Leaf futures

Runtimes create leaf futures, which represent a resource such as a socket.

This is an example of a leaf future:

let mut stream = tokio::net::TcpStream::connect("127.0.0.1:3000");

Operations on these resources, such as a reading from a socket, will be non-blocking and return a future, which we call a leaf future since it’s the future that we’re actually waiting on.

It’s unlikely that you’ll implement a leaf future yourself unless you’re writing a runtime, but we’ll go through how they’re constructed in this book as well.

It’s also unlikely that you’ll pass a leaf future to a runtime and run it to completion alone, as you’ll understand by reading the next paragraph.