Cloudflare Developers•4mo ago

Hi folks, I'm trying to speed run a

Hi folks, I'm trying to speed run a prototype with Workers on top of my existing local stack. Basically I want to simulate normal traffic serving, but only a subset of my traffic routes should go to Workers. Is there an off the shelf pattern I can use for doing this reverse proxy in front of my existing stack?

10 Replies

skgzOP•4mo ago

(Again, this is against my localhost stack. A prod-like env will be another beast.)

Hard@Work•4mo ago

Maybe within the Worker, have something like this?

export default {
  fetch(req, env, ctx) {
    const shouldSendToWorkers = Math.random() > 0.5;
    if(shouldSendToWorkers) {
      return actualWorkerCode(req, env, ctx);
    }
    return fetch(req);
  }
}

export default {
  fetch(req, env, ctx) {
    const shouldSendToWorkers = Math.random() > 0.5;
    if(shouldSendToWorkers) {
      return actualWorkerCode(req, env, ctx);
    }
    return fetch(req);
  }
}

skgzOP•4mo ago

Suppose I have my local stack running at the url: my-local.dev:1234 and I want the worker to handle: my-local.dev:1234/foo & my-local.dev:1234/bar And it should reverse proxy all other URLs. What would that config look like? Thanks btw!

Hard@Work•4mo ago

Are you using a Router already?

skgzOP•4mo ago

Where "my-local.dev" is just a localhost mapped DNS record No, brand new to Cloudflare! We currently use Cloudfront, and I'll be testing out a switch to cloudflare if this is successful.

Hard@Work•4mo ago

Ok, so the naive way is to just check the path of the incoming request directly, like

export default {
  fetch(req, env, ctx) {
    const { pathname } = new URL(req.url);
    if(pathname.startsWith("/foo") || pathname.startsWith("/bar")) {
      return actualWorkerCode(req, env, ctx);
    }
    return fetch(req);
  }
}

export default {
  fetch(req, env, ctx) {
    const { pathname } = new URL(req.url);
    if(pathname.startsWith("/foo") || pathname.startsWith("/bar")) {
      return actualWorkerCode(req, env, ctx);
    }
    return fetch(req);
  }
}

This works for one or two routes, but doesn't scale very well It also sends stuff like /foobar to your Worker, which may not be what you want

skgzOP•4mo ago

Where does the fetch call proxy to? Eg, if I have the worker listen on the 1234 port above, I'd need to map my local stack to 1235 (for example). Do I configure the upstream domain, or do I need to edit the req.url?

Hard@Work•4mo ago

I believe you can point it to a local service with --local-upstream

Hard@Work•4mo ago

https://developers.cloudflare.com/workers/wrangler/commands#dev

Cloudflare Docs

Commands - Wrangler · Cloudflare Workers docs

Create, develop, and deploy your Cloudflare Workers with Wrangler commands.

skgzOP•4mo ago

Thank you! I've got some stuff rolling. One more Q: If I want it to fetch some upstream data, how do I have it load that and cache it in the background? Eg, our build system generates a manifest that I'd like to cache locally (ideally I'd refresh this periodically).

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Hi folks, I'm trying to speed run a