I’ve forked off ring.middleware.multipart-params into a new library called ring.middleware.upload-progress
It’s a bit rough-and-ready for now, and it uses the session to store the shared state about current uploads, which is probably not the best way to go about it – I’m thinking about introducing a new lower-level mechanism for low-memory shared state based on clojure’s STM tools, since this kind of thing is interesting for more than just uploads – but it does work as long as you’re not doing anything too fancy (if you’re worried, you can use a separate session store just for this info).
For the interested: the code is at github.
I’ve got some working “upload progress bar” javascript and routing code too, but it’s not in this project, so for now, you’ll have to roll your own.
I’ll get a clojars release done as soon as I’m satisfied this stuff is usable. Probably in the next few days.