wg-async VS actix

I believe the solution mentioned in rust-lang/wg-async is the way to go: Add traits like AsyncWrite, AsyncRead, Executor/Runtime to the std so that tokio/async-std can implement them.

This is a consequence of runtimes relying on global variables that their core future types are dependent on. Creating abstractions to solve this problem is one of the main goals of the the async working group [0].

[0]: https://github.com/rust-lang/wg-async

Provided the futures you're selecting over are cancellation safe the plain loop over select! should be fine. Multiple channels in particular are safe to select over - if you have futures that aren't cancellation safe, you can just wrap them up in a task on the end of a channel and then select on that.

I'd like to be able to write runtime agnostic async libs.

You might be interested in taking a look at and potentially participating in the "Async Vision Document"[1] which is an exercise the team is going through to collect feedback about the current state of the ecosystem and what the pain points are, as well as a way to lay doing what the desired future state of async Rust should be[2]. The process is happening, as you would expect, in the open and there's still time to influence it[3] if your concerns aren't yet addressed or even mentioned[4].

[1]: https://rust-lang.github.io/wg-async-foundations/vision.html

[2]: https://blog.rust-lang.org/2021/03/18/async-vision-doc.html

[3]: https://github.com/rust-lang/wg-async-foundations/pulls

[4]: https://github.com/rust-lang/wg-async-foundations/issues

Thanks for the feedback. I posted this comment to a relevant github issue, fyi.

9. Actix

I think it's fairer to say the language got so much more powerful that there wasn't any point making actors a language feature when they can be built from existing orthogonal language features. You're probably looking for actix (not actix-web, just actix). There's also Lunatic built in Rust but supporting any actors compiled to WebAssembly.

Actix is an actor framework for developing concurrent applications built on top of the Tokio asynchronous runtime. It allows multiple actors to run on a single thread, but also allows actors to run on multiple threads via Arbiters. Actors can communicate with each other by sequentially exchanging typed messages.

I’ve seen frameworks for c++ (https://seastar.io/) and rust (https://github.com/actix/actix) which support what you’re describing out of the box.

The actix repository on github doesn't seem to be very active, and everyone seems to be focused on actix-web instead, is anyone out there using plain actix or any other actor-model implementation in Rust?

Rust is also another possibility: it's basically C++ but more modern with added features and safety. It can be tricky to write mathematical stuff in it, because you may not care too much about all the safety concerns Rust forces you to handle, but it can be useful to catch bugs ahead of times. Sadly, Rust seems to have no library for running programs on clusters of PCs, except maybe this one, which takes the Actor model implemented by Actix and runs it on a cluster. I don't know how tricky it is to use the Actor model for a scientific simulation, tho.

I'd just use Actix for that. Make your state an actor and make it a StreamHandler for each of these sources, and that's it - now you just implement the business logic for handling each message in the StreamHandler::handle methods.

However, this isn't even 50% of what's out there: Need raw parallel power (and maybe don't need an async runtime)? Checkout Rayon. Need simple Actors for concurrent processing? Checkout Actix. Need a larger Actor system for fault tolerance/CQRS messaging? Checkout Riker. Damn, I sound like a youtube advert 🤦 - For real though, this is the tip of the concurrency iceberg. There is so much more - and it's growing.