Bug 25212 – Support constructing nested workers.

• Status: RESOLVED
• Resolution: FIXED
• Component: WebCore JavaScript

[Jian Li]

This is to make nested worker constructor work in JS bindings.

[Jian Li]

Created attachment 29502 [details]
Proposed Patch

[Alexey Proskuryakov]

We can't enable constructing nested workers in default build when they don't work nearly correctly. What changes does this depend upon?

[Jian Li]

(In reply to comment #2)
> We can't enable constructing nested workers in default build when they don't
> work nearly correctly. What changes does this depend upon?
> 

This change depends on the script loading work and termination work. I am currently working on the termination issue. I can have this change check in at last.

[Alexey Proskuryakov]

*** Bug 40288 has been marked as a duplicate of this bug. ***

[Jesper van den Ende]

Are there any plans for this?

[Peter B]

This is extremely useful to support parallelism

[Chris Dumez]

https://commits.webkit.org/254597@main

[Radar WebKit Bug Importer]

<rdar://problem/100079582>

[Peter B]

(In reply to Chris Dumez from comment #7)
> https://commits.webkit.org/254597@main

Chris! My hero! Do you know approximately when this commit will see the light of day?

[Lanny Heidbreder]

This appears to have already made it into Safari Technology Preview, at least.

When trying to use sqlite wasm on safari tech preview, "new Worker(new URL("sqlite3-opfs-async-proxy.js", import.meta.url));" inside a worker successfully creates a new worker, but it never starts.

[Jesper van den Ende]

Fwiw I managed to work around this challenge using the following polyfill:
https://github.com/dmihal/Subworkers

I have created a fork that adds support for module imports,
i.e: new Worker("file.js", { type: "module" });
https://github.com/jespertheend/Subworkers

Thanks for the polyfill, I tried it, but in subworkers.js the following message function is called:

self.postMessage({
  _subworker: true,
  cmd: 'newWorker',
  id: this.id,
  path: absPath
});

but never receiver anywhere. I guess, it should be received here:

var messageRecieved = function(event){
  if (event.data._subworker){
    cmds[event.data.cmd](event);
  }
};

[Jesper van den Ende]

When I first used the polyfill I wasn't working for me either. I believe it was because I was also using this module workers polyfill: https://gist.github.com/developit/220246bc99044af74a6680ce13284f59
and they were interfering with each other. I had to play around with the order of imports for a bit in order to fix it.

Though I'm not sure if you're running into the same issue here.

I'm not sure why, but I have to load the subworkers script in the head part of my index.html to work. It has to be there in the tests as well.
Anyway thanks :-).