[tveita]

I hope async programming doesn't become the standard in Rust. So much work has gone into allowing clean and safe threading, but people seem to be led towards the async libraries, which IMO solves a scaling problem only 1% of users will have. It's great that they exist, but if you're not expecting to have a c10k class problem, you can use threads and you'll probably have a better time.

[geofft]

If you're a library, creating threads causes side effects for the host program, and doing async when called doesn't. For instance, in a single-threaded program, it's always safe to call malloc() after fork(). In a multi-threaded program, another thread might have called malloc() and picked up a global lock; since only the thread that called fork gets copied (since you don't want to do the other threads' work twice!), there's now a copy of that global lock being held by a thread that doesn't exist, so calling malloc() will deadlock.

My personal interest in Rust is as a C replacement, including as a replacement for existing libraries that are written in C. While I agree threads can be very efficient (after all, the kernel implements threading by being async itself, more or less), they're annoying for this use case.

[staticassertion]

I just want to be able to say "do this thing or time out in 5 seconds", and that's like all the 'async' I need in rust. Everything else, nah.

But that's just me - many people need these 0 cost abstractions, this is Rust's focus, and I'll have to wait for the higher level stuff for my projects.