Merge pull request #3854 from element-hq/valere/fix_race_connection_fails

Fix a race connection causing the joiner to never publish media to the call

playwright/widget/federation-oldest-membership-bug.spec.ts

@@ -0,0 +1,92 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { expect, test } from "@playwright/test";
+
+import { widgetTest } from "../fixtures/widget-user";
+import { HOST1, HOST2, TestHelpers } from "./test-helpers";
+
+widgetTest(
+  "Bug new joiner was not publishing on correct SFU",
+  async ({ addUser, browserName }) => {
+    test.skip(
+      browserName === "firefox",
+      "This is a bug in the old widget, not a browser problem.",
+    );
+
+    test.slow();
+
+    // 2 users in federation
+    const florian = await addUser("floriant", HOST1);
+    const timo = await addUser("timo", HOST2);
+
+    // Florian creates a room and invites Timo to it
+    const roomName = "Call Room";
+    await TestHelpers.createRoom(roomName, florian.page, [timo.mxId]);
+
+    // Timo joins the room
+    await TestHelpers.acceptRoomInvite(roomName, timo.page);
+
+    // Ensure we are in legacy mode (should be the default)
+    await TestHelpers.openWidgetSetEmbeddedElementCallRtcModeCloseWidget(
+      florian.page,
+      "legacy",
+    );
+    await TestHelpers.openWidgetSetEmbeddedElementCallRtcModeCloseWidget(
+      timo.page,
+      "legacy",
+    );
+
+    // Let timo create a call
+    await TestHelpers.startCallInCurrentRoom(timo.page, false);
+    await TestHelpers.joinCallFromLobby(timo.page);
+
+    // We want to simulate that the oldest membership authentication is way slower than
+    // the preffered auth.
+    // In this setup, timo advertised$ transport will be it's own, and the active will be the one from florian
+    await florian.page.route(
+      "**/matrix-rtc.othersite.m.localhost/livekit/jwt/**",
+      async (route) => {
+        await new Promise((resolve) => setTimeout(resolve, 2000)); // 5 second delay
+        await route.continue();
+      },
+    );
+
+    // Florian joins the call
+    await expect(florian.page.getByTestId("join-call-button")).toBeVisible();
+    await florian.page.getByTestId("join-call-button").click();
+    await TestHelpers.joinCallFromLobby(florian.page);
+
+    await florian.page.waitForTimeout(3000);
+    await timo.page.waitForTimeout(3000);
+
+    // We should see 2 video tiles everywhere now
+    for (const user of [timo, florian]) {
+      const frame = user.page
+        .locator('iframe[title="Element Call"]')
+        .contentFrame();
+      await expect(frame.getByTestId("videoTile")).toHaveCount(2);
+
+      // No one should be waiting for media
+      await expect(frame.getByText("Waiting for media...")).not.toBeVisible();
+
+      // There should be 2 video elements, visible and autoplaying
+      const videoElements = await frame.locator("video").all();
+      expect(videoElements.length).toBe(2);
+
+      const blockDisplayCount = await frame
+        .locator("video")
+        .evaluateAll(
+          (videos: Element[]) =>
+            videos.filter(
+              (v: Element) => window.getComputedStyle(v).display === "block",
+            ).length,
+        );
+      expect(blockDisplayCount).toBe(2);
+    }
+  },
+);

src/state/CallViewModel/CallViewModel.ts

@@ -546,9 +546,7 @@ export function createCallViewModel$(
     },
     connectionManager,
     matrixRTCSession,
-    localTransport$: scope.behavior(
+    localTransport$,
-      localTransport$.pipe(switchMap((t) => t.advertised$)),
-    ),
     logger: logger.getChild(`[${Date.now()}]`),
   });
 

src/state/CallViewModel/localMember/LocalMember.test.ts

@@ -33,13 +33,20 @@ import {
   PublishState,
   TrackState,
 } from "./LocalMember";
-import { MatrixRTCTransportMissingError } from "../../../utils/errors";
+import {
+  FailToGetOpenIdToken,
+  MatrixRTCTransportMissingError,
+} from "../../../utils/errors";
 import { Epoch, ObservableScope } from "../../ObservableScope";
 import { constant } from "../../Behavior";
 import { ConnectionManagerData } from "../remoteMembers/ConnectionManager";
 import { ConnectionState, type Connection } from "../remoteMembers/Connection";
 import { type Publisher } from "./Publisher";
 import { initializeWidget } from "../../../widget";
+import {
+  type LocalTransport,
+  type LocalTransportWithSFUConfig,
+} from "./LocalTransport";
 
 initializeWidget();
 
@@ -214,7 +221,7 @@ describe("LocalMembership", () => {
   };
 
   it("throws error on missing RTC config error", () => {
-    withTestScheduler(({ scope, hot, expectObservable }) => {
+    withTestScheduler(({ scope, hot, behavior, expectObservable }) => {
       const localTransport$ = scope.behavior<null | LivekitTransportConfig>(
         hot("1ms #", {}, new MatrixRTCTransportMissingError("domain.com")),
         null,
@@ -230,11 +237,16 @@ describe("LocalMembership", () => {
         ),
       };
 
+      const aLocalTransport: LocalTransport = {
+        advertised$: localTransport$,
+        active$: behavior("a", { a: null }),
+      };
+
       const localMembership = createLocalMembership$({
         scope,
         ...defaultCreateLocalMemberValues,
         connectionManager: mockConnectionManager,
-        localTransport$,
+        localTransport$: behavior("a", { a: aLocalTransport }),
       });
       localMembership.requestJoinAndPublish();
 
@@ -245,10 +257,62 @@ describe("LocalMembership", () => {
     });
   });
 
+  it("Should not publish to active transport if advertised has errors", () => {
+    withTestScheduler(({ scope, hot, behavior, expectObservable }) => {
+      const advertised$ = scope.behavior<null | LivekitTransportConfig>(
+        hot("--#", {}, new FailToGetOpenIdToken(new Error("foo"))),
+        null,
+      );
+
+      // Populate a connection for active
+      const connectionManagerData = new ConnectionManagerData();
+      connectionManagerData.add(connectionTransportBConnected, []);
+      const mockConnectionManager = {
+        transports$: constant(new Epoch([bTransport])),
+        connectionManagerData$: constant(new Epoch(connectionManagerData)),
+      };
+
+      const aLocalTransport: LocalTransport = {
+        advertised$,
+        active$: behavior("a", { n: null, a: bTransportWithSFUConfig }),
+      };
+
+      defaultCreateLocalMemberValues.createPublisherFactory.mockImplementation(
+        () => {
+          return {} as unknown as Publisher;
+        },
+      );
+      const publisherFactory =
+        defaultCreateLocalMemberValues.createPublisherFactory as ReturnType<
+          typeof vi.fn
+        >;
+
+      const localMembership = createLocalMembership$({
+        scope,
+        ...defaultCreateLocalMemberValues,
+        connectionManager: mockConnectionManager,
+        localTransport$: behavior("a", { a: aLocalTransport }),
+      });
+      localMembership.requestJoinAndPublish();
+
+      expectObservable(localMembership.localMemberState$).toBe("n-e", {
+        n: TransportState.Waiting,
+        e: expect.toSatisfy((e) => e instanceof FailToGetOpenIdToken),
+      });
+
+      // Should not have created any publisher
+      expect(publisherFactory).toHaveBeenCalledTimes(0);
+    });
+  });
+
   it("logs if callIntent cannot be updated", async () => {
     const scope = new ObservableScope();
 
-    const localTransport$ = new BehaviorSubject(aTransport);
+    const aLocalTransport: LocalTransport = {
+      advertised$: new BehaviorSubject(aTransport),
+      active$: new BehaviorSubject(aTransportWithSFUConfig),
+    };
+
     const mockConnectionManager = {
       transports$: constant(new Epoch([])),
       connectionManagerData$: constant(new Epoch(new ConnectionManagerData())),
@@ -264,7 +328,7 @@ describe("LocalMembership", () => {
         leaveRoomSession: vi.fn(),
       },
       connectionManager: mockConnectionManager,
-      localTransport$,
+      localTransport$: new BehaviorSubject(aLocalTransport),
     });
     const expextedLog =
       "'not connected yet' while updating the call intent (this is expected on startup)";
@@ -279,10 +343,31 @@ describe("LocalMembership", () => {
   const aTransport = {
     livekit_service_url: "a",
   } as LivekitTransportConfig;
+
+  const aTransportWithSFUConfig = {
+    transport: aTransport,
+    sfuConfig: {
+      jwt: "foo",
+      livekitAlias: "bar",
+      livekitIdentity: "baz",
+      url: "bro",
+    },
+  } as LocalTransportWithSFUConfig;
+
   const bTransport = {
     livekit_service_url: "b",
   } as LivekitTransportConfig;
 
+  const bTransportWithSFUConfig = {
+    transport: bTransport,
+    sfuConfig: {
+      jwt: "foo2",
+      livekitAlias: "bar2",
+      livekitIdentity: "baz2",
+      url: "bro2",
+    },
+  } as LocalTransportWithSFUConfig;
+
   const connectionTransportAConnected = {
     livekitRoom: mockLivekitRoom({
       localParticipant: {
@@ -307,7 +392,11 @@ describe("LocalMembership", () => {
   it("recreates publisher if new connection is used, always unpublish and end tracks", async () => {
     const scope = new ObservableScope();
 
-    const localTransport$ = new BehaviorSubject(aTransport);
+    const activeTransport$ = new BehaviorSubject(aTransportWithSFUConfig);
+    const aLocalTransport: LocalTransport = {
+      advertised$: new BehaviorSubject(aTransport),
+      active$: activeTransport$,
+    };
 
     const publishers: Publisher[] = [];
     let seed = 0;
@@ -343,10 +432,13 @@ describe("LocalMembership", () => {
       connectionManager: {
         connectionManagerData$: constant(new Epoch(connectionManagerData)),
       },
-      localTransport$,
+      localTransport$: new BehaviorSubject(aLocalTransport),
     });
     await flushPromises();
-    localTransport$.next(bTransport);
+    activeTransport$.next({
+      ...aTransportWithSFUConfig,
+      transport: bTransport,
+    });
     await flushPromises();
 
     expect(publisherFactory).toHaveBeenCalledTimes(2);
@@ -368,8 +460,6 @@ describe("LocalMembership", () => {
   it("only start tracks if requested", async () => {
     const scope = new ObservableScope();
 
-    const localTransport$ = new BehaviorSubject(aTransport);
-
     const publishers: Publisher[] = [];
 
     const tracks$ = new BehaviorSubject<LocalTrack[]>([]);
@@ -396,6 +486,11 @@ describe("LocalMembership", () => {
         typeof vi.fn
       >;
 
+    const aLocalTransport: LocalTransport = {
+      advertised$: new BehaviorSubject(aTransport),
+      active$: new BehaviorSubject(aTransportWithSFUConfig),
+    };
+
     const connectionManagerData = new ConnectionManagerData();
     connectionManagerData.add(connectionTransportAConnected, []);
     // connectionManagerData.add(connectionTransportB, []);
@@ -405,7 +500,7 @@ describe("LocalMembership", () => {
       connectionManager: {
         connectionManagerData$: constant(new Epoch(connectionManagerData)),
       },
-      localTransport$,
+      localTransport$: new BehaviorSubject(aLocalTransport),
     });
     await flushPromises();
     expect(publisherFactory).toHaveBeenCalledOnce();
@@ -428,9 +523,15 @@ describe("LocalMembership", () => {
     const scope = new ObservableScope();
 
     const connectionManagerData = new ConnectionManagerData();
-    const localTransport$ = new BehaviorSubject<null | LivekitTransportConfig>(
+
-      null,
+    const activeTransport$ =
-    );
+      new BehaviorSubject<null | LocalTransportWithSFUConfig>(null);
+
+    const aLocalTransport: LocalTransport = {
+      advertised$: new BehaviorSubject(aTransport),
+      active$: activeTransport$,
+    };
+
     const connectionManagerData$ = new BehaviorSubject(
       new Epoch(connectionManagerData),
     );
@@ -470,14 +571,14 @@ describe("LocalMembership", () => {
       connectionManager: {
         connectionManagerData$,
       },
-      localTransport$,
+      localTransport$: new BehaviorSubject(aLocalTransport),
     });
 
     await flushPromises();
     expect(localMembership.localMemberState$.value).toStrictEqual(
       TransportState.Waiting,
     );
-    localTransport$.next(aTransport);
+    activeTransport$.next(aTransportWithSFUConfig);
     await flushPromises();
     expect(localMembership.localMemberState$.value).toStrictEqual({
       matrix: RTCMemberStatus.Connected,

src/state/CallViewModel/localMember/LocalMember.ts

@@ -62,6 +62,8 @@ import {
 } from "../remoteMembers/Connection.ts";
 import { type HomeserverConnected } from "./HomeserverConnected.ts";
 import { and$ } from "../../../utils/observable.ts";
+import { type LocalTransport } from "./LocalTransport.ts";
+import { areLivekitTransportsEqual } from "../remoteMembers/MatrixLivekitMembers.ts";
 
 export enum TransportState {
   /** Not even a transport is available to the LocalMembership */
@@ -127,7 +129,7 @@ interface Props {
   createPublisherFactory: (connection: Connection) => Publisher;
   joinMatrixRTC: (transport: LivekitTransportConfig) => void;
   homeserverConnected: HomeserverConnected;
-  localTransport$: Behavior<LivekitTransportConfig | null>;
+  localTransport$: Behavior<LocalTransport>;
   matrixRTCSession: Pick<
     MatrixRTCSession,
     "updateCallIntent" | "leaveRoomSession"
@@ -160,7 +162,7 @@ interface Props {
 export const createLocalMembership$ = ({
   scope,
   connectionManager,
-  localTransport$: localTransportCanThrow$,
+  localTransport$,
   homeserverConnected,
   createPublisherFactory,
   joinMatrixRTC,
@@ -205,23 +207,43 @@ export const createLocalMembership$ = ({
   const logger = parentLogger.getChild("[LocalMembership]");
   logger.debug(`Creating local membership..`);
 
+  // We consider error on the transport as fatal.
+  // Whether it is the active transport or the preferred transport.
+  const handleTransportError = (e: unknown): Observable<null> => {
+    let error: ElementCallError;
+    if (e instanceof ElementCallError) {
+      error = e;
+    } else {
+      error = new UnknownCallError(
+        e instanceof Error ? e : new Error("Unknown error from localTransport"),
+      );
+    }
+    setTransportError(error);
+    return of(null);
+  };
+
+  // This is the transport that we will advertise in our membership.
+  const advertisedTransport$ = localTransport$.pipe(
+    switchMap((lt) => lt.advertised$),
+    catchError(handleTransportError),
+    distinctUntilChanged(areLivekitTransportsEqual),
+  );
+
   // Unwrap the local transport and set the state of the LocalMembership to error in case the transport is an error.
-  const localTransport$ = scope.behavior(
+  const activeTransport$ = scope.behavior(
-    localTransportCanThrow$.pipe(
+    localTransport$.pipe(
-      catchError((e: unknown) => {
+      switchMap((lt) => {
-        let error: ElementCallError;
+        return combineLatest([lt.active$, lt.advertised$]).pipe(
-        if (e instanceof ElementCallError) {
+          map(([active, advertised]) => {
-          error = e;
+            // Our policy is to not publish to another transport if our prefered transport is miss-configured
-        } else {
+            if (advertised == null) return null;
-          error = new UnknownCallError(
+
-            e instanceof Error
+            return active?.transport ?? null;
-              ? e
+          }),
-              : new Error("Unknown error from localTransport"),
+        );
-          );
-        }
-        setTransportError(error);
-        return of(null);
       }),
+      catchError(handleTransportError),
+      distinctUntilChanged(areLivekitTransportsEqual),
     ),
   );
 
@@ -229,7 +251,7 @@ export const createLocalMembership$ = ({
   const localConnection$ = scope.behavior(
     combineLatest([
       connectionManager.connectionManagerData$,
-      localTransport$,
+      activeTransport$,
     ]).pipe(
       map(([{ value: connectionData }, localTransport]) => {
         if (localTransport === null) {
@@ -398,7 +420,7 @@ export const createLocalMembership$ = ({
   const mediaState$: Behavior<LocalMemberMediaState> = scope.behavior(
     combineLatest([
       localConnectionState$,
-      localTransport$,
+      activeTransport$,
       joinAndPublishRequested$,
       from(trackStartRequested.promise).pipe(
         map(() => true),
@@ -537,9 +559,11 @@ export const createLocalMembership$ = ({
       });
   });
 
-  // Keep matrix rtc session in sync with localTransport$, connectRequested$
+  // Keep matrix rtc session in sync with advertisedTransport$, connectRequested$
   scope.reconcile(
-    scope.behavior(combineLatest([localTransport$, joinAndPublishRequested$])),
+    scope.behavior(
+      combineLatest([advertisedTransport$, joinAndPublishRequested$]),
+    ),
     async ([transport, shouldConnect]) => {
       if (!transport) return;
       // if shouldConnect=false we will do the disconnect as the cleanup from the previous reconcile iteration.

src/state/CallViewModel/localMember/LocalTransport.ts

@@ -106,7 +106,7 @@ export function isLocalTransportWithSFUConfig(
   return "transport" in obj && "sfuConfig" in obj;
 }
 
-interface LocalTransport {
+export interface LocalTransport {
   /**
    * The transport to be advertised in our MatrixRTC membership. `null` when not
    * yet fetched/validated.