Partially implement lazy loading on /sync

internal/caching/cache_lazy_load_members.go

@@ -0,0 +1,49 @@
+package caching
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+const (
+	LazyLoadCacheName       = "lazy_load_members"
+	LazyLoadCacheMaxEntries = 128
+	LazyLoadCacheMutable    = true
+	LazyLoadCacheMaxAge     = time.Minute * 30
+)
+
+type LazyLoadCache struct {
+	*InMemoryLRUCachePartition
+}
+
+// NewLazyLoadCache creates a new InMemoryLRUCachePartition.
+func NewLazyLoadCache() (*LazyLoadCache, error) {
+	cache, err := NewInMemoryLRUCachePartition(
+		LazyLoadCacheName,
+		LazyLoadCacheMutable,
+		LazyLoadCacheMaxEntries,
+		LazyLoadCacheMaxAge,
+		false,
+	)
+	if err != nil {
+		return nil, err
+	}
+	go cacheCleaner(cache)
+	return &LazyLoadCache{cache}, err
+}
+
+func (c *LazyLoadCache) StoreLazyLoadedMembers(reqUser, deviceID, roomID, userID string, event *gomatrixserverlib.HeaderedEvent) {
+	cacheKey := fmt.Sprintf("%s/%s/%s/%s", reqUser, deviceID, roomID, userID)
+	c.Set(cacheKey, event)
+}
+
+func (c *LazyLoadCache) GetLazyLoadedMembers(reqUser, deviceID, roomID, userID string) (*gomatrixserverlib.HeaderedEvent, bool) {
+	cacheKey := fmt.Sprintf("%s/%s/%s/%s", reqUser, deviceID, roomID, userID)
+	val, ok := c.Get(cacheKey)
+	if !ok {
+		return nil, ok
+	}
+	return val.(*gomatrixserverlib.HeaderedEvent), ok
+}

syncapi/streams/stream_pdu.go

@@ -6,6 +6,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/matrix-org/dendrite/internal/caching"
 	"github.com/matrix-org/dendrite/syncapi/types"
 	userapi "github.com/matrix-org/dendrite/userapi/api"
 	"github.com/matrix-org/gomatrixserverlib"
@@ -26,7 +27,8 @@ type PDUStreamProvider struct {
 
 	tasks   chan func()
 	workers atomic.Int32
-	userAPI userapi.UserInternalAPI
+	// userID+deviceID -> lazy loading cache
+	lazyLoadCache map[string]*caching.LazyLoadCache
 }
 
 func (p *PDUStreamProvider) worker() {
@@ -188,7 +190,7 @@ func (p *PDUStreamProvider) IncrementalSync(
 	newPos = from
 	for _, delta := range stateDeltas {
 		var pos types.StreamPosition
-		if pos, err = p.addRoomDeltaToResponse(ctx, req.Device, r, delta, &eventFilter, req.Response); err != nil {
+		if pos, err = p.addRoomDeltaToResponse(ctx, req.Device, r, delta, &eventFilter, &stateFilter, req.Response); err != nil {
 			req.Log.WithError(err).Error("d.addRoomDeltaToResponse failed")
 			return to
 		}
@@ -209,6 +211,7 @@ func (p *PDUStreamProvider) addRoomDeltaToResponse(
 	r types.Range,
 	delta types.StateDelta,
 	eventFilter *gomatrixserverlib.RoomEventFilter,
+	stateFilter *gomatrixserverlib.StateFilter,
 	res *types.Response,
 ) (types.StreamPosition, error) {
 	if delta.MembershipPos > 0 && delta.Membership == gomatrixserverlib.Leave {
@@ -263,6 +266,17 @@ func (p *PDUStreamProvider) addRoomDeltaToResponse(
 		updateLatestPosition(delta.StateEvents[len(delta.StateEvents)-1].EventID())
 	}
 
+	if stateFilter.LazyLoadMembers {
+		cache, err := p.getLazyLoadCache(device)
+		if err != nil {
+			return r.From, err
+		}
+		delta.StateEvents, err = p.lazyLoadMembers(ctx, delta.RoomID, true, stateFilter, device, recentEvents, cache, delta.StateEvents)
+		if err != nil {
+			return r.From, err
+		}
+	}
+
 	hasMembershipChange := false
 	for _, recentEvent := range recentStreamEvents {
 		if recentEvent.Type() == gomatrixserverlib.MRoomMember && recentEvent.StateKey() != nil {
@@ -402,6 +416,18 @@ func (p *PDUStreamProvider) getJoinResponseForCompleteSync(
 	// "Can sync a room with a message with a transaction id" - which does a complete sync to check.
 	recentEvents := p.DB.StreamEventsToEvents(device, recentStreamEvents)
 	stateEvents = removeDuplicates(stateEvents, recentEvents)
+
+	if stateFilter.LazyLoadMembers {
+		cache, err := p.getLazyLoadCache(device)
+		if err != nil {
+			return nil, err
+		}
+		stateEvents, err = p.lazyLoadMembers(ctx, roomID, false, stateFilter, device, recentEvents, cache, stateEvents)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	jr = types.NewJoinResponse()
 	jr.Summary.JoinedMemberCount = &joinedCount
 	jr.Summary.InvitedMemberCount = &invitedCount
@@ -412,6 +438,83 @@ func (p *PDUStreamProvider) getJoinResponseForCompleteSync(
 	return jr, nil
 }
 
+func (p *PDUStreamProvider) lazyLoadMembers(
+	ctx context.Context, roomID string, isIncremental bool,
+	stateFilter *gomatrixserverlib.StateFilter, device *userapi.Device,
+	timelineEvents []*gomatrixserverlib.HeaderedEvent, cache *caching.LazyLoadCache,
+	stateEvents []*gomatrixserverlib.HeaderedEvent,
+) ([]*gomatrixserverlib.HeaderedEvent, error) {
+	if len(timelineEvents) == 0 {
+		return stateEvents, nil
+	}
+	// Work out if we need to include membership events
+	timelineUsers := make(map[string]struct{})
+
+	if !isIncremental {
+		timelineUsers[device.UserID] = struct{}{}
+	}
+	// add all users the client doesn't know about yet to a list
+	for _, event := range timelineEvents {
+		if event.Type() == gomatrixserverlib.MRoomMember && event.StateKey() != nil {
+			continue
+		}
+		// membership is not yet cached, add it to the list
+		if _, ok := cache.GetLazyLoadedMembers(device.UserID, device.ID, roomID, event.Sender()); !ok {
+			timelineUsers[event.Sender()] = struct{}{}
+		}
+	}
+	// remove existing membership events we don't care about, e.g. users not in the timeline.events
+	newStateEvents := []*gomatrixserverlib.HeaderedEvent{}
+	for _, event := range stateEvents {
+		if event.Type() == gomatrixserverlib.MRoomMember && event.StateKey() != nil {
+			// We want this users membership event, keep it in the list
+			if _, ok := timelineUsers[event.Sender()]; ok {
+				newStateEvents = append(newStateEvents, event)
+				if !stateFilter.IncludeRedundantMembers {
+					cache.StoreLazyLoadedMembers(device.UserID, device.ID, roomID, event.Sender(), event)
+				}
+				delete(timelineUsers, event.Sender())
+			}
+		} else {
+			newStateEvents = append(newStateEvents, event)
+		}
+	}
+
+	wantUsers := make([]string, 0, len(timelineUsers))
+	for userID := range timelineUsers {
+		wantUsers = append(wantUsers, userID)
+	}
+	// Query missing membership events
+	memberships, err := p.DB.GetStateEventsForRoom(ctx, roomID, &gomatrixserverlib.StateFilter{
+		Limit:   100,
+		Senders: &wantUsers,
+		Types:   &[]string{gomatrixserverlib.MRoomMember},
+	})
+	if err != nil {
+		return stateEvents, err
+	}
+	// cache the membership events
+	for _, membership := range memberships {
+		cache.StoreLazyLoadedMembers(device.UserID, device.ID, roomID, membership.Sender(), membership)
+	}
+	stateEvents = append(newStateEvents, memberships...)
+	return stateEvents, nil
+}
+
+func (p *PDUStreamProvider) getLazyLoadCache(device *userapi.Device) (*caching.LazyLoadCache, error) {
+	var err error
+	cacheKey := device.UserID + device.ID
+	cache, ok := p.lazyLoadCache[cacheKey]
+	if !ok {
+		cache, err = caching.NewLazyLoadCache()
+		if err != nil {
+			return nil, err
+		}
+		p.lazyLoadCache[cacheKey] = cache
+	}
+	return cache, nil
+}
+
 // addIgnoredUsersToFilter adds ignored users to the eventfilter and
 // the syncreq itself for further use in streams.
 func (p *PDUStreamProvider) addIgnoredUsersToFilter(ctx context.Context, req *types.SyncRequest, eventFilter *gomatrixserverlib.RoomEventFilter) error {

syncapi/streams/streams.go

@@ -27,12 +27,12 @@ type Streams struct {
 func NewSyncStreamProviders(
 	d storage.Database, userAPI userapi.UserInternalAPI,
 	rsAPI rsapi.RoomserverInternalAPI, keyAPI keyapi.KeyInternalAPI,
-	eduCache *caching.EDUCache, notifier *notifier.Notifier,
+	eduCache *caching.EDUCache, lazyLoadCache map[string]*caching.LazyLoadCache, notifier *notifier.Notifier,
 ) *Streams {
 	streams := &Streams{
 		PDUStreamProvider: &PDUStreamProvider{
 			StreamProvider: StreamProvider{DB: d},
-			userAPI:        userAPI,
+			lazyLoadCache:  lazyLoadCache,
 		},
 		TypingStreamProvider: &TypingStreamProvider{
 			StreamProvider: StreamProvider{DB: d},

syncapi/sync/requestpool.go

@@ -337,71 +337,12 @@ func (rp *RequestPool) OnIncomingSyncRequest(req *http.Request, device *userapi.
 		}
 	}
 
-	if syncReq.Filter.Room.State.LazyLoadMembers {
-		for roomID, jr := range syncReq.Response.Rooms.Join {
-			jr.State.Events = rp.applyLazyLoadMembers(req.Context(), syncReq.Since.IsEmpty(), roomID, syncReq.Device.UserID, jr.Timeline.Events, jr.State.Events)
-			syncReq.Response.Rooms.Join[roomID] = jr
-		}
-	}
-
 	return util.JSONResponse{
 		Code: http.StatusOK,
 		JSON: syncReq.Response,
 	}
 }
 
-func (rp *RequestPool) applyLazyLoadMembers(
-	ctx context.Context, isInitial bool, roomID, userID string, timelineEvents, stateEvents []gomatrixserverlib.ClientEvent,
-) []gomatrixserverlib.ClientEvent {
-	if len(stateEvents) == 0 || len(timelineEvents) == 0 {
-		return stateEvents
-	}
-	logrus.Debugf("before stateEvents: %d", len(stateEvents))
-
-	// First, get a list of users we need in the response
-	requiredUsers := make(map[string]bool)
-	if isInitial {
-		requiredUsers[userID] = true
-	}
-	for _, ev := range timelineEvents {
-		requiredUsers[ev.Sender] = true
-	}
-	// Filter out users who didn't send an event
-	newState := []gomatrixserverlib.ClientEvent{}
-	membershipEvents := []gomatrixserverlib.ClientEvent{}
-	for _, event := range stateEvents {
-		if event.Type != gomatrixserverlib.MRoomMember {
-			newState = append(newState, event)
-		} else {
-			// did the user send an event?
-			if requiredUsers[event.Sender] {
-				membershipEvents = append(membershipEvents, event)
-				delete(requiredUsers, event.Sender)
-			}
-		}
-	}
-	// Get all remaining users in the list
-	membershipToUser := make(map[string]*gomatrixserverlib.HeaderedEvent)
-	for userID := range requiredUsers {
-		membership, err := rp.db.GetStateEvent(ctx, roomID, gomatrixserverlib.MRoomMember, userID)
-		if err != nil {
-			util.GetLogger(ctx).WithError(err).Error("failed to get membership event for user")
-			continue
-		}
-		if membership != nil {
-			membershipToUser[userID] = membership
-		}
-	}
-	// Convert HeaderedEvent to ClientEvent
-	for _, evt := range membershipToUser {
-		newState = append(newState, gomatrixserverlib.HeaderedToClientEvent(evt, gomatrixserverlib.FormatSync))
-	}
-
-	result := append(newState, membershipEvents...)
-	logrus.Debugf("after stateEvents: %d", len(result))
-	return result
-}
-
 func (rp *RequestPool) OnIncomingKeyChangeRequest(req *http.Request, device *userapi.Device) util.JSONResponse {
 	from := req.URL.Query().Get("from")
 	to := req.URL.Query().Get("to")

syncapi/syncapi.go

@@ -58,7 +58,8 @@ func AddPublicRoutes(
 
 	eduCache := caching.NewTypingCache()
 	notifier := notifier.NewNotifier()
-	streams := streams.NewSyncStreamProviders(syncDB, userAPI, rsAPI, keyAPI, eduCache, notifier)
+	lazyLoadCache := make(map[string]*caching.LazyLoadCache)
+	streams := streams.NewSyncStreamProviders(syncDB, userAPI, rsAPI, keyAPI, eduCache, lazyLoadCache, notifier)
 	notifier.SetCurrentPosition(streams.Latest(context.Background()))
 	if err = notifier.Load(context.Background(), syncDB); err != nil {
 		logrus.WithError(err).Panicf("failed to load notifier ")

sytest-whitelist

@@ -698,4 +698,9 @@ Ignore user in existing room
 Ignore invite in full sync
 Ignore invite in incremental sync
 A filtered timeline reaches its limit
-A change to displayname should not result in a full state sync
+A change to displayname should not result in a full state sync
+The only membership state included in an initial sync is for all the senders in the timeline
+The only membership state included in an incremental sync is for senders in the timeline
+Old members are included in gappy incr LL sync if they start speaking
+We do send redundant membership state across incremental syncs if asked
+Rejecting invite over federation doesn't break incremental /sync