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Merged
merged 4 commits into from
Oct 21, 2025
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Ensure FFI events are processed sequentially #547

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8fc202f
Ensure FFI events are processed sequentially
lukasIO Oct 8, 2025
0d4dcb4
naming
lukasIO Oct 8, 2025
e9169b5
remove setImmediate
lukasIO Oct 8, 2025
15a2fbc
Create healthy-cherries-allow.md
lukasIO Oct 14, 2025
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5 changes: 5 additions & 0 deletions .changeset/healthy-cherries-allow.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@livekit/rtc-node": patch
---

Ensure FFI events are processed sequentially
78 changes: 48 additions & 30 deletions packages/livekit-rtc/src/participant.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -155,8 +155,15 @@ export type DataPublishOptions = {
export class LocalParticipant extends Participant {
private rpcHandlers: Map<string, (data: RpcInvocationData) => Promise<string>> = new Map();

private roomEventLock: Mutex;

trackPublications: Map<string, LocalTrackPublication> = new Map();

constructor(info: OwnedParticipant, roomEventLock: Mutex) {
super(info);
this.roomEventLock = roomEventLock;
}

async publishData(data: Uint8Array, options: DataPublishOptions) {
const req = new PublishDataRequest({
localParticipantHandle: this.ffi_handle.handle,
Expand Down Expand Up @@ -655,51 +662,62 @@ export class LocalParticipant extends Participant {
options: options,
});

const unlock = await this.roomEventLock.lock();

const res = FfiClient.instance.request<PublishTrackResponse>({
message: { case: 'publishTrack', value: req },
});

const cb = await FfiClient.instance.waitFor<PublishTrackCallback>((ev) => {
return ev.message.case == 'publishTrack' && ev.message.value.asyncId == res.asyncId;
});
try {
const cb = await FfiClient.instance.waitFor<PublishTrackCallback>((ev) => {
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thought(non-blocking)
curiously, does FfiClient.instance.request guarantee that it will trigger a PublishTrackCallback later ?

There is no need to change it now, but just an idea, I wonder if it makes sense to do things like

  1. prepare a waiter
  2. roomEventLock.lock()
  3. FfiClient.instance.request
  4. waiter.setAsyncId(res.asyncId)
  5. waiter will wait with some timeout, like await waiter.wait({ timeoutMs: 50 }); // not sure if that will bring more flakiness or less here.

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curiously, does FfiClient.instance.request guarantee that it will trigger a PublishTrackCallback later ?

I think so, yes. Not sure what the actual guarantees are though or rather how they are enforced.

return ev.message.case == 'publishTrack' && ev.message.value.asyncId == res.asyncId;
});

switch (cb.message.case) {
case 'publication':
const track_publication = new LocalTrackPublication(cb.message.value!);
track_publication.track = track;
this.trackPublications.set(track_publication.sid!, track_publication);
switch (cb.message.case) {
case 'publication':
const track_publication = new LocalTrackPublication(cb.message.value!);
track_publication.track = track;
this.trackPublications.set(track_publication.sid!, track_publication);

return track_publication;
case 'error':
default:
throw new Error(cb.message.value);
return track_publication;
case 'error':
default:
throw new Error(cb.message.value);
}
} finally {
unlock();
}
}

async unpublishTrack(trackSid: string, stopOnUnpublish?: boolean) {
const req = new UnpublishTrackRequest({
localParticipantHandle: this.ffi_handle.handle,
trackSid: trackSid,
stopOnUnpublish: stopOnUnpublish ?? true,
});
const unlock = await this.roomEventLock.lock();
try {
const req = new UnpublishTrackRequest({
localParticipantHandle: this.ffi_handle.handle,
trackSid: trackSid,
stopOnUnpublish: stopOnUnpublish ?? true,
});

const res = FfiClient.instance.request<UnpublishTrackResponse>({
message: { case: 'unpublishTrack', value: req },
});
const res = FfiClient.instance.request<UnpublishTrackResponse>({
message: { case: 'unpublishTrack', value: req },
});

const cb = await FfiClient.instance.waitFor<UnpublishTrackCallback>((ev) => {
return ev.message.case == 'unpublishTrack' && ev.message.value.asyncId == res.asyncId;
});
const cb = await FfiClient.instance.waitFor<UnpublishTrackCallback>((ev) => {
return ev.message.case == 'unpublishTrack' && ev.message.value.asyncId == res.asyncId;
});

if (cb.error) {
throw new Error(cb.error);
}
if (cb.error) {
throw new Error(cb.error);
}

const pub = this.trackPublications.get(trackSid);
if (pub) {
pub.track = undefined;
const pub = this.trackPublications.get(trackSid);
if (pub) {
pub.track = undefined;
}
this.trackPublications.delete(trackSid);
} finally {
unlock();
}
this.trackPublications.delete(trackSid);
}

/**
Expand Down
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