Building Web API's With Rust 1

When you start building stuff with Rust, you notice that applications are made of small, specialized libraries.

The product I want to build is a web application, just a regular one, will receive HTTP requests, respond accordingly and it might call other HTTP services.

To start, I’m using hyper, a very lightweight HTTP server. It leverages the library tokio and futures for async capabilities. I recommend reading tokio’s documentation to understand more how the async part works with rust.

What I currently have (sort of hello word)

My tests should perform a call to the root url ”/” and another to an unkown url. This is just to make sure it compiles and runs.

Cargo.toml

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[dependencies] hyper = “0.12” futures = “0.1” pretty_env_logger = “0.3” log = “0.4”

[dev-dependencies] speculate = “0.1” reqwest = “0.9”

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main.rs

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use hyper::service::service_fn; use hyper::{Body, Method, Request, Response, Server, StatusCode}; use futures::{future, Future};

use std::env;

extern crate pretty_env_logger; #[macro_use] extern crate log;

type InternalServerError = Box<dyn std::error::Error + Send + Sync>; type BoxedResponseFuture = Box<dyn Future<Item = Response, Error = InternalServerError> + Send>;

fn main() { env::set_var(“RUST_LOG”, “app=debug”); env::set_var(“RUST_BACKTRACE”, “1”); pretty_env_logger::init();

let addr = "0.0.0.0:3000".parse().unwrap();

let new_service = || service_fn(move |req| router(req));

let server = Server::bind(&addr)
    .serve(new_service)
    .map_err(|e| eprintln!("server error: {}", e));

info!("Listening on http://{}", addr);
hyper::rt::run(server);

}

fn router(req: Request) -> BoxedResponseFuture { info!(“INFO {:?}”, req);

match (req.method(), req.uri().path()) {
    (&Method::GET, "/") => index(),
    _ => handle_404(),
}

}

fn handle_404() -> BoxedResponseFuture { Box::new(future::ok( Response::builder() .status(StatusCode::NOT_FOUND) .body(Body::empty()) .unwrap(), )) }

fn index() -> BoxedResponseFuture { Box::new(future::ok( Response::builder() .status(StatusCode::OK) .body(Body::empty()) .unwrap(), )) }

#[cfg(test)] mod tests { extern crate speculate; extern crate reqwest as request;

use hyper::StatusCode;
use speculate::speculate;    
use std::thread;
use std::sync::Once;

use super::main;

static SETUP: Once = Once::new();    

speculate! {      
    before {
        SETUP.call_once(|| {
            let _main_server = thread::spawn(main);
        });
    }

    describe "main server routes" {
        it "calls the root path and returns 200" {
            let resp = request::get("http://0.0.0.0:3000").unwrap();
            assert!(resp.status().is_success());
        }

        it "calls an inexistent route and returns 404" {
            let resp = request::get("http://0.0.0.0:3000/notfound").unwrap();
            assert!(resp.status().is_client_error());
            assert_eq!(resp.status(), StatusCode::NOT_FOUND);
        }
    }
}

} {{< / highlight >}}

{{< highlight shell >}} running 2 tests INFO app > Listening on http://0.0.0.0:3000 INFO app > INFO Request { method: GET, uri: /, version: HTTP/1.1, headers: {“user-agent”: “reqwest/0.9.22”, “accept”: ”/”, “accept-encoding”: “gzip”, “host”: “0.0.0.0:3000”}, body: Body(Empty) } INFO app > INFO Request { method: GET, uri: /notfound, version: HTTP/1.1, headers: {“user-agent”: “reqwest/0.9.22”, “accept”: ”/”, “accept-encoding”: “gzip”, “host”: “0.0.0.0:3000”}, body: Body(Empty) } test tests::speculate_0::main_server_routes::test_calls_an_inexistent_route_and_returns_404 … ok test tests::speculate_0::main_server_routes::test_calls_the_root_path_and_returns_200 … ok

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

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The libraries pretty_env_logger and log are for logging purposes.
The library speculate helps structuring my tests.
The library reqwest provides a high level API for making HTTP requests.

Next, I need to figure out how to properly set up routes for the app.

Note on running tests: I managed to bootstrap the server only once on tests using the struct Once. Otherwise every test would try to spawn a thread with the server (they still do, but Once prevents it)