async.md

Async

• I/O Multiplexing

  • When waiting for data on a socket, can check non-blocking with a timeout, but has serious overhead.
  • Suppose waiting on 500 sockets and data available on one just after timeout needs to traverse 499 more to read that.
  • Maintaining thread per socket, does not scale
    • Select: Takes 3 sets of file descriptors we want to monitor for file descriptors
      • Read event
      • Write event
      • Exception event
    • Poll
      • Instead of all file descriptors only the relevant event-related are traversed
    • Epoll
      • Mush less user space to kernel space data movement

• The What and How of Futures and async/await in Rust

• Crust of Rust: async/await

  • async fn f() {} => fn f() -> impl Future<Output = ()> { async {} }
  • select mutable futures then the future itself
  • io bound faster
  • select a future

• Crust of Rust: Channels