fix(server): limit implicit large group subscription meta

server/topic.go

@@ -202,6 +202,8 @@ const (
 	StopRehashing
 )
 
+const implicitGroupSubSelfOnlyThreshold = 1000
+
 // Topic shutdown
 type shutDown struct {
 	// Channel to report back completion of topic shutdown. Could be nil
@@ -2894,7 +2896,6 @@ func (t *Topic) replyGetDesc(sess *Session, asUid types.Uid, _ bool, opts *MsgGe
 	if t.cat == types.TopicCatGrp {
 		desc.IsChan = t.isChan
 		desc.SubCnt = t.subCnt
-		logs.Info.Println("replyGetDesc: grp topic", t.name, "subs", t.subCnt)
 	}
 
 	if ifUpdated {
@@ -3353,6 +3354,12 @@ func (t *Topic) replyGetSub(sess *Session, asUid types.Uid, authLevel auth.Level
 			// Channel subscribers are using chnXXX topic name rather than grpXXX.
 			topicName = msg.Original
 		}
+		if req = t.limitImplicitLargeGroupSubQuery(req, asUid, msg); req != nil {
+			ifModified = time.Time{}
+			if req.IfModifiedSince != nil {
+				ifModified = *req.IfModifiedSince
+			}
+		}
 		// Include sub.Public.
 		if ifModified.IsZero() {
 			// No cache management. Skip deleted subscriptions.
@@ -3557,6 +3564,21 @@ func (t *Topic) replyGetSub(sess *Session, asUid types.Uid, authLevel auth.Level
 	return nil
 }
 
+func (t *Topic) limitImplicitLargeGroupSubQuery(req *MsgGetOpts, asUid types.Uid, msg *ClientComMessage) *MsgGetOpts {
+	if t.cat != types.TopicCatGrp || msg == nil || msg.Sub == nil || t.subCnt < implicitGroupSubSelfOnlyThreshold {
+		return req
+	}
+	if req != nil && (req.User != "" || req.Topic != "" || req.Limit != 0 || req.IfModifiedSince != nil) {
+		return req
+	}
+	limited := &MsgGetOpts{}
+	if req != nil {
+		*limited = *req
+	}
+	limited.User = asUid.UserId()
+	return limited
+}
+
 // replySetSub is a response to new subscription request or an update to a subscription {set.sub}:
 // update topic metadata cache, save/update subs, reply to the caller as {ctrl} message,
 // generate a presence notification, if appropriate.