We have an in-house futures-based framework (inspired by Finagle) built on mio (non-blocking libevent like thing for rust). All I/O is async, but application work is often done on thread pools. Those threads are freed as soon as possible, though, so that I/O streams can be handled purely by "the reactor", and we keep the pools as small as possible.
From a parallel conversation[0] on the Rust subreddit:
>Are you going to open source anything?
>Probably. We have an in-house futures-based I/O framework. We're going to collaborate with the rust team and Carl Lerche to see if there's something there we can clean up and contribute.
