Why at my service worker range header is not being sent?

Question

Hi I have simple service worker, but my Range header is not being send even thought i can log it on request object.

self.addEventListener('fetch', async function(event) {
    if (event.request.headers.get("range")) {
      const response = await fetch(event.request.clone());

      return  event.respondWith(this.getPartialResponse(event.request, response));
    }

    return  event.respondWith(fetch(event.request));
}

async getPartialResponse(req, res) {
  const pos = Number(/^bytes\=(\d+)\-$/g.exec(req.headers.get("range"))[1]);
  const ab = await res.arrayBuffer();
  const headers = new Headers(res.headers);

  headers.append("Content-Range", `bytes ${pos}-${ab.byteLength - 1}/${ab.byteLength}`);
  headers.append("Content-Length", ab.byteLength - pos + 1);

  return new Response(ab.slice(pos), {
    status: 206,
    statusText: "Partial Content",
    headers
  });
}

Here you can see request one catched by service worker and the second one send to the api where you can notice the Range header is missing. Why ? My browser: Chrome/59.0.3071.104

Answer 1

caveat, I don't know what a range header is, so bear with me. I know some headers are not available to the service worker for security reasons. Basically you cannot tamper with the request and response. For example you do not have access to Cache-Control in response objects from 3rd party domains, that way you cannot adjust the HTTP caching logic. This might be your issue, but I can't say for sure. Look up rules concerning opaque request & responses.