Implement tower::Service for cyper::Client

[alekseysidorov]

Hi All!

I think, that it would be very useful to implement tower::Service trait for cyper::Client:

impl tower::Service<http::Request<cyper::Body>> for cyper::Client {
    type Response = http::Response<cyper::Body>;
    /// ...
}

That would allow using cyper with the whole Tower middleware ecosystem (tower::ServiceBuilder, tower-http layers: retries, timeouts, rate limits, tracing, auth, etc.).

Also, I maintain a crate tower-http-client that turns any tower::Service<http::Request<B>> into a backend-agnostic HTTP client.

Here is the main part of example:

#[derive(Debug, Deserialize)]
struct IpInfo {
    ip: String,
    country: String,
}

#[tokio::main]
async fn main() -> Result<(), BoxError> {
    eprintln!("-> Creating an HTTP client with Tower layers...");
    // First of all, we create an opaque client using the reqwest client.
    let opaque_client = into_tower_http_client(reqwest::Client::new());
    // Secondary we add some middleware to the client and then box it.
    let mut client: HttpClient = ServiceBuilder::new()
        .layer_fn(BoxCloneSyncService::new)
        .map_request(|mut request: http::Request<_>| {
            request
                .headers_mut()
                .typed_insert(UserAgent::from_static("tower-http-client"));
            request
        })
        .service(opaque_client);

    // Finally, we can use the boxed client to send requests.
    eprintln!("-> Getting IP information...");
    let response = client.get("http://api.myip.com").send().await?;
    let info = response.body_reader().json::<IpInfo>().await?;

    eprintln!("-> Got information:");
    eprintln!("   IP address: {}", info.ip);
    eprintln!("   Country: {}", info.country);

    Ok(())
}

So exposing Service would make cyper instantly compatible with that model. Happy to help with a PR if this direction looks reasonable.

[Berrysoft]

That's a good idea! Besides for http::Request, I would also like one for cyper::Request, if possible. Go ahead please! I would like to receive such a PR.