WebRTC P2P connections are slow to open

[gpauloski]

Describe the problem.

I noticed on my WSL machine that the test suite suddenly became very slow sometime in the last month or so. Using --durations, every test using P2P was taking a multiple of 5 seconds (5, 10, or 20s in the worst case).

Inspecting the call stack for the slow part led me down this path:

RTCPeerConnection.setLocalDescription
RTCPeerConnection.__gather
RTCIceGatherer.gather
Connection.gather_candidates
Connection.get_component_candidates
server_reflective_candidate

The server_reflective_candidate() performs the STUN check as a coroutine with a 5s timeout determined by Connection.get_component_candidates(). I verified reducing this timeout reduces the WebRTC connection time.

Oddly, every other machine I tested on did not have this problem so it must be something related to the networking configuration of this one device. I also tried:

• Older versions of aiortc/aioice.
• Updating system packages.
• Using mirrored instead of NAT networking for WSL.
• Other STUN servers.

The issues seems to be lack of trickle ICE in aioice (related: pion/webrtc#460). aioice does not have trickle ICE support (aiortc/aioice#4) so I'm not sure there is much to be done about this, but I am documenting it here for reference and others that run into the issue.

This script reproduces the slowdown (but worked fine on other devices):

import asyncio
import aioice
from aiortc.rtcicetransport import connection_kwargs
from aiortc.rtcconfiguration import RTCIceServer

async def main():
    servers = [RTCIceServer("stun:stun.cloudflare.com:3478")]
    ice_kwargs = connection_kwargs(servers)
    connection = aioice.Connection(ice_controlling=False, **ice_kwargs)
    await connection.gather_candidates()

asyncio.run(main())

$ time python t.py
real    0m5.162s
user    0m0.152s
sys     0m0.000s

How did you install ProxyStore?

$ pip install proxystore

ProxyStore Version

0.7.0

Python Version

3.12

OS and Platform

Ubuntu