Merge pull request #3610 from matrix-org/jryans/alias-cache

Improve room switching performance with alias cache

src/RoomAliasCache.js

@@ -0,0 +1,35 @@
+/*
+Copyright 2019 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.
+*/
+
+/**
+ * This is meant to be a cache of room alias to room ID so that moving between
+ * rooms happens smoothly (for example using browser back / forward buttons).
+ *
+ * For the moment, it's in memory only and so only applies for the current
+ * session for simplicity, but could be extended further in the future.
+ *
+ * A similar thing could also be achieved via `pushState` with a state object,
+ * but keeping it separate like this seems easier in case we do want to extend.
+ */
+const aliasToIDMap = new Map();
+
+export function storeRoomAliasInCache(alias, id) {
+    aliasToIDMap.set(alias, id);
+}
+
+export function getCachedRoomIDForAlias(alias) {
+    return aliasToIDMap.get(alias);
+}

src/components/structures/MatrixChat.js

@@ -60,6 +60,7 @@ import AutoDiscoveryUtils from "../../utils/AutoDiscoveryUtils";
 import DMRoomMap from '../../utils/DMRoomMap';
 import { countRoomsWithNotif } from '../../RoomNotifs';
 import { setTheme } from "../../theme";
+import { storeRoomAliasInCache } from '../../RoomAliasCache';
 
 // Disable warnings for now: we use deprecated bluebird functions
 // and need to migrate, but they spam the console with warnings.
@@ -866,7 +867,12 @@ export default createReactClass({
             const room = MatrixClientPeg.get().getRoom(roomInfo.room_id);
             if (room) {
                 const theAlias = Rooms.getDisplayAliasForRoom(room);
-                if (theAlias) presentedId = theAlias;
+                if (theAlias) {
+                    presentedId = theAlias;
+                    // Store display alias of the presented room in cache to speed future
+                    // navigation.
+                    storeRoomAliasInCache(theAlias, room.roomId);
+                }
 
                 // Store this as the ID of the last room accessed. This is so that we can
                 // persist which room is being stored across refreshes and browser quits.

src/stores/RoomViewStore.js

@@ -20,6 +20,7 @@ import MatrixClientPeg from '../MatrixClientPeg';
 import sdk from '../index';
 import Modal from '../Modal';
 import { _t } from '../languageHandler';
+import { getCachedRoomIDForAlias, storeRoomAliasInCache } from '../RoomAliasCache';
 
 const INITIAL_STATE = {
     // Whether we're joining the currently viewed room (see isJoining())
@@ -137,7 +138,7 @@ class RoomViewStore extends Store {
         }
     }
 
-    _viewRoom(payload) {
+    async _viewRoom(payload) {
         if (payload.room_id) {
             const newState = {
                 roomId: payload.room_id,
@@ -176,7 +177,12 @@ class RoomViewStore extends Store {
                 this._joinRoom(payload);
             }
         } else if (payload.room_alias) {
-            // Resolve the alias and then do a second dispatch with the room ID acquired
+            // Try the room alias to room ID navigation cache first to avoid
+            // blocking room navigation on the homeserver.
+            let roomId = getCachedRoomIDForAlias(payload.room_alias);
+            if (!roomId) {
+                // Room alias cache miss, so let's ask the homeserver. Resolve the alias
+                // and then do a second dispatch with the room ID acquired.
                 this._setState({
                     roomId: null,
                     initialEventId: null,
@@ -186,25 +192,30 @@ class RoomViewStore extends Store {
                     roomLoading: true,
                     roomLoadError: null,
                 });
-            MatrixClientPeg.get().getRoomIdForAlias(payload.room_alias).done(
-            (result) => {
+                try {
+                    const result = await MatrixClientPeg.get().getRoomIdForAlias(payload.room_alias);
+                    storeRoomAliasInCache(payload.room_alias, result.room_id);
+                    roomId = result.room_id;
+                } catch (err) {
+                    dis.dispatch({
+                        action: 'view_room_error',
+                        room_id: null,
+                        room_alias: payload.room_alias,
+                        err,
+                    });
+                    return;
+                }
+            }
+
             dis.dispatch({
                 action: 'view_room',
-                    room_id: result.room_id,
+                room_id: roomId,
                 event_id: payload.event_id,
                 highlighted: payload.highlighted,
                 room_alias: payload.room_alias,
                 auto_join: payload.auto_join,
                 oob_data: payload.oob_data,
             });
-            }, (err) => {
-                dis.dispatch({
-                    action: 'view_room_error',
-                    room_id: null,
-                    room_alias: payload.room_alias,
-                    err: err,
-                });
-            });
         }
     }