Refactor Kafka publishing without DB outbox

server/topic.go

@@ -2984,11 +2984,20 @@ func (t *Topic) replyGetData(sess *Session, asUid types.Uid, asChan bool, req *M
 	count := 0
 	if userData := t.perUser[asUid]; (userData.modeGiven & userData.modeWant).IsReader() {
 		// Read messages from DB
-		messages, err := store.Messages.GetAll(t.tenantID, t.name, asUid, msgOpts2storeOpts(req))
+		opts := msgOpts2storeOpts(req)
+		messages, err := store.Messages.GetAll(t.tenantID, t.name, asUid, opts)
 		if err != nil {
 			sess.queueOut(ErrUnknownReply(msg, now))
 			return err
 		}
+		if len(messages) == 0 && shouldTryHotMessageFallback(t.cat, t.lastID, opts) {
+			hotMessages, ok, cacheErr := store.GetHotMessages(t.tenantID, t.name, opts, hotMessageFallbackLimit(opts))
+			if cacheErr != nil {
+				logs.Warn.Printf("get.data hot message fallback failed topic=%s user=%s: %v", t.name, asUid.UserId(), cacheErr)
+			} else if ok {
+				messages = filterHotMessagesForUser(hotMessages, asUid)
+			}
+		}
 
 		// Push the list of messages to the client as {data}.
 		if messages != nil {
@@ -3032,6 +3041,56 @@ func (t *Topic) replyGetData(sess *Session, asUid types.Uid, asChan bool, req *M
 	return nil
 }
 
+func shouldTryHotMessageFallback(cat types.TopicCat, lastID int64, opts *types.QueryOpt) bool {
+	if cat != types.TopicCatGrp || opts == nil || opts.IfModifiedSince != nil ||
+		!opts.User.IsZero() || opts.Topic != "" || opts.Since <= 0 || opts.Before > 0 || len(opts.IdRanges) > 0 {
+		return false
+	}
+	limit := hotMessageFallbackLimit(opts)
+	if limit <= 0 || limit > 10 {
+		return false
+	}
+	floor := lastID - 10
+	if floor < 1 {
+		floor = 1
+	}
+	return lastID <= 0 || opts.Since >= floor
+}
+
+func hotMessageFallbackLimit(opts *types.QueryOpt) int {
+	if opts != nil && opts.Limit > 0 {
+		return opts.Limit
+	}
+	return 1
+}
+
+func filterHotMessagesForUser(messages []types.Message, asUid types.Uid) []types.Message {
+	if len(messages) == 0 {
+		return messages
+	}
+	filtered := messages[:0]
+	for i := range messages {
+		if hotMessageVisibleToUser(&messages[i], asUid) {
+			filtered = append(filtered, messages[i])
+		}
+	}
+	return filtered
+}
+
+func hotMessageVisibleToUser(msg *types.Message, asUid types.Uid) bool {
+	if msg == nil || msg.DeletedAt != nil || msg.DelId > 0 || asUid.IsZero() {
+		return msg != nil && msg.DeletedAt == nil && msg.DelId == 0
+	}
+	uid := asUid.String()
+	userID := asUid.UserId()
+	for _, deleted := range msg.DeletedFor {
+		if deleted.User == uid || deleted.User == userID {
+			return false
+		}
+	}
+	return true
+}
+
 // replyGetTags returns topics' tags - tokens used for discovery.
 func (t *Topic) replyGetTags(sess *Session, asUid types.Uid, msg *ClientComMessage) error {
 	now := types.TimeNow()