Cross Domain Web Workers

Question

I am aware that this question might be considered duplicate, but it is a new technology and I can not find a recent confirmation of my findings. I also think it potentially useful to have all the error messages in one place (feel free to add any other browsers).

trying to loads a worker script from another domain:

new Worker('http://otherdomain.co/worker.js');

I have set headers (using ModHeader Chrome Extension) to:

Access-Control-Allow-Methods:* Access-Control-Allow-Origin:*

But in Chrome I get:

Uncaught SecurityError: Failed to construct 'Worker': Script at 'http:otherdomain.co/worker.js' cannot be accessed from origin

Safari give me:

[Error] SecurityError: DOM Exception 18: An attempt was made to break through the security policy of the user agent

Firefox gives me:

SecurityError: The operation is insecure.

Is it still that this is not something we can do? If so, what is considered the best practise work around?

Answer 1

You are not allowed to create cross-domain web workers.

Note : The URI passed as parameter of the Worker constructor must obey the same-origin policy . There is currently disagreement among browsers vendors on what URIs are of the same-origin; Gecko 10.0 (Firefox 10.0 / Thunderbird 10.0 / SeaMonkey 2.7) and later do allow data URIs and Internet Explorer 10 does not allow Blob URIs as a valid script for workers.

Source: https://developer.mozilla.org/en/docs/Web/Guide/Performance/Using_web_workers

One workaround that I can think of is to create a server-side script to load the required remote JS file, and supply it to the browser from your domain.

Eg: You supply url to :

http://YOUR_DOMAIN/getRemoteJS.php

This PHP file will request the remote file on the server side, and echo it as the response, and set mime-type to application/javascript.

I have not personally tried this workaround, but you can perhaps look into it.

Good Luck!

Answer 2

There's a way to run cross-origin workers with:

• fetching JS code of the worker
• run worker from data: string or blob:

Working solution: https://github.com/CezaryDanielNowak/CrossOriginWorker

Answer 3

I know it's a little late now, but is this what you're looking for?

"Creates a url for the specified blob that can be passed to methods that expect a url. When done with the returned url, call revokeObjectURL() to free the resources associated with the created url."

This method easily allows you to create a Worker using a local script instead of a remote url.