Add initial backfilling on portal creation

backfill.go

@@ -16,6 +16,29 @@ import (
 	"go.mau.fi/mautrix-discord/database"
 )
 
+func (portal *Portal) forwardBackfillInitial(source *User) {
+	defer portal.forwardBackfillLock.Unlock()
+	// This should only be called from CreateMatrixRoom which locks forwardBackfillLock before creating the room.
+	if portal.forwardBackfillLock.TryLock() {
+		panic("forwardBackfillInitial() called without locking forwardBackfillLock")
+	}
+
+	limit := portal.bridge.Config.Bridge.Backfill.Limits.Initial.Channel
+	if portal.GuildID == "" {
+		limit = portal.bridge.Config.Bridge.Backfill.Limits.Initial.DM
+	}
+	if limit == 0 {
+		return
+	}
+
+	log := portal.zlog.With().
+		Str("action", "initial backfill").
+		Int("limit", limit).
+		Logger()
+
+	portal.backfillLimited(log, source, limit, "")
+}
+
 func (portal *Portal) ForwardBackfillMissed(source *User, meta *discordgo.Channel) {
 	limit := portal.bridge.Config.Bridge.Backfill.Limits.Missed.Channel
 	if portal.GuildID == "" {
@@ -50,7 +73,7 @@ func (portal *Portal) ForwardBackfillMissed(source *User, meta *discordgo.Channe
 	if limit < 0 {
 		portal.backfillUnlimitedMissed(log, source, lastMessage.DiscordID)
 	} else {
-		portal.backfillLimitedMissed(log, source, limit, lastMessage.DiscordID)
+		portal.backfillLimited(log, source, limit, lastMessage.DiscordID)
 	}
 }
 
@@ -66,6 +89,7 @@ func (portal *Portal) collectBackfillMessages(log zerolog.Logger, source *User,
 		if err != nil {
 			return nil, false, err
 		}
+		if until != "" {
 			for i, msg := range newMessages {
 				if compareMessageIDs(msg.ID, until) <= 0 {
 					log.Debug().
@@ -77,6 +101,7 @@ func (portal *Portal) collectBackfillMessages(log zerolog.Logger, source *User,
 					break
 				}
 			}
+		}
 		messages = append(messages, newMessages...)
 		log.Debug().Int("count", len(newMessages)).Msg("Added messages to backfill collection")
 		if len(newMessages) <= messageFetchChunkSize || len(messages) >= limit {
@@ -90,7 +115,7 @@ func (portal *Portal) collectBackfillMessages(log zerolog.Logger, source *User,
 	return messages, foundAll, nil
 }
 
-func (portal *Portal) backfillLimitedMissed(log zerolog.Logger, source *User, limit int, after string) {
+func (portal *Portal) backfillLimited(log zerolog.Logger, source *User, limit int, after string) {
 	messages, foundAll, err := portal.collectBackfillMessages(log, source, limit, after)
 	if err != nil {
 		log.Err(err).Msg("Error collecting messages to forward backfill")

example-config.yaml

@@ -189,13 +189,18 @@ bridge:
     backfill:
         # Should backfill be enabled at all?
         enabled: false
-        # Limits for backfilling. Set to 0 to disable that type of backfill, or -1 for unlimited.
+        # Limits for backfilling.
         limits:
-            # Initial backfill (when creating portal).
+            # Initial backfill (when creating portal). 0 means backfill is disabled.
+            # A special unlimited value is not supported, you must set a limit. Initial backfill will
+            # fetch all messages first before backfilling anything, so high limits can take a lot of time.
             initial:
                 dm: 50
                 channel: 0
             # Missed message backfill (on startup).
+            # 0 means backfill is disabled, -1 means fetch all messages since last bridged message.
+            # When using unlimited backfill (-1), messages are backfilled as they are fetched.
+            # With limits, all messages up to the limit are fetched first and backfilled afterwards.
             missed:
                 dm: 50
                 channel: 0

portal.go

@@ -261,13 +261,10 @@ func (portal *Portal) messageLoop() {
 	for {
 		select {
 		case msg := <-portal.matrixMessages:
-			portal.forwardBackfillLock.Lock()
 			portal.handleMatrixMessages(msg)
 		case msg := <-portal.discordMessages:
-			portal.forwardBackfillLock.Lock()
 			portal.handleDiscordMessages(msg)
 		}
-		portal.forwardBackfillLock.Unlock()
 	}
 }
 
@@ -468,6 +465,16 @@ func (portal *Portal) CreateMatrixRoom(user *User, channel *discordgo.Channel) e
 	if !portal.shouldSetDMRoomMetadata() {
 		req.Name = ""
 	}
+
+	var backfillStarted bool
+	portal.forwardBackfillLock.Lock()
+	defer func() {
+		if !backfillStarted {
+			portal.log.Debugln("Backfill wasn't started, unlocking forward backfill lock")
+			portal.forwardBackfillLock.Unlock()
+		}
+	}()
+
 	resp, err := intent.CreateRoom(req)
 	if err != nil {
 		portal.log.Warnln("Failed to create room:", err)
@@ -515,6 +522,9 @@ func (portal *Portal) CreateMatrixRoom(user *User, channel *discordgo.Channel) e
 		portal.Update()
 	}
 
+	go portal.forwardBackfillInitial(user)
+	backfillStarted = true
+
 	return nil
 }
 
@@ -532,6 +542,8 @@ func (portal *Portal) handleDiscordMessages(msg portalDiscordMessage) {
 			return
 		}
 	}
+	portal.forwardBackfillLock.Lock()
+	defer portal.forwardBackfillLock.Unlock()
 
 	switch convertedMsg := msg.msg.(type) {
 	case *discordgo.MessageCreate:
@@ -918,6 +930,8 @@ func (portal *Portal) sendMatrixMessage(intent *appservice.IntentAPI, eventType
 }
 
 func (portal *Portal) handleMatrixMessages(msg portalMatrixMessage) {
+	portal.forwardBackfillLock.Lock()
+	defer portal.forwardBackfillLock.Unlock()
 	switch msg.evt.Type {
 	case event.EventMessage, event.EventSticker:
 		portal.handleMatrixMessage(msg.user, msg.evt)