Return a Future from app.serve

[yoshuawuyts]

Feature Request

Detailed Description

Instead of creating a runtime inside app.serve, I propose we return a future instead that allows people to run the app on whichever runtime they choose.

Context

From the API it currently isn't clear that Tide operates asynchronously. Also things like starting a database in parallel to Tide feels a bit awkward because async control flow primitives such as try_join and select don't work.

I propose we move from this:

#![feature(async_await)]

fn main() -> Result<(), failure::Error> {
    let mut app = tide::App::new(());
    app.at("/").get(async move |_| "Hello, world!");
    app.serve("127.0.0.1:8000")?;
}

To this:

#![feature(async_await)]

fn main() -> Result<(), failure::Error> {
    my_runtime::run(async {
        let mut app = tide::App::new(());
        app.at("/").get(async move |_| "Hello, world!");
        await!(app.serve("127.0.0.1:8000")?);
    })
}

We then shift the problem to making my_runtime::run nicer to use, but that's something that's worth solving for the whole async ecosystem, and not just Tide.

Possible Implementation

We would need to patch this line: https://github.com/rustasync/http-service/blob/master/http-service-hyper/src/lib.rs#L94, and propagate it through to Tide.

[secretfader]

Within the bounds of this proposal, is it possible to still provide a "batteries-included" runtime experience for new users?

[LucioFranco]

@secretfader you could have it return a custom future, that then as a function on it call say sync that will block and start the server. Under the hood it would consume itself, pass itself to a runtime.

[Texlo-Dev]

I agree with this proposal. Currently, it is a challenge to set up an asynchronous database pool with Tide, as you can't use the same runtime as Tide.

[yoshuawuyts]

With Runtime we'll be able to also get rid of most of the boilerplate this change would introduce 😊 :

#![feature(async_await)]

#[runtime::main(runtime_tokio::Tokio)]
async fn main() -> Result<(), failure::Error> {
    let mut app = tide::App::new(());
    app.at("/").get(async move |_| "Hello, world!");
    await!(app.serve("127.0.0.1:8000"))?;
}

[tirr-c]

I'm working on this, the update on http-service-hyper is here: http-rs/http-service#21

[fairingrey]

Closed via #203