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Handle duplicate kafka messages (#301)

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The way we store the partition offsets for kafka streams means that when
we start after a crash we may get the last message we processed again.
This means that we have to be careful to ensure that the processing
handles consecutive duplicates correctly.
This commit is contained in:
Erik Johnston 2017-10-16 13:20:24 +01:00 committed by GitHub
parent 1a026f16d5
commit 35b628f5bf
2 changed files with 27 additions and 8 deletions
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16
src/github.com/matrix-org/dendrite/federationsender/consumers/roomserver.go
View file

@ -134,6 +134,14 @@ func (s *OutputRoomEventConsumer) processMessage(ore api.OutputNewRoomEvent) err
return err
}
if oldJoinedHosts == nil {
// This means that there is nothing to update as this is a duplicate
// message.
// This can happen if dendrite crashed between reading the message and
// persisting the stream position.
return nil
}
if ore.SendAsServer == api.DoNotSendToOtherServers {
// Ignore event that we don't need to send anywhere.
return nil
@ -146,13 +154,9 @@ func (s *OutputRoomEventConsumer) processMessage(ore api.OutputNewRoomEvent) err
}
// Send the event.
if err = s.queues.SendEvent(
return s.queues.SendEvent(
&ore.Event, gomatrixserverlib.ServerName(ore.SendAsServer), joinedHostsAtEvent,
); err != nil {
return err
}
return nil
)
}
// joinedHostsAtEvent works out a list of matrix servers that were joined to

19
src/github.com/matrix-org/dendrite/federationsender/storage/storage.go
View file

@ -62,7 +62,10 @@ func (d *Database) prepare() error {
}
// UpdateRoom updates the joined hosts for a room and returns what the joined
// hosts were before the update.
// hosts were before the update, or nil if this was a duplicate message.
// This is called when we receive a message from kafka, so we pass in
// oldEventID and newEventID to check that we haven't missed any messages or
// this isn't a duplicate message.
func (d *Database) UpdateRoom(
ctx context.Context,
roomID, oldEventID, newEventID string,
@ -70,22 +73,34 @@ func (d *Database) UpdateRoom(
removeHosts []string,
) (joinedHosts []types.JoinedHost, err error) {
err = common.WithTransaction(d.db, func(txn *sql.Tx) error {
if err = d.insertRoom(ctx, txn, roomID); err != nil {
err = d.insertRoom(ctx, txn, roomID)
if err != nil {
return err
}
lastSentEventID, err := d.selectRoomForUpdate(ctx, txn, roomID)
if err != nil {
return err
}
if lastSentEventID == newEventID {
// We've handled this message before, so let's just ignore it.
// We can only get a duplicate for the last message we processed,
// so its enough just to compare the newEventID with lastSentEventID
return nil
}
if lastSentEventID != oldEventID {
return types.EventIDMismatchError{
DatabaseID: lastSentEventID, RoomServerID: oldEventID,
}
}
joinedHosts, err = d.selectJoinedHosts(ctx, txn, roomID)
if err != nil {
return err
}
for _, add := range addHosts {
err = d.insertJoinedHosts(ctx, txn, roomID, add.MemberEventID, add.ServerName)
if err != nil {