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Unstable UDP listener does not provide reusePort/SO_REUSEPORT option, all traffic on one thread #36858
Description
As described. The Deno.listenDatagram API does not provide the SO_REUSEPORT socket option.
Looking through some other issues and code comments shows that it isn't available due to cross-platform compatibility. I think it would be convenient to have this available, at least on Linux. I'm not so sure about how Deno handles I/OCP on Windows, though it would also be a nice-to-have. Deno.TcpListenOptions already implements reusePort.
const workerId = crypto.randomUUID();
const listener = Deno.listenDatagram({
transport: "udp",
port: 3000,
hostname: "127.0.0.1",
reusePort: true
}); // across several worker threads
const cb = (d: Uint8Array<ArrayBufferLike>, a: Deno.Addr) => {
console.log(`(${workerId}) ${d.byteLength} from ${a.hostname}:${a.port}`);
}
const loop = () => {
listener.receive().then(([d, a]) => cb(d, a)).finally(loop);
};
loop();
Activity
[-]Unstable UDP listener does not provide `reusePort`/`SO_REUSEPORT` option[/-][+]Unstable UDP listener does not provide `reusePort`/`SO_REUSEPORT` option, all traffic on one thread[/+]ZombieB1309 commentedon Sep 17, 2026
Looking at the source more closely.
set_reuse_portis set explicitly but I'm seeing all traffic go to one thread.Tiancheng-Xu commentedon Sep 17, 2026
I can investigate the missing
reusePort/SO_REUSEPORToption for unstable UDP listeners. I will reproduce the current listener behavior, trace the platform-specific socket setup, and add focused regression coverage with the smallest compatible change if confirmed. I will report the validation results in the PR.ZombieB1309 commentedon Sep 18, 2026
Update: I was able to compile with
set_reuse_portset withoutset_reuse_addrinnet_listen_udpand it seems to work. It now seems likeset_reuse_addris causing the thread exclusivity.