dendrite/roomserver/internal/perform/perform_backfill.go

671 lines
25 KiB
Go

// Copyright 2020 The Matrix.org Foundation C.I.C.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package perform
import (
"context"
"fmt"
"github.com/matrix-org/gomatrixserverlib"
"github.com/matrix-org/gomatrixserverlib/spec"
"github.com/matrix-org/util"
"github.com/sirupsen/logrus"
federationAPI "github.com/matrix-org/dendrite/federationapi/api"
"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/state"
"github.com/matrix-org/dendrite/roomserver/storage"
"github.com/matrix-org/dendrite/roomserver/types"
)
// the max number of servers to backfill from per request. If this is too low we may fail to backfill when
// we could've from another server. If this is too high we may take far too long to successfully backfill
// as we try dead servers.
const maxBackfillServers = 5
type Backfiller struct {
IsLocalServerName func(spec.ServerName) bool
DB storage.Database
FSAPI federationAPI.RoomserverFederationAPI
KeyRing gomatrixserverlib.JSONVerifier
Querier api.QuerySenderIDAPI
// The servers which should be preferred above other servers when backfilling
PreferServers []spec.ServerName
}
// 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 r.IsLocalServerName(request.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, redactEventIDs, err := helpers.ScanEventTree(ctx, r.DB, info, front, visited, request.Limit, request.ServerName, r.Querier)
if err != nil {
return err
}
// Retrieve events from the list that was filled previously. If we fail to get
// events from the database then attempt once to get them from federation instead.
var loadedEvents []gomatrixserverlib.PDU
loadedEvents, err = helpers.LoadEvents(ctx, r.DB, info, resultNIDs)
if err != nil {
if _, ok := err.(types.MissingEventError); ok {
return r.backfillViaFederation(ctx, request, response)
}
return err
}
for _, event := range loadedEvents {
if _, ok := redactEventIDs[event.EventID()]; ok {
event.Redact()
}
response.Events = append(response.Events, &types.HeaderedEvent{PDU: event})
}
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.FSAPI, r.Querier, req.VirtualHost, r.IsLocalServerName, req.BackwardsExtremities, r.PreferServers)
// 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, req.VirtualHost, requester,
r.KeyRing, req.RoomID, info.RoomVersion, req.PrevEventIDs(), 100, func(roomID spec.RoomID, senderID spec.SenderID) (*spec.UserID, error) {
return r.Querier.QueryUserIDForSender(ctx, roomID, senderID)
},
)
// Only return an error if we really couldn't get any events.
if err != nil && len(events) == 0 {
logrus.WithError(err).Errorf("gomatrixserverlib.RequestBackfill failed")
return err
}
// If we got an error but still got events, that's fine, because a server might have returned a 404 (or something)
// but other servers could provide the missing event.
logrus.WithError(err).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, r.Querier, events)
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, true); err != nil {
// attempt to fetch the missing events
r.fetchAndStoreMissingEvents(ctx, info.RoomVersion, requester, stateIDs, req.VirtualHost)
// try again
entries, err = r.DB.StateEntriesForEventIDs(ctx, stateIDs, true)
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 = make([]*types.HeaderedEvent, len(events))
for i := range events {
res.Events[i] = &types.HeaderedEvent{PDU: events[i]}
}
res.HistoryVisibility = requester.historyVisiblity
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, virtualHost spec.ServerName) {
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]*types.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.FSAPI.GetEvent(ctx, virtualHost, 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, func(roomID spec.RoomID, senderID spec.SenderID) (*spec.UserID, error) {
return r.Querier.QueryUserIDForSender(ctx, roomID, senderID)
})
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 {
switch err := res.Error.(type) {
case nil:
case gomatrixserverlib.SignatureErr:
// The signature of the event might not be valid anymore, for example if
// the key ID was reused with a different signature.
logger.WithError(err).Errorf("event failed PDU checks, storing anyway")
case gomatrixserverlib.AuthChainErr, gomatrixserverlib.AuthRulesErr:
logger.WithError(err).Warn("event failed PDU checks")
continue
default:
logger.WithError(err).Warn("event failed PDU checks")
continue
}
missingMap[id] = &types.HeaderedEvent{PDU: res.Event}
}
}
}
var newEvents []gomatrixserverlib.PDU
for _, ev := range missingMap {
if ev != nil {
newEvents = append(newEvents, ev.PDU)
}
}
util.GetLogger(ctx).Infof("Persisting %d new events", len(newEvents))
persistEvents(ctx, r.DB, r.Querier, newEvents)
}
// backfillRequester implements gomatrixserverlib.BackfillRequester
type backfillRequester struct {
db storage.Database
fsAPI federationAPI.RoomserverFederationAPI
querier api.QuerySenderIDAPI
virtualHost spec.ServerName
isLocalServerName func(spec.ServerName) bool
preferServer map[spec.ServerName]bool
bwExtrems map[string][]string
// per-request state
servers []spec.ServerName
eventIDToBeforeStateIDs map[string][]string
eventIDMap map[string]gomatrixserverlib.PDU
historyVisiblity gomatrixserverlib.HistoryVisibility
roomInfo types.RoomInfo
}
func newBackfillRequester(
db storage.Database, fsAPI federationAPI.RoomserverFederationAPI,
querier api.QuerySenderIDAPI,
virtualHost spec.ServerName,
isLocalServerName func(spec.ServerName) bool,
bwExtrems map[string][]string, preferServers []spec.ServerName,
) *backfillRequester {
preferServer := make(map[spec.ServerName]bool)
for _, p := range preferServers {
preferServer[p] = true
}
return &backfillRequester{
db: db,
fsAPI: fsAPI,
querier: querier,
virtualHost: virtualHost,
isLocalServerName: isLocalServerName,
eventIDToBeforeStateIDs: make(map[string][]string),
eventIDMap: make(map[string]gomatrixserverlib.PDU),
bwExtrems: bwExtrems,
preferServer: preferServer,
historyVisiblity: gomatrixserverlib.HistoryVisibilityShared,
}
}
func (b *backfillRequester) StateIDsBeforeEvent(ctx context.Context, targetEvent gomatrixserverlib.PDU) ([]string, error) {
b.eventIDMap[targetEvent.EventID()] = targetEvent
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, 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.fsAPI,
RememberAuthEvents: false,
Server: srv,
Origin: b.virtualHost,
}
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.PDU, 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.PDU, eventIDs []string) (map[string]gomatrixserverlib.PDU, 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.PDU)
for i := range events {
result[events[i].EventID()] = events[i]
b.eventIDMap[events[i].EventID()] = events[i]
}
return result, nil
}
}
var lastErr error
for _, srv := range b.servers {
c := gomatrixserverlib.FederatedStateProvider{
FedClient: b.fsAPI,
RememberAuthEvents: false,
Server: srv,
Origin: b.virtualHost,
}
result, err := c.StateBeforeEvent(ctx, roomVer, event, eventIDs)
if err != nil {
lastErr = err
continue
}
for eventID, ev := range result {
b.eventIDMap[eventID] = ev
}
return result, nil
}
return nil, lastErr
}
// 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.
func (b *backfillRequester) ServersAtEvent(ctx context.Context, roomID, eventID string) []spec.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].EventNID, b.querier)
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, visibility, err := joinEventsFromHistoryVisibility(ctx, b.db, b.querier, info, stateEntries, b.virtualHost)
b.historyVisiblity = visibility
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, info, 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[spec.ServerName]bool)
for _, event := range memberEvents {
validRoomID, err := spec.NewRoomID(event.RoomID())
if err != nil {
continue
}
if sender, err := b.querier.QueryUserIDForSender(ctx, *validRoomID, event.SenderID()); err == nil {
serverSet[sender.Domain()] = true
}
}
var servers []spec.ServerName
for server := range serverSet {
if b.isLocalServerName(server) {
continue
}
if b.preferServer[server] { // insert at the front
servers = append([]spec.ServerName{server}, servers...)
} else { // insert at the back
servers = append(servers, server)
}
}
if len(servers) > maxBackfillServers {
servers = servers[:maxBackfillServers]
}
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, origin, server spec.ServerName, roomID string,
limit int, fromEventIDs []string) (gomatrixserverlib.Transaction, error) {
tx, err := b.fsAPI.Backfill(ctx, origin, server, roomID, limit, fromEventIDs)
return tx, err
}
func (b *backfillRequester) ProvideEvents(roomVer gomatrixserverlib.RoomVersion, eventIDs []string) ([]gomatrixserverlib.PDU, 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
roomNID := b.roomInfo.RoomNID
for _, nid := range nidMap {
eventNIDs[i] = nid.EventNID
i++
if roomNID == 0 {
roomNID = nid.RoomNID
}
}
eventsWithNids, err := b.db.Events(ctx, b.roomInfo.RoomVersion, eventNIDs)
if err != nil {
logrus.WithError(err).WithField("event_nids", eventNIDs).Error("Failed to load events")
return nil, err
}
events := make([]gomatrixserverlib.PDU, len(eventsWithNids))
for i := range eventsWithNids {
events[i] = eventsWithNids[i].PDU
}
return events, nil
}
// joinEventsFromHistoryVisibility returns all CURRENTLY joined members if our server can read the room history
//
// 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.RoomDatabase, querier api.QuerySenderIDAPI, roomInfo *types.RoomInfo, stateEntries []types.StateEntry,
thisServer spec.ServerName) ([]types.Event, gomatrixserverlib.HistoryVisibility, 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
if roomInfo == nil {
return nil, gomatrixserverlib.HistoryVisibilityJoined, types.ErrorInvalidRoomInfo
}
stateEvents, err := db.Events(ctx, roomInfo.RoomVersion, eventNIDs)
if err != nil {
// even though the default should be shared, restricting the visibility to joined
// feels more secure here.
return nil, gomatrixserverlib.HistoryVisibilityJoined, err
}
events := make([]gomatrixserverlib.PDU, len(stateEvents))
for i := range stateEvents {
events[i] = stateEvents[i].PDU
}
// Can we see events in the room?
canSeeEvents := auth.IsServerAllowed(ctx, querier, thisServer, true, events)
visibility := auth.HistoryVisibilityForRoom(events)
if !canSeeEvents {
logrus.Infof("ServersAtEvent history not visible to us: %s", visibility)
return nil, visibility, nil
}
// get joined members
joinEventNIDs, err := db.GetMembershipEventNIDsForRoom(ctx, roomInfo.RoomNID, true, false)
if err != nil {
return nil, visibility, err
}
evs, err := db.Events(ctx, roomInfo.RoomVersion, joinEventNIDs)
return evs, visibility, err
}
func persistEvents(ctx context.Context, db storage.Database, querier api.QuerySenderIDAPI, events []gomatrixserverlib.PDU) (types.RoomNID, map[string]types.Event) {
var roomNID types.RoomNID
var eventNID types.EventNID
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.EventNID
i++
}
roomInfo, err := db.GetOrCreateRoomInfo(ctx, ev)
if err != nil {
logrus.WithError(err).Error("failed to get or create roomNID")
continue
}
roomNID = roomInfo.RoomNID
eventTypeNID, err := db.GetOrCreateEventTypeNID(ctx, ev.Type())
if err != nil {
logrus.WithError(err).Error("failed to get or create eventType NID")
continue
}
eventStateKeyNID, err := db.GetOrCreateEventStateKeyNID(ctx, ev.StateKey())
if err != nil {
logrus.WithError(err).Error("failed to get or create eventStateKey NID")
continue
}
eventNID, _, err = db.StoreEvent(ctx, ev, roomInfo, eventTypeNID, eventStateKeyNID, authNids, false)
if err != nil {
logrus.WithError(err).WithField("event_id", ev.EventID()).Error("Failed to persist event")
continue
}
resolver := state.NewStateResolution(db, roomInfo, querier)
_, redactedEvent, err := db.MaybeRedactEvent(ctx, roomInfo, eventNID, ev, &resolver)
if err != nil {
logrus.WithError(err).WithField("event_id", ev.EventID()).Error("Failed to redact 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 redactedEvent != nil && redactedEvent.EventID() == ev.EventID() {
ev = redactedEvent
events[j] = ev
}
backfilledEventMap[ev.EventID()] = types.Event{
EventNID: eventNID,
PDU: ev,
}
}
return roomNID, backfilledEventMap
}