[SOLVED] Is it possible to set a global dispatcher for the built-in `fetch()` in Node?

Is it possible to set a global dispatcher for the built-in `fetch()` in Node?

You can pass a dispatcher to fetch() in Node:

import { Agent } from 'undici';

const response = await fetch(url, {
  dispatcher: new Agent(/* ... */),
});

And you can set a global dispatcher if you're using undici on its own:

import { Agent, fetch, setGlobalDispatcher } from 'undici';

setGlobalDispatcher(new Agent(/* ... */));
const response = await fetch(url);

But how would I go about obtaining the setGlobalDispatcher() function that's bound to the global dispatcher the built-in instance of fetch() that Node 18+ uses? Surely using a setGlobalDispatcher() function from a version of undici that I install will not be the same one.

Solution

According to this discussion: https://github.com/nodejs/undici/discussions/2167#discussioncomment-6239415 it can be achieved by the following:

globalThis[Symbol.for('undici.globalDispatcher.1')] = yourDispatcher;

However I agree with Mike Pomax that this isn't a great idea. A better design would be to wrap fetch with your own local library, that overrides the dispatcher as you please. Then import that to use.