Re: [w3ctag/design-reviews] Deprecating `document.domain`. (#564)

> Why can the existing `Origin-Agent-Cluster` header not be used?

If we did that, we'd basically end up inverting the default clustering algorithm, and asking developers to opt-out by setting `Origin-Agent-Cluster: ?0`? I think it's a reasonable alternative to consider, as it matches the goal we have from the browser's perspective.

The plan we've been running with has been to carve off the specific web APIs that developers may be depending upon, and give them targeted messaging around those options. A `document-domain` policy feature seemed like a reasonably well-targeted option whose impact developers could understand easily. But, since Chromium is [in the process](https://groups.google.com/a/chromium.org/g/blink-dev/c/nhmP8A61xk8/m/hyC0ntrMFAAJ) of carving off the only other remaining sticking point (cross-origin module sharing), perhaps it does make sense to jump right to the end.

Practically, that might be a problem for Chromium's implementation, as I think the process allocation heuristics are currently tuned for `Origin-Agent-Cluster` hints being rare (especially on mobile); I can imagine performance impacts in the short-term if we enabled it across the board. It would be more practical in the short-term to separate the `document.domain` question from the process allocation question so that we can handle the one and then the other. But philosophically, I can understand the appeal of skipping the document policy in favor of the existing header.

I'd appreciate the TAG's feedback on the developer messaging, as well as input from folks at Google who have been working with developers on this (@lutzvahl and @agektmr, I think?).

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/w3ctag/design-reviews/issues/564#issuecomment-917973757