Cloudflare Developers•5mo ago

Modify request before calling other worker on specific URL

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

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);
}

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

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

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

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?

4 Replies

kian•5mo ago

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

McSneaky•5mo ago

Cool stuff! Works perfectly! <:cavai_hearts:908519873188098118> Couldn't find it anywhere 😐

kian•5mo ago

The fetch() API looks like this:

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

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. You could also do...

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

await fetch(url, request);

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

await fetch(url, request);

etc

McSneaky•5mo ago

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

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Modify request before calling other worker on specific URL