package perform import ( "context" "fmt" "github.com/matrix-org/dendrite/internal/eventutil" "github.com/matrix-org/dendrite/roomserver/api" "github.com/matrix-org/dendrite/roomserver/auth" "github.com/matrix-org/dendrite/roomserver/internal/helpers" "github.com/matrix-org/dendrite/roomserver/storage" "github.com/matrix-org/dendrite/roomserver/types" "github.com/matrix-org/gomatrixserverlib" "github.com/matrix-org/util" "github.com/sirupsen/logrus" ) type Backfiller struct { ServerName gomatrixserverlib.ServerName DB storage.Database FedClient *gomatrixserverlib.FederationClient KeyRing gomatrixserverlib.JSONVerifier } // PerformBackfill implements api.RoomServerQueryAPI func (r *Backfiller) PerformBackfill( ctx context.Context, request *api.PerformBackfillRequest, response *api.PerformBackfillResponse, ) error { // if we are requesting the backfill then we need to do a federation hit // TODO: we could be more sensible and fetch as many events we already have then request the rest // which is what the syncapi does already. if request.ServerName == r.ServerName { return r.backfillViaFederation(ctx, request, response) } // someone else is requesting the backfill, try to service their request. var err error var front []string // The limit defines the maximum number of events to retrieve, so it also // defines the highest number of elements in the map below. visited := make(map[string]bool, request.Limit) // this will include these events which is what we want front = request.PrevEventIDs() info, err := r.DB.RoomInfo(ctx, request.RoomID) if err != nil { return err } if info == nil || info.IsStub { return fmt.Errorf("PerformBackfill: missing room info for room %s", request.RoomID) } // Scan the event tree for events to send back. resultNIDs, err := helpers.ScanEventTree(ctx, r.DB, *info, front, visited, request.Limit, request.ServerName) if err != nil { return err } // Retrieve events from the list that was filled previously. var loadedEvents []gomatrixserverlib.Event loadedEvents, err = helpers.LoadEvents(ctx, r.DB, resultNIDs) if err != nil { return err } for _, event := range loadedEvents { response.Events = append(response.Events, event.Headered(info.RoomVersion)) } return err } func (r *Backfiller) backfillViaFederation(ctx context.Context, req *api.PerformBackfillRequest, res *api.PerformBackfillResponse) error { info, err := r.DB.RoomInfo(ctx, req.RoomID) if err != nil { return err } if info == nil || info.IsStub { return fmt.Errorf("backfillViaFederation: missing room info for room %s", req.RoomID) } requester := newBackfillRequester(r.DB, r.FedClient, r.ServerName, req.BackwardsExtremities) // Request 100 items regardless of what the query asks for. // We don't want to go much higher than this. // We can't honour exactly the limit as some sytests rely on requesting more for tests to pass // (so we don't need to hit /state_ids which the test has no listener for) // Specifically the test "Outbound federation can backfill events" events, err := gomatrixserverlib.RequestBackfill( ctx, requester, r.KeyRing, req.RoomID, info.RoomVersion, req.PrevEventIDs(), 100) if err != nil { return err } logrus.WithField("room_id", req.RoomID).Infof("backfilled %d events", len(events)) // persist these new events - auth checks have already been done roomNID, backfilledEventMap := persistEvents(ctx, r.DB, events) if err != nil { return err } for _, ev := range backfilledEventMap { // now add state for these events stateIDs, ok := requester.eventIDToBeforeStateIDs[ev.EventID()] if !ok { // this should be impossible as all events returned must have pass Step 5 of the PDU checks // which requires a list of state IDs. logrus.WithError(err).WithField("event_id", ev.EventID()).Error("backfillViaFederation: failed to find state IDs for event which passed auth checks") continue } var entries []types.StateEntry if entries, err = r.DB.StateEntriesForEventIDs(ctx, stateIDs); err != nil { // attempt to fetch the missing events r.fetchAndStoreMissingEvents(ctx, info.RoomVersion, requester, stateIDs) // try again entries, err = r.DB.StateEntriesForEventIDs(ctx, stateIDs) if err != nil { logrus.WithError(err).WithField("event_id", ev.EventID()).Error("backfillViaFederation: failed to get state entries for event") return err } } var beforeStateSnapshotNID types.StateSnapshotNID if beforeStateSnapshotNID, err = r.DB.AddState(ctx, roomNID, nil, entries); err != nil { logrus.WithError(err).WithField("event_id", ev.EventID()).Error("backfillViaFederation: failed to persist state entries to get snapshot nid") return err } if err = r.DB.SetState(ctx, ev.EventNID, beforeStateSnapshotNID); err != nil { logrus.WithError(err).WithField("event_id", ev.EventID()).Error("backfillViaFederation: failed to persist snapshot nid") } } // TODO: update backwards extremities, as that should be moved from syncapi to roomserver at some point. res.Events = events return nil } // fetchAndStoreMissingEvents does a best-effort fetch and store of missing events specified in stateIDs. Returns no error as it is just // best effort. func (r *Backfiller) fetchAndStoreMissingEvents(ctx context.Context, roomVer gomatrixserverlib.RoomVersion, backfillRequester *backfillRequester, stateIDs []string) { servers := backfillRequester.servers // work out which are missing nidMap, err := r.DB.EventNIDs(ctx, stateIDs) if err != nil { util.GetLogger(ctx).WithError(err).Warn("cannot query missing events") return } missingMap := make(map[string]*gomatrixserverlib.HeaderedEvent) // id -> event for _, id := range stateIDs { if _, ok := nidMap[id]; !ok { missingMap[id] = nil } } util.GetLogger(ctx).Infof("Fetching %d missing state events (from %d possible servers)", len(missingMap), len(servers)) // fetch the events from federation. Loop the servers first so if we find one that works we stick with them for _, srv := range servers { for id, ev := range missingMap { if ev != nil { continue // already found } logger := util.GetLogger(ctx).WithField("server", srv).WithField("event_id", id) res, err := r.FedClient.GetEvent(ctx, srv, id) if err != nil { logger.WithError(err).Warn("failed to get event from server") continue } loader := gomatrixserverlib.NewEventsLoader(roomVer, r.KeyRing, backfillRequester, backfillRequester.ProvideEvents, false) result, err := loader.LoadAndVerify(ctx, res.PDUs, gomatrixserverlib.TopologicalOrderByPrevEvents) if err != nil { logger.WithError(err).Warn("failed to load and verify event") continue } logger.Infof("returned %d PDUs which made events %+v", len(res.PDUs), result) for _, res := range result { if res.Error != nil { logger.WithError(err).Warn("event failed PDU checks") continue } missingMap[id] = res.Event } } } var newEvents []gomatrixserverlib.HeaderedEvent for _, ev := range missingMap { if ev != nil { newEvents = append(newEvents, *ev) } } util.GetLogger(ctx).Infof("Persisting %d new events", len(newEvents)) persistEvents(ctx, r.DB, newEvents) } // backfillRequester implements gomatrixserverlib.BackfillRequester type backfillRequester struct { db storage.Database fedClient *gomatrixserverlib.FederationClient thisServer gomatrixserverlib.ServerName bwExtrems map[string][]string // per-request state servers []gomatrixserverlib.ServerName eventIDToBeforeStateIDs map[string][]string eventIDMap map[string]gomatrixserverlib.Event } func newBackfillRequester(db storage.Database, fedClient *gomatrixserverlib.FederationClient, thisServer gomatrixserverlib.ServerName, bwExtrems map[string][]string) *backfillRequester { return &backfillRequester{ db: db, fedClient: fedClient, thisServer: thisServer, eventIDToBeforeStateIDs: make(map[string][]string), eventIDMap: make(map[string]gomatrixserverlib.Event), bwExtrems: bwExtrems, } } func (b *backfillRequester) StateIDsBeforeEvent(ctx context.Context, targetEvent gomatrixserverlib.HeaderedEvent) ([]string, error) { b.eventIDMap[targetEvent.EventID()] = targetEvent.Unwrap() if ids, ok := b.eventIDToBeforeStateIDs[targetEvent.EventID()]; ok { return ids, nil } if len(targetEvent.PrevEventIDs()) == 0 && targetEvent.Type() == "m.room.create" && targetEvent.StateKeyEquals("") { util.GetLogger(ctx).WithField("room_id", targetEvent.RoomID()).Info("Backfilled to the beginning of the room") b.eventIDToBeforeStateIDs[targetEvent.EventID()] = []string{} return nil, nil } // if we have exactly 1 prev event and we know the state of the room at that prev event, then just roll forward the prev event. // Else, we have to hit /state_ids because either we don't know the state at all at this event (new backwards extremity) or // we don't know the result of state res to merge forks (2 or more prev_events) if len(targetEvent.PrevEventIDs()) == 1 { prevEventID := targetEvent.PrevEventIDs()[0] prevEvent, ok := b.eventIDMap[prevEventID] if !ok { goto FederationHit } prevEventStateIDs, ok := b.eventIDToBeforeStateIDs[prevEventID] if !ok { goto FederationHit } newStateIDs := b.calculateNewStateIDs(targetEvent.Unwrap(), prevEvent, prevEventStateIDs) if newStateIDs != nil { b.eventIDToBeforeStateIDs[targetEvent.EventID()] = newStateIDs return newStateIDs, nil } // else we failed to calculate the new state, so fallthrough } FederationHit: var lastErr error logrus.WithField("event_id", targetEvent.EventID()).Info("Requesting /state_ids at event") for _, srv := range b.servers { // hit any valid server c := gomatrixserverlib.FederatedStateProvider{ FedClient: b.fedClient, RememberAuthEvents: false, Server: srv, } res, err := c.StateIDsBeforeEvent(ctx, targetEvent) if err != nil { lastErr = err continue } b.eventIDToBeforeStateIDs[targetEvent.EventID()] = res return res, nil } return nil, lastErr } func (b *backfillRequester) calculateNewStateIDs(targetEvent, prevEvent gomatrixserverlib.Event, prevEventStateIDs []string) []string { newStateIDs := prevEventStateIDs[:] if prevEvent.StateKey() == nil { // state is the same as the previous event b.eventIDToBeforeStateIDs[targetEvent.EventID()] = newStateIDs return newStateIDs } missingState := false // true if we are missing the info for a state event ID foundEvent := false // true if we found a (type, state_key) match // find which state ID to replace, if any for i, id := range newStateIDs { ev, ok := b.eventIDMap[id] if !ok { missingState = true continue } // The state IDs BEFORE the target event are the state IDs BEFORE the prev_event PLUS the prev_event itself if ev.Type() == prevEvent.Type() && ev.StateKeyEquals(*prevEvent.StateKey()) { newStateIDs[i] = prevEvent.EventID() foundEvent = true break } } if !foundEvent && !missingState { // we can be certain that this is new state newStateIDs = append(newStateIDs, prevEvent.EventID()) foundEvent = true } if foundEvent { b.eventIDToBeforeStateIDs[targetEvent.EventID()] = newStateIDs return newStateIDs } return nil } func (b *backfillRequester) StateBeforeEvent(ctx context.Context, roomVer gomatrixserverlib.RoomVersion, event gomatrixserverlib.HeaderedEvent, eventIDs []string) (map[string]*gomatrixserverlib.Event, error) { // try to fetch the events from the database first events, err := b.ProvideEvents(roomVer, eventIDs) if err != nil { // non-fatal, fallthrough logrus.WithError(err).Info("Failed to fetch events") } else { logrus.Infof("Fetched %d/%d events from the database", len(events), len(eventIDs)) if len(events) == len(eventIDs) { result := make(map[string]*gomatrixserverlib.Event) for i := range events { result[events[i].EventID()] = &events[i] b.eventIDMap[events[i].EventID()] = events[i] } return result, nil } } c := gomatrixserverlib.FederatedStateProvider{ FedClient: b.fedClient, RememberAuthEvents: false, Server: b.servers[0], } result, err := c.StateBeforeEvent(ctx, roomVer, event, eventIDs) if err != nil { return nil, err } for eventID, ev := range result { b.eventIDMap[eventID] = *ev } return result, nil } // ServersAtEvent is called when trying to determine which server to request from. // It returns a list of servers which can be queried for backfill requests. These servers // will be servers that are in the room already. The entries at the beginning are preferred servers // and will be tried first. An empty list will fail the request. // nolint:gocyclo func (b *backfillRequester) ServersAtEvent(ctx context.Context, roomID, eventID string) []gomatrixserverlib.ServerName { // eventID will be a prev_event ID of a backwards extremity, meaning we will not have a database entry for it. Instead, use // its successor, so look it up. successor := "" FindSuccessor: for sucID, prevEventIDs := range b.bwExtrems { for _, pe := range prevEventIDs { if pe == eventID { successor = sucID break FindSuccessor } } } if successor == "" { logrus.WithField("event_id", eventID).Error("ServersAtEvent: failed to find successor of this event to determine room state") return nil } eventID = successor // getMembershipsBeforeEventNID requires a NID, so retrieving the NID for // the event is necessary. NIDs, err := b.db.EventNIDs(ctx, []string{eventID}) if err != nil { logrus.WithField("event_id", eventID).WithError(err).Error("ServersAtEvent: failed to get event NID for event") return nil } info, err := b.db.RoomInfo(ctx, roomID) if err != nil { logrus.WithError(err).WithField("room_id", roomID).Error("ServersAtEvent: failed to get RoomInfo for room") return nil } if info == nil || info.IsStub { logrus.WithField("room_id", roomID).Error("ServersAtEvent: failed to get RoomInfo for room, room is missing") return nil } stateEntries, err := helpers.StateBeforeEvent(ctx, b.db, *info, NIDs[eventID]) if err != nil { logrus.WithField("event_id", eventID).WithError(err).Error("ServersAtEvent: failed to load state before event") return nil } // possibly return all joined servers depending on history visiblity memberEventsFromVis, err := joinEventsFromHistoryVisibility(ctx, b.db, roomID, stateEntries) if err != nil { logrus.WithError(err).Error("ServersAtEvent: failed calculate servers from history visibility rules") return nil } logrus.Infof("ServersAtEvent including %d current events from history visibility", len(memberEventsFromVis)) // Retrieve all "m.room.member" state events of "join" membership, which // contains the list of users in the room before the event, therefore all // the servers in it at that moment. memberEvents, err := helpers.GetMembershipsAtState(ctx, b.db, stateEntries, true) if err != nil { logrus.WithField("event_id", eventID).WithError(err).Error("ServersAtEvent: failed to get memberships before event") return nil } memberEvents = append(memberEvents, memberEventsFromVis...) // Store the server names in a temporary map to avoid duplicates. serverSet := make(map[gomatrixserverlib.ServerName]bool) for _, event := range memberEvents { serverSet[event.Origin()] = true } var servers []gomatrixserverlib.ServerName for server := range serverSet { if server == b.thisServer { continue } servers = append(servers, server) } b.servers = servers return servers } // Backfill performs a backfill request to the given server. // https://matrix.org/docs/spec/server_server/latest#get-matrix-federation-v1-backfill-roomid func (b *backfillRequester) Backfill(ctx context.Context, server gomatrixserverlib.ServerName, roomID string, fromEventIDs []string, limit int) (*gomatrixserverlib.Transaction, error) { tx, err := b.fedClient.Backfill(ctx, server, roomID, limit, fromEventIDs) return &tx, err } func (b *backfillRequester) ProvideEvents(roomVer gomatrixserverlib.RoomVersion, eventIDs []string) ([]gomatrixserverlib.Event, error) { ctx := context.Background() nidMap, err := b.db.EventNIDs(ctx, eventIDs) if err != nil { logrus.WithError(err).WithField("event_ids", eventIDs).Error("Failed to find events") return nil, err } eventNIDs := make([]types.EventNID, len(nidMap)) i := 0 for _, nid := range nidMap { eventNIDs[i] = nid i++ } eventsWithNids, err := b.db.Events(ctx, eventNIDs) if err != nil { logrus.WithError(err).WithField("event_nids", eventNIDs).Error("Failed to load events") return nil, err } events := make([]gomatrixserverlib.Event, len(eventsWithNids)) for i := range eventsWithNids { events[i] = eventsWithNids[i].Event } return events, nil } // joinEventsFromHistoryVisibility returns all CURRENTLY joined members if the provided state indicated a 'shared' history visibility. // TODO: Long term we probably want a history_visibility table which stores eventNID | visibility_enum so we can just // pull all events and then filter by that table. func joinEventsFromHistoryVisibility( ctx context.Context, db storage.Database, roomID string, stateEntries []types.StateEntry) ([]types.Event, error) { var eventNIDs []types.EventNID for _, entry := range stateEntries { // Filter the events to retrieve to only keep the membership events if entry.EventTypeNID == types.MRoomHistoryVisibilityNID && entry.EventStateKeyNID == types.EmptyStateKeyNID { eventNIDs = append(eventNIDs, entry.EventNID) break } } // Get all of the events in this state stateEvents, err := db.Events(ctx, eventNIDs) if err != nil { return nil, err } events := make([]gomatrixserverlib.Event, len(stateEvents)) for i := range stateEvents { events[i] = stateEvents[i].Event } visibility := auth.HistoryVisibilityForRoom(events) if visibility != "shared" { logrus.Infof("ServersAtEvent history visibility not shared: %s", visibility) return nil, nil } // get joined members info, err := db.RoomInfo(ctx, roomID) if err != nil { return nil, err } joinEventNIDs, err := db.GetMembershipEventNIDsForRoom(ctx, info.RoomNID, true, false) if err != nil { return nil, err } return db.Events(ctx, joinEventNIDs) } func persistEvents(ctx context.Context, db storage.Database, events []gomatrixserverlib.HeaderedEvent) (types.RoomNID, map[string]types.Event) { var roomNID types.RoomNID backfilledEventMap := make(map[string]types.Event) for j, ev := range events { nidMap, err := db.EventNIDs(ctx, ev.AuthEventIDs()) if err != nil { // this shouldn't happen as RequestBackfill already found them logrus.WithError(err).WithField("auth_events", ev.AuthEventIDs()).Error("Failed to find one or more auth events") continue } authNids := make([]types.EventNID, len(nidMap)) i := 0 for _, nid := range nidMap { authNids[i] = nid i++ } var stateAtEvent types.StateAtEvent var redactedEventID string var redactionEvent *gomatrixserverlib.Event roomNID, stateAtEvent, redactionEvent, redactedEventID, err = db.StoreEvent(ctx, ev.Unwrap(), nil, authNids) if err != nil { logrus.WithError(err).WithField("event_id", ev.EventID()).Error("Failed to persist event") continue } // If storing this event results in it being redacted, then do so. // It's also possible for this event to be a redaction which results in another event being // redacted, which we don't care about since we aren't returning it in this backfill. if redactedEventID == ev.EventID() { eventToRedact := ev.Unwrap() redactedEvent, err := eventutil.RedactEvent(redactionEvent, &eventToRedact) if err != nil { logrus.WithError(err).WithField("event_id", ev.EventID()).Error("Failed to redact event") continue } ev = redactedEvent.Headered(ev.RoomVersion) events[j] = ev } backfilledEventMap[ev.EventID()] = types.Event{ EventNID: stateAtEvent.StateEntry.EventNID, Event: ev.Unwrap(), } } return roomNID, backfilledEventMap }