Excessive NodeError creation while using AbortSignal.timeout

[slagiewka]

Bug Description

I'm not sure if this is something that undici should handle or something that can be patched in node.

We're using a timeout signal in every request made by fetch. Since the service is working as an API gateway, we do this A LOT.

It seems like this check is running unnecessary: AbortSignal has [kMaxEventTargetListeners] set to 0.

So the getMaxListeners does not check considers the AbortSignal to be an EventTarget because the condition:

else if (emitterOrTarget?.[kMaxEventTargetListeners])

evaluates to 0.

Should this not be surrounded by try-catch like is in undici this would result in:

TypeError [ERR_INVALID_ARG_TYPE]: The "emitter" argument must be an instance of EventEmitter or EventTarget. Received an instance of AbortSignal

Reproducible By

This should be as simple as running

import {fetch} from 'undici';

await fetch('https://nodejs.org', {signal: AbortSignal.timeout(1_000));

Expected Behavior

Less time spent creating invisible, unimportant errors 🙂

Logs & Screenshots

The offending tree

getMaxListeners

Expensive NodeError

Callsite

Environment

Node v22.13.1 (running inside Alpine on Docker)
Using undici v7.

Additional context

I see that there was this issue about the error being visible: nodejs/node#46823
Now it's just silent, but expensive.

[KhafraDev]

It seems like this check is running unnecessary: AbortSignal has [kMaxEventTargetListeners] set to 0.

This was changed a month ago and is currently only available in node v22.13.0+ and v23.5.0+. If it could be backported to v20, we can consider removing it.

So the getMaxListeners does not check considers the AbortSignal to be an EventTarget because the condition:

This looks like a bug in node. The condition should be changed to else if (typeof emitterOrTarget?.[kMaxEventTargetListeners] === 'number') or similar.

[slagiewka]

This was changed a month ago and is currently only available in node v22.13.0+ and v23.5.0+.

Correct. I just found that out right now, as I tried to reproduce the issue inside Fedora 41 which has 22.11. No issue there.

This looks like a bug in node. The condition should be changed to else if (typeof emitterOrTarget?.[kMaxEventTargetListeners] === 'number') or similar.

I agree. Seems like an honest mistake, since AbortSignal IS an EventTarget and it functions properly with setMaxListeners. I see no reason why it wouldn't pass that check and return the symbol.

[KhafraDev]

I submitted a PR to fix it, where I realized I added getEventListeners and therefore this bug. Whoops...