Invalidate lazyLoadCache if we're doing an initial sync (#2623)

* Bypass lazyLoadCache if we're doing an initial sync

* Make the linter happy again?

* Revert "Make the linter happy again?"

This reverts commit 52a5691ba3c17c05698bcc6a13092090f27ace63.

* Try that again

* Invalidate LazyLoadCache on initial syncs

* Remove unneeded check

* Add TODO

* Rename Invalite -> InvalidateLazyLoadedUser

* Thanks IDE

3 files changed, 19 insertions, 4 deletions

diff --git a/syncapi/routing/messages.go b/syncapi/routing/messages.go
index 990ca55b..b4c9a542 100644
--- a/syncapi/routing/messages.go
+++ b/syncapi/routing/messages.go
@@ -20,6 +20,10 @@ import (
 	"net/http"
 	"sort"
 
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
+	"github.com/sirupsen/logrus"
+
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	"github.com/matrix-org/dendrite/internal/caching"
 	"github.com/matrix-org/dendrite/roomserver/api"
@@ -28,9 +32,6 @@ import (
 	"github.com/matrix-org/dendrite/syncapi/sync"
 	"github.com/matrix-org/dendrite/syncapi/types"
 	userapi "github.com/matrix-org/dendrite/userapi/api"
-	"github.com/matrix-org/gomatrixserverlib"
-	"github.com/matrix-org/util"
-	"github.com/sirupsen/logrus"
 )
 
 type messagesReq struct {
@@ -262,7 +263,7 @@ func (m *messagesResp) applyLazyLoadMembers(
 		}
 	}
 	for _, evt := range membershipToUser {
-		m.State = append(m.State, gomatrixserverlib.HeaderedToClientEvent(evt, gomatrixserverlib.FormatSync))
+		m.State = append(m.State, gomatrixserverlib.HeaderedToClientEvent(evt, gomatrixserverlib.FormatAll))
 	}
 }
 
diff --git a/syncapi/streams/stream_pdu.go b/syncapi/streams/stream_pdu.go
index 1003208f..1ad3adc4 100644
--- a/syncapi/streams/stream_pdu.go
+++ b/syncapi/streams/stream_pdu.go
@@ -12,9 +12,12 @@ import (
 	roomserverAPI "github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/syncapi/types"
 	userapi "github.com/matrix-org/dendrite/userapi/api"
+
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/tidwall/gjson"
 	"go.uber.org/atomic"
+
+	"github.com/matrix-org/dendrite/syncapi/notifier"
 )
 
 // The max number of per-room goroutines to have running.
@@ -34,6 +37,7 @@ type PDUStreamProvider struct {
 	// userID+deviceID -> lazy loading cache
 	lazyLoadCache caching.LazyLoadCache
 	rsAPI         roomserverAPI.SyncRoomserverAPI
+	notifier      *notifier.Notifier
 }
 
 func (p *PDUStreamProvider) worker() {
@@ -100,6 +104,15 @@ func (p *PDUStreamProvider) CompleteSync(
 		req.Log.WithError(err).Error("unable to update event filter with ignored users")
 	}
 
+	// Invalidate the lazyLoadCache, otherwise we end up with missing displaynames/avatars
+	// TODO: This might be inefficient, when joined to many and/or large rooms.
+	for _, roomID := range joinedRoomIDs {
+		joinedUsers := p.notifier.JoinedUsers(roomID)
+		for _, sharedUser := range joinedUsers {
+			p.lazyLoadCache.InvalidateLazyLoadedUser(req.Device, roomID, sharedUser)
+		}
+	}
+
 	// Build up a /sync response. Add joined rooms.
 	var reqMutex sync.Mutex
 	var reqWaitGroup sync.WaitGroup
diff --git a/syncapi/streams/streams.go b/syncapi/streams/streams.go
index 1ca4ee8c..dbc053bd 100644
--- a/syncapi/streams/streams.go
+++ b/syncapi/streams/streams.go
@@ -34,6 +34,7 @@ func NewSyncStreamProviders(
 			StreamProvider: StreamProvider{DB: d},
 			lazyLoadCache:  lazyLoadCache,
 			rsAPI:          rsAPI,
+			notifier:       notifier,
 		},
 		TypingStreamProvider: &TypingStreamProvider{
 			StreamProvider: StreamProvider{DB: d},