peer: add SendMessageLazy

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