The What and How of Futures and async/await in Rust
Channel: Jon Gjengset
Date: 2018-11-17

Futures are Rust's way of expressing asynchronous computations, but even after reading the documentation, it can be hard to figure out how all the pieces of futures (and tokio) fit together. While this may not matter too much if you're just *using* futures, it becomes a stumbling block once you want to implement asynchronous primitives yourself. The highly anticipated async and await keywords that are coming down the pike promise to greatly reduce the friction of writing and using asynchronous code, but add even more to the mystery of how this stuff all works.

NOTE: The YouTube transcoding process seems to have introduce audio lag on all the non-1080p versions. I'll report it to YT, but if it's bothering you, the 1080p version works fine :)

In this stream, we tackle all of this head on. We go through what futures are, how they work, how they are used to represent things like asynchronous I/O (like networking), how they are executed, and how they are evolving as they are being adopted into the standard library. We also discuss async/await, and how they affect futures, and how Rust's proposed pinning types act as the glue to make async/await work.

This is pretty dense material, but hopefully serves as a good and thorough overview of futures in Rust. If you want to know how it all works, this stream probably has you covered! To help you navigate, here are the major transition points: 



0:00:00 - Introduction

0:05:57 - What are futures?
0:16:39 - How are futures executed?
0:26:10 - Super weird audio problems
0:29:09 - All good again! (you didn't miss anything)
0:50:04 - How do you integrate futures with I/O?
1:36:11 - Driving futures with Tokio
1:49:28 - Multi-threaded future execution
2:15:00 - Stream and Sink
2:17:11 - (brief aside about tokio-io-pool)
2:24:07 - Putting futures in the standard library
2:30:00 - Arbitrary self types
2:33:46 - What is async/await?
2:46:58 - Why is async/await hard?
2:53:34 - Self-referential data-types
2:58:48 - Pinning!
3:50:40 - Q&A

The tokio documentation push is being organized at https://github.com/tokio-rs/doc-push.

You can vote for the next stream topic at https://jon.thesquareplanet.com/live-coding/ !

Live version with chat history here: https://youtu.be/fYE4qm6rbLE