I recently started working with Rust async. The main issue I am currently facing is code duplication: I have to duplicate every function that I want to support both asynchronous and blocking APIs. This could be great to have a `maybe-async`. I took a look at the available crates to work around this (maybe-async, bisync), but they all have issues or hard limitations.

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K0nserv 3 hours ago | parent | next [-]

There is work happening on keyword generics[0], which would let a function be generic over keywords like `async` and `const`.

For now the best option to write code that wants to live in both worlds is sans-io. Thomas Eizinger at Fireguard has written a good article about this[1] pattern. Not only does it nicely solve the sync/async issue, but it also makes testing easier and opens the door to techniques like DST[2]

I have my own writing on the topic[3], which highlights that the problem is wider than just async vs sync due to different executors.

0: https://github.com/rust-lang/effects-initiative

1: https://www.firezone.dev/blog/sans-io

2: https://notes.eatonphil.com/2024-08-20-deterministic-simulat...

3: https://hugotunius.se/2024/03/08/on-async-rust.html

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treyd 27 minutes ago | parent | next [-]

Keyword generics are probably not happening because it's kinda a hack.

Algebraic effects are the way forward, but that's a long way off.

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ignoreusernames 2 hours ago | parent | prev | next [-]

I may have missed something, but how does “sans-io” deal with CPU heavy code? For example, if there’s some heavy decoding/encoding required on the data? Does the event loop only drive the network side and the heavy part is done after the loop is finished?

	▲	K0nserv an hour ago \| parent [-]
		This is a great question and there isn't a definitive answer provided in the sources I linked. Broadly I think there are three approaches: 1. For frequent and small CPU heavy tasks, just run them on the IO threads. As long as you don't leave too long between `.await` points (~10ms) it seems to work okay. 2. Run your sans-io code on a dedicated CPU thread and do IO from an async runtime. This introduces overhead that needs to be weighed against the amount of CPU work. 3. Have the sans-io code output something like `Output::DoHeavyCompute { .. }` and later feed the result back as `Input::HeavyComputeResult { .. }`, in the middle run the work on a thread pool.

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paavohtl 2 hours ago | parent | prev [-]

Considering the latest commits and issues in effects-initiative are about 2 years old, the keyword generics initiative seems effectively dead.

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albertzeyer 5 hours ago | parent | prev | next [-]

The classic function coloring problem. https://journal.stuffwithstuff.com/2015/02/01/what-color-is-...

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small_scombrus 4 hours ago | parent | prev [-]

It'll depend immensely on what you're actually doing, but if it's simple enough you may be able to make a macro that subs out the types & awaits