.SendMessage(sync, msgs...)
+}
+
 func (p *mockPeer) AddNewChannel(_ *channeldb.OpenChannel, _ <-chan struct{}) error {
 	return nil
 }

fundingmanager_test.go

@@ -170,6 +170,10 @@ func (n *testNode) SendMessage(_ bool, msg ...lnwire.Message) error {
 	return n.sendMessage(msg[0])
 }
 
+func (n *testNode) SendMessageLazy(sync bool, msgs ...lnwire.Message) error {
+	return n.SendMessage(sync, msgs...)
+}
+
 func (n *testNode) WipeChannel(_ *wire.OutPoint) error {
 	return nil
 }

htlcswitch/link_test.go

@@ -1549,6 +1549,9 @@ func (m *mockPeer) SendMessage(sync bool, msgs ...lnwire.Message) error {
 	}
 	return nil
 }
+func (m *mockPeer) SendMessageLazy(sync bool, msgs ...lnwire.Message) error {
+	return m.SendMessage(sync, msgs...)
+}
 func (m *mockPeer) AddNewChannel(_ *channeldb.OpenChannel,
 	_ <-chan struct{}) error {
 	return nil

htlcswitch/mock.go

@@ -502,6 +502,10 @@ func (s *mockServer) SendMessage(sync bool, msgs ...lnwire.Message) error {
 	return nil
 }
 
+func (s *mockServer) SendMessageLazy(sync bool, msgs ...lnwire.Message) error {
+	panic("not implemented")
+}
+
 func (s *mockServer) readHandler(message lnwire.Message) error {
 	var targetChan lnwire.ChannelID
 

lnpeer/peer.go

@@ -12,10 +12,17 @@ import (
 // Peer is an interface which represents the remote lightning node inside our
 // system.
 type Peer interface {
-	// SendMessage sends a variadic number of message to remote peer. The
-	// first argument denotes if the method should block until the message
-	// has been sent to the remote peer.
-	SendMessage(sync bool, msg ...lnwire.Message) error
+	// SendMessage sends a variadic number of high-priority message to
+	// remote peer.  The first argument denotes if the method should block
+	// until the messages have been sent to the remote peer or an error is
+	// returned, otherwise it returns immediately after queuing.
+	SendMessage(sync bool, msgs ...lnwire.Message) error
+
+	// SendMessageLazy sends a variadic number of low-priority message to
+	// remote peer. The first argument denotes if the method should block
+	// until the messages have been sent to the remote peer or an error is
+	// returned, otherwise it returns immediately after queueing.
+	SendMessageLazy(sync bool, msgs ...lnwire.Message) error
 
 	// AddNewChannel adds a new channel to the peer. The channel should fail
 	// to be added if the cancel channel is closed.

peer.go

@@ -2351,12 +2351,31 @@ func (p *peer) resendChanSyncMsg(cid lnwire.ChannelID) error {
 	return nil
 }
 
-// SendMessage sends a variadic number of message to remote peer. The first
-// argument denotes if the method should block until the message has been sent
-// to the remote peer.
+// SendMessage sends a variadic number of high-priority message to remote peer.
+// The first argument denotes if the method should block until the messages have
+// been sent to the remote peer or an error is returned, otherwise it returns
+// immediately after queuing.
 //
 // NOTE: Part of the lnpeer.Peer interface.
 func (p *peer) SendMessage(sync bool, msgs ...lnwire.Message) error {
+	return p.sendMessage(sync, true, msgs...)
+}
+
+// SendMessageLazy sends a variadic number of low-priority message to remote
+// peer. The first argument denotes if the method should block until the
+// messages have been sent to the remote peer or an error is returned, otherwise
+// it returns immediately after queueing.
+//
+// NOTE: Part of the lnpeer.Peer interface.
+func (p *peer) SendMessageLazy(sync bool, msgs ...lnwire.Message) error {
+	return p.sendMessage(sync, false, msgs...)
+}
+
+// sendMessage queues a variadic number of messages using the passed priority
+// to the remote peer. If sync is true, this method will block until the
+// messages have been sent to the remote peer or an error is returned, otherwise
+// it returns immediately after queueing.
+func (p *peer) sendMessage(sync, priority bool, msgs ...lnwire.Message) error {
 	// Add all incoming messages to the outgoing queue. A list of error
 	// chans is populated for each message if the caller requested a sync
 	// send.
@@ -2370,7 +2389,11 @@ func (p *peer) SendMessage(sync bool, msgs ...lnwire.Message) error {
 			errChans = append(errChans, errChan)
 		}
 
-		p.queueMsg(msg, errChan)
+		if priority {
+			p.queueMsg(msg, errChan)
+		} else {
+			p.queueMsgLazy(msg, errChan)
+		}
 	}
 
 	// Wait for all replies from the writeHandler. For async sends, this