once_self_cell VS tokio

This issue says "Migrate code to use self_cell instead." That page says "It has undergone community code review from experienced Rust users." Looking at the review, issues were found and fixed earlier on, but my interpretation of the end of the thread is more that folks stopped responding with concerns, so confidence is now assumed but still not proven. The same was true of most (all?) other crates trying to solve the same problem, until enough people did find the unsoundness holes unique to each crate.

I've come across the zip example bevor, and even considered adding support for mutable access to the owner here https://github.com/Voultapher/self_cell/pull/36. See the last comment why I decided not to pursue this. Looking at the specific example, really what is the purpose of storing the lazy ZipReader result? IMO that's bit of bad design on the part of the zip crate. The stdlib APIs consume reader, allowing you to abstract over creation logic. If what you need to store, needs further pre-processing, why not pull that out? Specifically here, what is the point of having a self-referential struct that contains an owner ZipArchive that you will no longer be allowed to mutate. And a lazy reader ZipReader that you can then use to really read the file? If you need to abstract over the construction logic you could return (ZipArchive, Box ZipReader>), if you want to return the content you can return (ZipArchive, Vec) allowing further use of ZipArchive.

As the author of self_cell I can attest, that writing unsafe lifetime abstractions is exceedingly tricky and you will get it wrong, repeatedly. I'm not sure these problems in owning_ref can be solved without a serious overhaul of the API. For one it tracks too little information, both ouroboros and self_cell independently reached the conclusion that you have to mark the dependent as either covariant or not_covariant over the owner lifetime, and prohibit ever leaking direct references if the dependent is not_covariant. But the fun doesn't stop there, if the owner can have a lifetime too, things get extra tricky. If you want to dive deeper take a look at this discussion https://github.com/Voultapher/self_cell/pull/29.

Grouping the source and derived AST in the same struct without leaking the lifetime is something that greatly helped keep the API sane. Shameless plug https://github.com/Voultapher/self_cell

Thanks, I'll incorporate that into https://github.com/Voultapher/once_self_cell/issues/5

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).