Crate tokio_uring

Tokio-uring provides a safe io-uring interface for the Tokio runtime. The library requires Linux kernel 5.10 or later.

Getting started

Using tokio-uring requires starting a [tokio-uring] runtime. This runtime internally manages the main Tokio runtime and a io-uring driver.

use tokio_uring::fs::File;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    tokio_uring::start(async {
        // Open a file
        let file = File::open("hello.txt").await?;

        let buf = vec![0; 4096];
        // Read some data, the buffer is passed by ownership and
        // submitted to the kernel. When the operation completes,
        // we get the buffer back.
        let (res, buf) = file.read_at(buf, 0).await;
        let n = res?;

        // Display the contents
        println!("{:?}", &buf[..n]);

        Ok(())
    })
}

Under the hood, tokio_uring::start starts a [current-thread] Runtime. For concurrency, spawn multiple threads, each with a tokio-uring runtime. The tokio-uring resource types are optimized for single-threaded usage and most are !Sync.

Submit-based operations

Unlike Tokio proper, io-uring is based on submission based operations. Ownership of resources are passed to the kernel, which then performs the operation. When the operation completes, ownership is passed back to the caller. Because of this difference, the tokio-uring APIs diverge.

For example, in the above example, reading from a File requires passing ownership of the buffer.

Closing resources

With io-uring, closing a resource (e.g. a file) is an asynchronous operation. Because Rust does not support asynchronous drop yet, resource types provide an explicit close() function. If the close() function is not called, the resource will still be closed on drop, but the operation will happen in the background. There is no guarantee as to when the implicit close-on-drop operation happens, so it is recommended to explicitly call close().

Modules

• buf
  Utilities for working with buffers.
• fs
  Filesystem manipulation operations.
• net
  TCP/UDP bindings for tokio-uring.

Structs

• Builder
  Builder API to allow starting the runtime and creating the io_uring driver with non-default parameters.
• Runtime
  The Runtime executor

Functions

• builder
  Return a Builder to allow setting parameters before calling the start method. Returns a Builder with our default values, all of which can be replaced with the methods below.
• no_op
  The simplest possible operation. Just posts a completion event, nothing else.
• spawn
  Spawns a new asynchronous task, returning a JoinHandle for it.
• start
  Start an io_uring enabled Tokio runtime.
• uring_builder
  Create and return an io_uring::Builder that can then be modified through its implementation methods.

Type Definitions

• BufResult
  A specialized Result type for io-uring operations with buffers.