Merge pull request #2045 from OffchainLabs/always-broadcast-feed

Always broadcast feed, even when the node isn't the sequencer

arbnode/seq_coordinator.go

@@ -650,6 +650,8 @@ func (c *SeqCoordinator) update(ctx context.Context) time.Duration {
 					log.Warn("failed sequencing delayed messages after catching lock", "err", err)
 				}
 			}
+			// This should be redundant now that even non-primary sequencers broadcast over the feed,
+			// but the backlog efficiently deduplicates messages, so better safe than sorry.
 			err = c.streamer.PopulateFeedBacklog()
 			if err != nil {
 				log.Warn("failed to populate the feed backlog on lockout acquisition", "err", err)

arbnode/transaction_streamer.go

@@ -862,12 +862,6 @@ func (s *TransactionStreamer) WriteMessageFromSequencer(pos arbutil.MessageIndex
 		return err
 	}
 
-	if s.broadcastServer != nil {
-		if err := s.broadcastServer.BroadcastSingle(msgWithMeta, pos); err != nil {
-			log.Error("failed broadcasting message", "pos", pos, "err", err)
-		}
-	}
-
 	return nil
 }
 
@@ -927,6 +921,12 @@ func (s *TransactionStreamer) writeMessages(pos arbutil.MessageIndex, messages [
 	default:
 	}
 
+	if s.broadcastServer != nil {
+		if err := s.broadcastServer.BroadcastMessages(messages, pos); err != nil {
+			log.Error("failed broadcasting message", "pos", pos, "err", err)
+		}
+	}
+
 	return nil
 }
 

broadcaster/backlog/backlog.go

@@ -379,7 +379,7 @@ func (s *backlogSegment) Contains(i uint64) bool {
 	s.messagesLock.RLock()
 	defer s.messagesLock.RUnlock()
 	start := s.start()
-	if i < start || i > s.end() {
+	if i < start || i > s.end() || len(s.messages) == 0 {
 		return false
 	}
 

broadcaster/broadcaster.go

@@ -5,6 +5,7 @@ package broadcaster
 
 import (
 	"context"
+	"errors"
 	"net"
 
 	"github.com/gobwas/ws"
@@ -56,10 +57,11 @@ func (b *Broadcaster) NewBroadcastFeedMessage(message arbostypes.MessageWithMeta
 	}, nil
 }
 
-func (b *Broadcaster) BroadcastSingle(msg arbostypes.MessageWithMetadata, seq arbutil.MessageIndex) error {
+func (b *Broadcaster) BroadcastSingle(msg arbostypes.MessageWithMetadata, seq arbutil.MessageIndex) (err error) {
 	defer func() {
 		if r := recover(); r != nil {
 			log.Error("recovered error in BroadcastSingle", "recover", r)
+			err = errors.New("panic in BroadcastSingle")
 		}
 	}()
 	bfm, err := b.NewBroadcastFeedMessage(msg, seq)
@@ -79,6 +81,27 @@ func (b *Broadcaster) BroadcastSingleFeedMessage(bfm *m.BroadcastFeedMessage) {
 	b.BroadcastFeedMessages(broadcastFeedMessages)
 }
 
+func (b *Broadcaster) BroadcastMessages(messages []arbostypes.MessageWithMetadata, seq arbutil.MessageIndex) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			log.Error("recovered error in BroadcastMessages", "recover", r)
+			err = errors.New("panic in BroadcastMessages")
+		}
+	}()
+	var feedMessages []*m.BroadcastFeedMessage
+	for _, msg := range messages {
+		bfm, err := b.NewBroadcastFeedMessage(msg, seq)
+		if err != nil {
+			return err
+		}
+		feedMessages = append(feedMessages, bfm)
+	}
+
+	b.BroadcastFeedMessages(feedMessages)
+
+	return nil
+}
+
 func (b *Broadcaster) BroadcastFeedMessages(messages []*m.BroadcastFeedMessage) {
 
 	bm := &m.BroadcastMessage{

wsbroadcastserver/clientconnection.go

@@ -119,6 +119,7 @@ func (cc *ClientConnection) Remove() {
 
 func (cc *ClientConnection) writeBacklog(ctx context.Context, segment backlog.BacklogSegment) error {
 	var prevSegment backlog.BacklogSegment
+	isFirstSegment := true
 	for !backlog.IsBacklogSegmentNil(segment) {
 		// must get the next segment before the messages to be sent are
 		// retrieved ensures another segment is not added in between calls.
@@ -132,10 +133,14 @@ func (cc *ClientConnection) writeBacklog(ctx context.Context, segment backlog.Ba
 		}
 
 		msgs := prevSegment.Messages()
-		if prevSegment.Contains(uint64(cc.requestedSeqNum)) {
+		if isFirstSegment && prevSegment.Contains(uint64(cc.requestedSeqNum)) {
 			requestedIdx := int(cc.requestedSeqNum) - int(prevSegment.Start())
-			msgs = msgs[requestedIdx:]
+			// This might be false if messages were added after we fetched the segment's messages
+			if len(msgs) >= requestedIdx {
+				msgs = msgs[requestedIdx:]
+			}
 		}
+		isFirstSegment = false
 		bm := &m.BroadcastMessage{
 			Version:  m.V1,
 			Messages: msgs,