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dendrite/roomserver/internal/perform/perform_backfill.go
Till 365da70a23
Set historyVisibility for backfilled events over federation (#2656)
This should hopefully deflake Backfill works correctly with history visibility set to joined as we were using the default shared visibility, even if the events are set to joined (or something else)
2022-08-19 11:04:26 +02:00

620 lines
23 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/getsentry/sentry-go"
"github.com/matrix-org/gomatrixserverlib"
"github.com/matrix-org/util"
"github.com/sirupsen/logrus"
federationAPI "github.com/matrix-org/dendrite/federationapi/api"
"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"
)
// 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 {
ServerName gomatrixserverlib.ServerName
DB storage.Database
FSAPI federationAPI.RoomserverFederationAPI
KeyRing gomatrixserverlib.JSONVerifier
// The servers which should be preferred above other servers when backfilling
PreferServers []gomatrixserverlib.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 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. If we fail to get
// events from the database then attempt once to get them from federation instead.
var loadedEvents []*gomatrixserverlib.Event
loadedEvents, err = helpers.LoadEvents(ctx, r.DB, resultNIDs)
if err != nil {
if _, ok := err.(types.MissingEventError); ok {
return r.backfillViaFederation(ctx, request, response)
}
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.FSAPI, r.ServerName, 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, 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, true); err != nil {
// attempt to fetch the missing events
r.fetchAndStoreMissingEvents(ctx, info.RoomVersion, requester, stateIDs)
// 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 = events
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) {
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.FSAPI.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 {
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] = 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
fsAPI federationAPI.RoomserverFederationAPI
thisServer gomatrixserverlib.ServerName
preferServer map[gomatrixserverlib.ServerName]bool
bwExtrems map[string][]string
// per-request state
servers []gomatrixserverlib.ServerName
eventIDToBeforeStateIDs map[string][]string
eventIDMap map[string]*gomatrixserverlib.Event
historyVisiblity gomatrixserverlib.HistoryVisibility
}
func newBackfillRequester(
db storage.Database, fsAPI federationAPI.RoomserverFederationAPI, thisServer gomatrixserverlib.ServerName,
bwExtrems map[string][]string, preferServers []gomatrixserverlib.ServerName,
) *backfillRequester {
preferServer := make(map[gomatrixserverlib.ServerName]bool)
for _, p := range preferServers {
preferServer[p] = true
}
return &backfillRequester{
db: db,
fsAPI: fsAPI,
thisServer: thisServer,
eventIDToBeforeStateIDs: make(map[string][]string),
eventIDMap: make(map[string]*gomatrixserverlib.Event),
bwExtrems: bwExtrems,
preferServer: preferServer,
historyVisiblity: gomatrixserverlib.HistoryVisibilityShared,
}
}
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.fsAPI,
RememberAuthEvents: false,
Server: srv,
}
res, err := c.StateIDsBeforeEvent(ctx, targetEvent)
if err != nil {
lastErr = err
continue
}
b.eventIDToBeforeStateIDs[targetEvent.EventID()] = res
return res, nil
}
sentry.CaptureException(lastErr) // temporary to see if we might need to raise the server limit
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
}
}
var lastErr error
for _, srv := range b.servers {
c := gomatrixserverlib.FederatedStateProvider{
FedClient: b.fsAPI,
RememberAuthEvents: false,
Server: srv,
}
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
}
sentry.CaptureException(lastErr) // temporary to see if we might need to raise the server limit
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) []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, visibility, err := joinEventsFromHistoryVisibility(ctx, b.db, roomID, stateEntries, b.thisServer)
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, 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
}
if b.preferServer[server] { // insert at the front
servers = append([]gomatrixserverlib.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, server gomatrixserverlib.ServerName, roomID string,
limit int, fromEventIDs []string) (gomatrixserverlib.Transaction, error) {
tx, err := b.fsAPI.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 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.Database, roomID string, stateEntries []types.StateEntry,
thisServer gomatrixserverlib.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
stateEvents, err := db.Events(ctx, 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.Event, len(stateEvents))
for i := range stateEvents {
events[i] = stateEvents[i].Event
}
// Can we see events in the room?
canSeeEvents := auth.IsServerAllowed(thisServer, true, events)
visibility := gomatrixserverlib.HistoryVisibility(auth.HistoryVisibilityForRoom(events))
if !canSeeEvents {
logrus.Infof("ServersAtEvent history not visible to us: %s", visibility)
return nil, visibility, nil
}
// get joined members
info, err := db.RoomInfo(ctx, roomID)
if err != nil {
return nil, visibility, nil
}
joinEventNIDs, err := db.GetMembershipEventNIDsForRoom(ctx, info.RoomNID, true, false)
if err != nil {
return nil, visibility, err
}
evs, err := db.Events(ctx, joinEventNIDs)
return evs, visibility, err
}
func persistEvents(ctx context.Context, db storage.Database, events []*gomatrixserverlib.HeaderedEvent) (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
i++
}
var redactedEventID string
var redactionEvent *gomatrixserverlib.Event
eventNID, roomNID, _, redactionEvent, redactedEventID, err = db.StoreEvent(ctx, ev.Unwrap(), authNids, false)
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()
if err := eventutil.RedactEvent(redactionEvent, eventToRedact); err != nil {
logrus.WithError(err).WithField("event_id", ev.EventID()).Error("Failed to redact event")
continue
}
ev = eventToRedact.Headered(ev.RoomVersion)
events[j] = ev
}
backfilledEventMap[ev.EventID()] = types.Event{
EventNID: eventNID,
Event: ev.Unwrap(),
}
}
return roomNID, backfilledEventMap
}