Tokio vs Async-Std

Asynchronous programming has become a crucial aspect of modern software development, allowing for more efficient use of resources and improved responsiveness. In the Rust ecosystem, two prominent libraries have emerged to facilitate asynchronous programming: tokio and async-std. Both libraries provide a way to write asynchronous code using the async/await syntax, but they differ in their approach, design, and use cases.

Tokio

tokio is a more mature library compared to async_std. This is because tokio had a pioneering role in async Rust. It provides a wide range of functionality for building asynchronous applications, including support for TCP and UDP sockets, file I/O, and HTTP clients and servers. It also has a strong focus on performance and provides many features to help developers optimize their code.

use tokio::net::TcpListener;
use tokio::prelude::*;

async fn my_tokio_function() {
    let listener = TcpListener::bind("127.0.0.1:8080").await?;
    println!("Server listening on 127.0.0.1:8080");
    loop {
        match listener.accept().await {
            Ok((stream, _)) => {
                println!("New connection");
                // Handle the connection
            }
            Err(e) => {
                println!("Error accepting connection: {}", e);
            }
        }
    }
}
#[tokio::main]
async fn main() {
    my_tokio_function().await;
}

Async-Std

async-std is the library provided by the standard library designed specifically for building asynchronous applications. It provides a set of basic types and functions that can be used to create asynchronous code. Its promise is that you could almost use it as a drop-in replacement. For instance, an operation for read a file in non-async Rust:

use std::fs::File;
use std::io::Read;

fn main() -> std::io::Result<()> {
    let mut file = File::open("foo.txt")?;
    let mut data = vec![];
    file.read_to_end(&mut data)?;
    Ok(())
}

In async_std the same operation is transformed as:

use async_std::prelude::*;
use async_std::fs::File;
use async_std::io;

async fn read_file(path: &str) -> io::Result<()> {
    let mut file = File::open(path).await?;
    let mut data = vec![];
    file.read_to_end(&mut data).await?;
    Ok(())
}

Which one to use?

Both tokio and async_std are powerful libraries for building asynchronous applications in Rust. While async_std is a good choice for simple use cases and integrating with the standard library, tokio provides more advanced features and better performance.

When choosing between the two libraries, consider the complexity of your project and the level of control you need over the underlying network and file I/O operations. If you’re building a simple web server or a small-scale asynchronous application, async_std might be a good choice. However, if you’re building a more complex system that requires advanced features and performance optimization, tokio is likely a better fit.

Ultimately, the choice between tokio and async_std depends on your specific needs and preferences as a developer. Both libraries are well-maintained and provide a great way to write asynchronous code in Rust.