Skip to content

Fix: Main thread blocked for ~1s during WebRTC connection setup #834

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 2 commits into
base: develop
Choose a base branch
from
Open

Fix: Main thread blocked for ~1s during WebRTC connection setup #834

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
e98a8e1
fix: remove main thread blocking from WebRTC peer connection setup
sampepose Jun 7, 2025
322e4e4
Fix thread safety for RTCPeerConnection access
sampepose Jun 7, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
65 changes: 42 additions & 23 deletions Sources/StreamVideo/WebRTC/v2/PeerConnection/StreamRTCPeerConnection.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,9 @@ final class StreamRTCPeerConnection: StreamRTCPeerConnectionProtocol, @unchecked

/// A dispatch queue for handling peer connection operations.
let dispatchQueue = DispatchQueue(label: "io.getstream.peerconnection")

/// A dispatch queue for safely accessing `source`. RTCPeerConnection is not thread-safe.
private let connectionQueue = DispatchQueue(label: "io.getstream.peerconnection.connection")

/// A publisher for RTCPeerConnectionEvents.
lazy var publisher: AnyPublisher<RTCPeerConnectionEvent, Never> = delegatePublisher
Expand Down Expand Up @@ -72,7 +75,6 @@ final class StreamRTCPeerConnection: StreamRTCPeerConnectionProtocol, @unchecked
///
/// - Parameter sessionDescription: The RTCSessionDescription to set as the local description.
/// - Throws: An error if setting the local description fails.
@MainActor
func setLocalDescription(
_ sessionDescription: RTCSessionDescription
) async throws {
Expand All @@ -84,11 +86,14 @@ final class StreamRTCPeerConnection: StreamRTCPeerConnectionProtocol, @unchecked
return
}

source.setLocalDescription(sessionDescription) { error in
if let error = error {
continuation.resume(throwing: error)
} else {
continuation.resume(returning: ())
connectionQueue.async { [weak self] in
guard let self else { return }
source.setLocalDescription(sessionDescription) { error in
if let error = error {
continuation.resume(throwing: error)
} else {
continuation.resume(returning: ())
}
}
}
} as ()
Expand All @@ -98,7 +103,6 @@ final class StreamRTCPeerConnection: StreamRTCPeerConnectionProtocol, @unchecked
///
/// - Parameter sessionDescription: The RTCSessionDescription to set as the remote description.
/// - Throws: An error if setting the remote description fails.
@MainActor
func setRemoteDescription(
_ sessionDescription: RTCSessionDescription
) async throws {
Expand All @@ -110,12 +114,15 @@ final class StreamRTCPeerConnection: StreamRTCPeerConnectionProtocol, @unchecked
return
}

source.setRemoteDescription(sessionDescription) { error in
if let error = error {
continuation.resume(throwing: error)
} else {
self.subject.send(HasRemoteDescription(sessionDescription: sessionDescription))
continuation.resume(returning: ())
connectionQueue.async { [weak self] in
guard let self else { return }
source.setRemoteDescription(sessionDescription) { error in
if let error = error {
continuation.resume(throwing: error)
} else {
self.subject.send(HasRemoteDescription(sessionDescription: sessionDescription))
continuation.resume(returning: ())
}
}
}
} as ()
Expand Down Expand Up @@ -164,8 +171,13 @@ final class StreamRTCPeerConnection: StreamRTCPeerConnectionProtocol, @unchecked
with track: RTCMediaStreamTrack,
init transceiverInit: RTCRtpTransceiverInit
) -> RTCRtpTransceiver? {
let result = source.addTransceiver(with: track, init: transceiverInit)
storeTransceiver(result, trackType: trackType)
var result: RTCRtpTransceiver?
connectionQueue.sync {
result = source.addTransceiver(with: track, init: transceiverInit)
}
if let result {
storeTransceiver(result, trackType: trackType)
}
return result
}

Expand Down Expand Up @@ -197,18 +209,25 @@ final class StreamRTCPeerConnection: StreamRTCPeerConnectionProtocol, @unchecked

/// Restarts the ICE gathering process.
func restartIce() {
source.restartIce()
connectionQueue.async { [weak self] in
guard let self else { return }
self.source.restartIce()
}
}

/// Closes the peer connection.
func close() async {
Task { @MainActor in
/// It's very important to close any transceivers **before** we close the connection, to make
/// sure that access to `RTCVideoTrack` properties, will be handled correctly. Otherwise
/// if we try to access any property/method on a `RTCVideoTrack` instance whose
/// peerConnection has closed, we will get blocked on the Main Thread.
source.transceivers.forEach { $0.stopInternal() }
source.close()
await withCheckedContinuation { continuation in
connectionQueue.async { [weak self] in
guard let self else { return }
/// It's very important to close any transceivers **before** we close the connection, to make
/// sure that access to `RTCVideoTrack` properties, will be handled correctly. Otherwise
/// if we try to access any property/method on a `RTCVideoTrack` instance whose
/// peerConnection has closed, we will get blocked on the Main Thread.
self.source.transceivers.forEach { $0.stopInternal() }
self.source.close()
continuation.resume()
}
}
}

Expand Down