nix VS tokio

If we drop std Rust ceases to be economical due to the time it would take to reimplement the data structures and IO interfaces it provides, not to mention the event loop crate we use (calloop). At that point we'd be relying on so much FFI via eg. nix that the relative safety would be diminished too. After reimplementing all that it's not clear to me that we'd even save that much size, but I suppose it's possible.

Now that we have covered the fundamentals of signals, let's delve into the world of handling signals in Rust! Unlike C, where signal handling is built into the language modules, Rust provides several libraries that enable developers to handle signals with ease. Libraries such as signal_hook, nix, libc, and tokio handle signals that primarily use C bindings to make it possible to work with signals.

Obviously you meant the nix crate

Finally, there's the nix crate, which provides a safe Rust API over the libc functions.

You can take a look here for example: https://github.com/nix-rust/nix/blob/master/CHANGELOG.md

Unsafe code can in principle speed up I/O by calling libc for special syscalls, but uutils typically uses safe wrappers from nix instead. Very rarely there's a line of unsafe code needed to sand off the edges.

This post fails to speak to me on two fronts:

* The `nix` crate is a cornerstone of the Rust development ecosystem: if you do anything that requires POSIX or various nix-specific APIs beyond those wrapped by the standard library, then `nix` most likely provides a high-level and safe* wrapper for them. Perfectionism is a virtue in this context, one that keeps large parts of the Rust ecosystem from accidentally consuming buggy code. The author unfortunately chose a particularly messy and bug-prone corner of the POSIX APIs to wrap, and ran into a correspondingly intensive review process. I've merged simpler wrappers[1][2] with no fuss.

* Alacritty seems to work just fine. I switched to it about two months ago, after using nothing but (heavily customized) rxvt-unicode for a decade. Maybe it's because I don't use ligatures or images in my terminals (I thought we were talking about non-"toy" functionality!), but I haven't found myself wanting for anything beyond what Alacritty already does. And the scrollback seems to work nicely. To summarize: where's the tragedy?

[1]: https://github.com/nix-rust/nix/pull/1342

[2]: https://github.com/nix-rust/nix/pull/1331

One thing I'd like to see is a MSRV policy, as its causing problems for downstreams (https://github.com/nix-rust/nix/issues/1555)

Being able to control nondeterminism is particularly useful for testing and debugging. This allows creating reproducible test environments, as well as discrete-event simulation for faster-than-real-time simulation of time delays. For example, Cardano uses a simulation environment for the IO monad that closely follows core Haskell packages; Sui has a simulator based on madsim that provides an API-compatible replacement for the Tokio runtime and intercepts various POSIX API calls in order to enforce determinism. Both allow running the same code in production as in the simulator for testing.

tokio / hyper / toml / serde / serde_json / json5 / console

tokio - An asynchronous runtime for Rust

3. Tokio

The AWS SDK makes use of the async capabilities in the Tokio library. So when you see async in front of a fn that function is capable of executing asynchronously.

Petar is also looking at implementing concurrency the way it is in Go to have a fully functional virtual machine as it is in the spec. This would likely attract more external contributors to developing the VM. One advantage of Rust is that, with the concurrency model, there is already an extensive library called Tokio which he can use. Petar stresses that this isn’t easy, but he believes it’s achievable, at least as a research topic around determinism and concurrency.

Another thing to point out is that async is a thing in Rust. I'm not going to begin to dive into this paradigm in this article, but know it's handled by the awesome Tokio framework.

So I started by using Tokio, a popular async runtime. The docs and samples helped me get a simple outbound TCP connection working. The Rust async book also had a lot of good explanations, both practical and digging into the details of what a runtime does.

Regarding the quote:

> The Original Sin of Rust async programming is making it multi-threaded by default. If premature optimization is the root of all evil, this is the mother of all premature optimizations, and it curses all your code with the unholy Send + 'static, or worse yet Send + Sync + 'static, which just kills all the joy of actually writing Rust.

Agree about the melodramatic tone. I also don't think removing the Send + Sync really makes that big a difference. It's the 'static that bothers me the most. I want scoped concurrency. Something like <https://github.com/tokio-rs/tokio/issues/2596>.

Another thing I really hate about Rust async right now is the poor instrumentation. I'm having a production problem at work right now in which some tasks just get stuck. I wish I could do the equivalent of `gdb; thread apply all bt`. Looking forward to <https://github.com/tokio-rs/tokio/issues/5638> landing at least. It exists right now but is experimental and in my experience sometimes panics. I'm actually writing a PR today to at least use the experimental version on SIGTERM to see what's going on, on the theory that if it crashes oh well, we're shutting down anyway.

Neither of these complaints would be addressed by taking away work stealing. In fact, I could keep doing down my list, and taking away work stealing wouldn't really help with much of anything.

The PHP <-> Rust bindings are provided by https://github.com/Nicelocal/ext-php-rs/ (our fork of https://github.com/davidcole1340/ext-php-rs with a bunch of UX improvements :).

php-tokio's integrates the https://revolt.run event loop with the https://tokio.rs event loop; async functionality is provided by the two event loops, in combination with PHP fibers through revolt's suspension API (I could've directly used the PHP Fiber API to provide coroutine suspension, but it was a tad easier with revolt's suspension API (https://revolt.run/fibers), since it also handles the base case of suspension in the main fiber).