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hack: make backfill work multiple times
This commit is contained in:
Kegan Dougal
parent
ff90b77a16
commit
3df9983296
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@ -357,54 +357,6 @@ func (r *messagesReq) handleNonEmptyEventsSlice(streamEvents []types.StreamEvent
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return
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}
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// containsBackwardExtremity checks if a slice of StreamEvent contains a
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// backward extremity. It does so by selecting the earliest event in the slice
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// and by checking the presence in the database of all of its parent events, and
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// considers the event itself a backward extremity if at least one of the parent
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// events doesn't exist in the database.
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// Returns an error if there was an issue with talking to the database.
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//
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// This function is unused but currently set to nolint for now until we are
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// absolutely sure that the changes in matrix-org/dendrite#847 are behaving
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// properly.
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// nolint:unused
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func (r *messagesReq) containsBackwardExtremity(events []types.StreamEvent) (bool, error) {
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// Select the earliest retrieved event.
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var ev *types.StreamEvent
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if r.backwardOrdering {
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ev = &(events[len(events)-1])
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} else {
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ev = &(events[0])
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}
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// Get the earliest retrieved event's parents.
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prevIDs := ev.PrevEventIDs()
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prevs, err := r.db.Events(r.ctx, prevIDs)
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if err != nil {
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return false, nil
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}
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// Check if we have all of the events we requested. If not, it means we've
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// reached a backward extremity.
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var eventInDB bool
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var id string
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// Iterate over the IDs we used in the request.
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for _, id = range prevIDs {
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eventInDB = false
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// Iterate over the events we got in response.
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for _, ev := range prevs {
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if ev.EventID() == id {
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eventInDB = true
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}
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}
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// One occurrence of one the event's parents not being present in the
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// database is enough to say that the event is a backward extremity.
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if !eventInDB {
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return true, nil
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}
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}
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return false, nil
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}
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// backfill performs a backfill request over the federation on another
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// homeserver in the room.
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// See: https://matrix.org/docs/spec/server_server/latest#get-matrix-federation-v1-backfill-roomid
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@ -415,31 +367,9 @@ func (r *messagesReq) containsBackwardExtremity(events []types.StreamEvent) (boo
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// Returns an error if there was an issue with retrieving the list of servers in
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// the room or sending the request.
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func (r *messagesReq) backfill(fromEventIDs []string, limit int) ([]gomatrixserverlib.HeaderedEvent, error) {
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// Query the list of servers in the room when one of the backward extremities
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// was sent.
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var serversResponse api.QueryServersInRoomAtEventResponse
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serversRequest := api.QueryServersInRoomAtEventRequest{
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RoomID: r.roomID,
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EventID: fromEventIDs[0],
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}
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if err := r.queryAPI.QueryServersInRoomAtEvent(r.ctx, &serversRequest, &serversResponse); err != nil {
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return nil, err
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}
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// Use the first server from the response, except if that server is us.
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// In that case, use the second one if the roomserver responded with
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// enough servers. If not, use an empty string to prevent the backfill
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// from happening as there's no server to direct the request towards.
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// TODO: Be smarter at selecting the server to direct the request
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// towards.
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srvToBackfillFrom := serversResponse.Servers[0]
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if srvToBackfillFrom == r.cfg.Matrix.ServerName {
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if len(serversResponse.Servers) > 1 {
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srvToBackfillFrom = serversResponse.Servers[1]
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} else {
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util.GetLogger(r.ctx).Info("Not enough servers to backfill from")
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return nil, nil
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}
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srvToBackfillFrom, err := r.serverToBackfillFrom(fromEventIDs)
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if err != nil {
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return nil, fmt.Errorf("Cannot find server to backfill from: %w", err)
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}
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pdus := make([]gomatrixserverlib.HeaderedEvent, 0)
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@ -478,6 +408,62 @@ func (r *messagesReq) backfill(fromEventIDs []string, limit int) ([]gomatrixserv
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return pdus, nil
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}
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func (r *messagesReq) serverToBackfillFrom(fromEventIDs []string) (gomatrixserverlib.ServerName, error) {
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// Query the list of servers in the room when one of the backward extremities
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// was sent.
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var serversResponse api.QueryServersInRoomAtEventResponse
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serversRequest := api.QueryServersInRoomAtEventRequest{
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RoomID: r.roomID,
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EventID: fromEventIDs[0],
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}
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if err := r.queryAPI.QueryServersInRoomAtEvent(r.ctx, &serversRequest, &serversResponse); err != nil {
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util.GetLogger(r.ctx).WithError(err).Warn("Failed to query servers in room at event, falling back to event sender")
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// FIXME: We shouldn't be doing this but in situations where we have already backfilled once
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// the query API doesn't work as backfilled events do not make it to the room server.
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// This means QueryServersInRoomAtEvent returns an error as it doesn't have the event ID in question.
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// We need to inject backfilled events into the room server and store them appropriately.
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events, err := r.db.Events(r.ctx, fromEventIDs)
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if err != nil {
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return "", err
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}
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if len(events) == 0 {
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// should be impossible as these event IDs are backwards extremities
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return "", fmt.Errorf("backfill: missing backwards extremities, event IDs: %s", fromEventIDs)
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}
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// The rationale here is that the last event was unlikely to be sent by us, so poke the server who sent it.
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// We shouldn't be doing this really, but as a heuristic it should work pretty well for now.
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for _, e := range events {
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_, srv, err := gomatrixserverlib.SplitID('@', e.Sender())
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if err != nil {
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util.GetLogger(r.ctx).WithError(err).Warn("Failed to extract domain from event sender")
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continue
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}
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if srv != r.cfg.Matrix.ServerName {
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return srv, nil
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}
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}
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// no valid events which have a remote server, fail.
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return "", err
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}
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// Use the first server from the response, except if that server is us.
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// In that case, use the second one if the roomserver responded with
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// enough servers. If not, use an empty string to prevent the backfill
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// from happening as there's no server to direct the request towards.
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// TODO: Be smarter at selecting the server to direct the request
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// towards.
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srvToBackfillFrom := serversResponse.Servers[0]
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if srvToBackfillFrom == r.cfg.Matrix.ServerName {
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if len(serversResponse.Servers) > 1 {
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srvToBackfillFrom = serversResponse.Servers[1]
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} else {
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util.GetLogger(r.ctx).Info("Not enough servers to backfill from")
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return "", nil
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}
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}
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return srvToBackfillFrom, nil
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}
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// setToDefault returns the default value for the "to" query parameter of a
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// request to /messages if not provided. It defaults to either the earliest
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// topological position (if we're going backward) or to the latest one (if we're
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