Modify request before calling other worker on specific URL Cloudflare #workers-help

Modify request before calling other worker on spec...

McSneaky

01/08/2024, 2:28 PM

Is it possible to modify request before passing it to binding? Let's say I have code like this on top level worker that sits on https://example.com/edge/backporter

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ts
import { Router } from 'itty-router';
const router = Router();

router.get('/edge/backporter', async (request) => {
  request.query = '?foobar' // modify request
  // Set URL to specific URL in other worker
  request.url = '/edge/v1' // Error, cannot set read-only property
  return env.BINDING.fetch(request);
}

And on

BINDING

worker I have router that responds to certain URL only https://example.com/edge/v1

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ts
import { Router } from 'itty-router';
const router = Router();

router.get('/edge/v1', async (request) => { ... }

I'd like to make sure request from first worker ends up in

/edge/v1

, but it never does, since I can't change request URL, nor can I

request.clone()

, since then URL would match

/edge/backporter

and not

/edge/v1

Is anything like this possible?

kian

01/08/2024, 2:29 PM

env.BINDING.fetch("http://service/edge/v1", request)

McSneaky

01/08/2024, 2:30 PM

Cool stuff! Works perfectly!

McSneaky

01/08/2024, 2:30 PM

McSneaky

01/08/2024, 2:31 PM

Couldn't find it anywhere 😐

kian

01/08/2024, 2:50 PM

The

fetch()

API looks like this:

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ts
fetch(
  input: RequestInfo,
  init?: RequestInit<RequestInitCfProperties>
): Promise<Response>;

RequestInfo

is either a Request, a string or a URL. In this case, we pass a string (

http://service/edge/v1

) and pass the original Request to the optional

init

property to carry over everything in

RequestInit

, like `method`/`headers`/`body`/`cf`.

kian

01/08/2024, 2:50 PM

You could also do...

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js
const url = new URL(request.url);
url.pathname = "/edge/v1"

await fetch(url, request);

etc

McSneaky

01/08/2024, 2:53 PM

Yeah, I tried to pass full URL, that didn't work, then found about service / worker binding, but all doc examples were just passing the same request or

request.clone()

Which made me think it's not possible to modify the request

McSneaky

01/08/2024, 2:54 PM

Replacing base URL (example.com) with service name is exactly the thing I was looking for 😋

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