chore(example): Autoreloading server example

[thisKai]

Motivation

I was trying to figure out whether the trick actix-web uses for autoreloading the server would work with tonic. All that was needed was to add listenfd as a dependency, install systemfd, change the following code:

Server::builder()
        .add_service(GreeterServer::new(greeter))
        .serve(addr)
        .await?;

to:

let server = Server::builder()
    .add_service(GreeterServer::new(greeter));

match listenfd::ListenFd::from_env().take_tcp_listener(0)? {
    Some(listener) => {
        let mut listener = tokio::net::TcpListener::from_std(listener)?;

        server.serve_with_incoming(listener.incoming()).await?;
    }
    None => {
        server.serve(addr).await?;
    }
}

and run:

systemfd --no-pid -s http::$ADDRESS_OR_PORT -- cargo watch -x run

Solution

I created an example with a copy of the helloworld server with these modifications, added listenfd as a dependency of the examples repository and added notes to the examples readme

[LucioFranco]

This seems like a good addition! I have a PR to fix the deny #319 then we can merge this once you mark this as ready for review!

[thisKai]

Thanks! I was hoping this would be useful to someone, I'm happy to mark it as ready since there's only one red cross left to get rid of

[LucioFranco]

@thisKai so just one question, does this work on windows? I am not super familiar with listenfd.

Looks like the CI check will pass if you rebase against master I believe.

[thisKai]

I think so, I'll check now

[thisKai]

It works, I'll rebase it now

[LucioFranco]

Thanks!