Cloudflare Developers•7mo ago

Worker uploaded via API: fetch vs service worker

I have been upoading workers via the api using this API: https://developers.cloudflare.com/api/operations/worker-script-upload-worker-module There are 2 types of runtime APIs when using workers, I think they are referred to as "fetch" and "service worker". What I mean is that I can write my worker like this:

export default {
    async fetch(request, env, ctx) {
        return new Response('Hello World!');
    },
};

export default {
    async fetch(request, env, ctx) {
        return new Response('Hello World!');
    },
};

Or:

addEventListener("fetch", (event) => event.respondWith(new Response("hello")));

addEventListener("fetch", (event) => event.respondWith(new Response("hello")));

I think the first one is preferred (fetch). However, when I upload to the API, only the the other one works (service worker). I'm therefore assuming that the service worker API is what is actually being run, it is a lower level thing. The fetch functionality is added by wrangler when it builds. So when uploading via the API we have to use the service worker API. Which is totally ok, just want to check if this is the case?

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1 Reply

DaniFoldi•7mo ago

Hi, I share your confusion around this topic, there are about half a dozen different way to upload a worker, and the best part is that the upload worker module endpoint only accepts "service worker" syntax (btw the other one with export default is usually referred to as "module worker" in the docs. The runtime can understand both forms natively, you just need to use a different endpoint for uploading module workers: https://developers.cloudflare.com/api/operations/worker-script-put-content - hint: you do not need to provide either of the headers shown in the api docs, if you include a json part called metadata in the request body.

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Worker uploaded via API: fetch vs service worker