Connectors used by the Client.

This module contains:

• A default HttpConnector that does DNS resolution and establishes connections over TCP.
• Types to build custom connectors.

Connectors

A "connector" is a Service that takes a Uri destination, and its Response is some type implementing Read, Write, and Connection.

Custom Connectors

A simple connector that ignores the Uri destination and always returns a TCP connection to the same address could be written like this:

let connector = tower::service_fn(|_dst| async {
    tokio::net::TcpStream::connect("127.0.0.1:1337")
})

Or, fully written out:

use std::{future::Future, net::SocketAddr, pin::Pin, task::{self, Poll}};
use http::Uri;
use tokio::net::TcpStream;
use tower_service::Service;

#[derive(Clone)]
struct LocalConnector;

impl Service<Uri> for LocalConnector {
    type Response = TcpStream;
    type Error = std::io::Error;
    // We can't "name" an `async` generated future.
    type Future = Pin<Box<
        dyn Future<Output = Result<Self::Response, Self::Error>> + Send
    >>;

    fn poll_ready(&mut self, _: &mut task::Context<'_>) -> Poll<Result<(), Self::Error>> {
        // This connector is always ready, but others might not be.
        Poll::Ready(Ok(()))
    }

    fn call(&mut self, _: Uri) -> Self::Future {
        Box::pin(TcpStream::connect(SocketAddr::from(([127, 0, 0, 1], 1337))))
    }
}

It's worth noting that for TcpStreams, the HttpConnector is a better starting place to extend from.