(In reply to comment #0)

A scalable system probably needs additional servers to handle the WebSockets
(or comet/long-poll style HTTP for compat with existing browsers),

We could write a client-side WebSockets layer that falls back to Comet if WebSockets aren't available. In fact, I'd be moderately surprised if something like that doesn't already exist.

but a basic
or more limited stub implementation could go into a standard PHP core that
would still be useful for many things on smaller sites.

...and again, support two entry points (WebSockets and Comet) on the server side.

There are many such libraries yes. :)

RFC: https://www.mediawiki.org/wiki/Requests_for_comment/Structured_data_push_notification_support_for_recent_changes

This isn't an actionable bug, and its dependencies don't really make sense (is all that going to happen and have a common interface?).

See also:

• (bug 14045) Set up an easy to parse recentchanges feed > [[wikitech:stream.wikimedia.org]] > [[wikitech:RCStream]]