[Animats]

Yes. I've been saying this for some time. I call it "async contamination".

The async model assumes you spend most of your time waiting for your slow users to do something. (Why a web site, which is inherently stateless, should be doing that routinely is another issue.) I'm writing a metaverse client that has about 10-20 threads, many of them compute bound, running at different priorities. Works fine, but is totally different from the async model. Trying to keep async out of the networking has been difficult. I don't use "hyper" any more. I look at builds to see if "tokio" somehow got pulled in.

[estebank]

> Why a web site, which is inherently stateless, should be doing that routinely is another issue.

Because most web sites that would be doing this are not stateless? Any dynamic site will need to access a database, which means that the will be IO blocking, which means that given enough traffic the server will run out of available threads before being able to service the IO operations for all of these users. And because different parts of the website will likely have different DB load, you could easily cause a DoS by hitting an expensive endpoint repeatedly.

[losvedir]

Sorry, offtopic, but what do you mean by "metaverse client"? I've seen you mention this in a couple comments now and I'm intrigued. I don't imagine you mean something to do with Facebook, right?

[Animats]

A metaverse client is the program you run on your machine to talk to a metaverse server. There are several clients for Second Life, a client for VRchat, a client for SineSpace, and so forth. There are web-based clients running in a web browser in WebAssembly, such as the one for Decentraland. All of these are 3D graphics programs.

They're halfway between MMO game clients and web browsers. They have to do most of the things a game client does, but they don't have built-in assets or game logic. Rather than a giant download at install (the biggest AAA titles have passed 100GB), all content is coming from the servers as needed, as with a web browser. The client's job is to present a good-looking 3D world while busily downloading content as the user moves round the world. Hopefully before the user gets close enough to see it in detail. So they have the performance problems of a 3D game with the content-handling problems of a web browser.

An existing open source metaverse client is Firestorm, a viewer for Second Life and Open Simulator.[1] Here's the source code.[2] It's mostly single-thread and OpenGL based. I've made some small contributions to that.

I am working on a replacement, in Rust, with more concurrency. About 20-30 threads, not thousands. Thread priority matters. Top priority is refresh, keeping the frame rate up. Next is servicing the network and user inputs. Then comes content decompression and preprocessing for adding to the scene. Much of this is compute-bound. Rust is a huge help in keeping the concurrency straight. This would be a much harder job in C++.

As the metaverse moves from hype to implementation, this will be a bigger area of activity. Right now, it's a niche.

[1] https://www.firestormviewer.org/

[2] https://vcs.firestormviewer.org/phoenix-firestorm

[accountofme]

I've been calling it cancer, but I get down voted for that.