actix VS MIO

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.

Was playing around with mio (https://github.com/tokio-rs/mio) (not that mio itself is very important here!) and was trying to implement a simple something that I've done in java before: a Reactor that you can register ReactorClients with that will get callback whenever there are events on the corresponding socket etc.

How does it compare to mio?

TcpStream gets its wake behavior by delegating to the fd wakers. The Unix wakers have a few implementations, for different platforms. On Linux and Android, epoll is used.

The real implementation details of the I/O event queue is done in mio as u/hniksic pointed out, but that's more comparable with libuv which is certainly a huge part of the Node runtime. mio and libuv have a lot of similarities (at least they used to).

My example was "twice by one developer", not "twice across all indexed repos."

A spot check shows that quite a few in your link are used specifically to ensure correct handling of Rust multi-level breaks work syntax, like https://github.com/rust-lang/rust-analyzer/blob/master/crate... , https://github.com/rust-lang/rustfmt/blob/master/tests/sourc... , https://github.com/rust-lang/rust/blob/master/src/tools/rust... , https://github.com/rust-lang/rust/blob/master/src/tools/rust... and likely more.

Another is a translation of BASIC code to Rust, using break as a form of goto. https://github.com/coding-horror/basic-computer-games/blob/e...

The example at https://github.com/tokio-rs/mio/blob/master/tests/tcp.rs is a nice one

    // Wait for our TCP stream to connect

In my program, I have about 6 different components that follow the pattern below. Basically, the components run a thread while polling on crossbeam channels, file descriptors or sockets. For polling, I am using Mio (https://github.com/tokio-rs/mio).

On the code side it's pretty much the same as C++. You have a module that defines an interface and per-platform implementations that are included depending on a "configuration conditional checks" #[cfg(target_os = "linux")] macro.

https://github.com/tokio-rs/mio/blob/c6b5f13adf67483d927b176...

Made possible by Wasi support for Mio https://github.com/tokio-rs/mio/pull/1576

Indeed! In practice it's done through the polling operation: instead of a separate poll for op1 and op2, the program essentially tells the OS "wake me when either op1 or op2 is ready" (through the epoll syscall on Linux). The mio crate implements this, and the example on the readme is basically the same loop, but written with this polling strategy in mind.