io-tether

Traits for defining I/O objects which automatically reconnect upon failure.

This project is similar in scope to stubborn-io, but aims to leverage the recently stabilized async fn in traits, to make the implementation of reconnecting simpler for the end user.

Usage

In most cases, it is expected that the consumer of this library will want to implement their own TetherResolver types. This allows them to inject arbitrary asynchronous code just before the I/O attempts to reconnect.

use io_tether::{TetherResolver, Context, State, Tether};
use tokio::{net::TcpStream, io::{AsyncReadExt, AsyncWriteExt}, sync::mpsc};

/// Custom resolver
pub struct CallbackResolver {
    channel: mpsc::Sender<String>,
}

impl TetherResolver for CallbackResolver {
    type Error = std::io::Error;

    async fn disconnected(
        &mut self,
        context: &Context,
        state: &State<Self::Error>,
    ) -> bool {
        match state {
            State::Eof => false, // No reconnection attempt will be made
            State::Err(error) => {
                let error = error.to_string();
                self.channel.send(error).await.unwrap();
                true
            }
        }
    }
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut buf = Vec::new();
    let (channel, rx) = mpsc::channel(10);

	tokio::spawn(async move {
		let listener = tokio::net::TcpListener::bind("localhost:8080").await.unwrap();
		loop {
			let (mut stream, _addr) = listener.accept().await.unwrap();
			stream.write_all(b"foo-bar").await.unwrap();
			stream.shutdown().await.unwrap();
		}
	});

    let resolver = CallbackResolver {
        channel,
    };
    let mut tether = Tether::<_, TcpStream, _>::connect("localhost:8080", resolver)
        .await?;

    tether.read_to_end(&mut buf).await.unwrap();
	
	assert_eq!(&buf, b"foo-bar");

    Ok(())
}

State

This project is still very much a work in progress, expect fairly common breaking changes in the short term.