Crate io_tether

io-tether

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

Crates.io | API Docs

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

To get started, add io-tether to your list of dependencies

io-tether = { version = "0.1.3" }

Then in most cases, it is expected that the consumer of this library will want to implement TetherResolver on their own 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);

    let listener = tokio::net::TcpListener::bind("localhost:8080").await?;
    tokio::spawn(async move {
        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?;
    
    assert_eq!(&buf, b"foo-bar");

    Ok(())
}

Stability

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

Structs

Context

Contains metrics about the underlying connection

Tether

A wrapper type which contains the underlying I/O object, it’s initializer, and resolver.

Enums

State

The underlying cause of the I/O disconnect

Traits

TetherIo

Represents an I/O source capable of reconnecting

TetherResolver

Represents a type which drives reconnects