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Ergonomic and modular web framework built with Tokio, Tower, and Hyper https://crates.io/crates/axum

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David Pedersen 6f5b2708d5 A few more changes		2021-05-31 16:32:56 +02:00
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.gitignore	Initial pile of hacks	2021-05-29 21:13:06 +02:00
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README.md	A few more changes	2021-05-31 16:32:56 +02:00

README.md

tower-web

This is not https://github.com/carllerche/tower-web even though the name is the same. Its just a prototype of a minimal HTTP framework I've been toying with.

What is this?

Goals

As easy to use as tide. I don't really consider warp easy to use due to type tricks it uses. fn route() -> impl Filter<...> also isn't very ergonomic. Just async fn(Request) -> Result<Response, Error> would be nicer.
Deep integration with Tower meaning you can
- Apply middleware to the entire application.
- Apply middleware to a single route.
- Apply middleware to subset of routes.
Just focus on routing and generating responses. Tower can do the rest. Want timeouts? Use tower::timeout::Timeout. Want logging? Use tower_http::trace::Trace.
Work with Tokio. tide is cool but requires async-std.
Not macro based. Heavy macro based APIs can be very ergonomic but comes at a complexity cost. Would like to see if I can design an API that is ergonomic and doesn't require macros.

Non-goals

Runtime independent. If becoming runtime independent isn't too much then fine but explicitly designing for runtime independence isn't a goal.
Speed. As long as things are reasonably fast that is fine. For example using async-trait for ergonomics is fine even though it comes at a cost.

Example usage

Defining a single route looks like this:

let app = tower_web::app().at("/").get(root);

async fn root(req: Request<Body>) -> Result<&'static str, Error> {
    Ok("Hello, World!")
}

Adding more routes follows the same pattern:

let app = tower_web::app()
    .at("/")
    .get(root)
    .at("/users")
    .get(users_index)
    .post(users_create);

Handler functions are just async functions like:

async fn handler(req: Request<Body>) -> Result<&'static str, Error> {
    Ok("Hello, World!")
}

They most take the request as the first argument but all arguments following are called "extractors" and are used to extract data from the request (similar to rocket but no macros):

#[derive(Deserialize)]
struct UserPayload {
    username: String,
}

#[derive(Deserialize)]
struct Pagination {
    page: usize,
    per_page: usize,
}

async fn handler(
    req: Request<Body>,
    // deserialize response body with `serde_json` into a `UserPayload`
    user: extract::Json<UserPayload>,
    // deserialize query string into a `Pagination`
    pagination: extract::Query<Pagination>,
) -> Result<&'static str, Error> {
    let user: UserPayload = user.into_inner();
    let pagination: Pagination = pagination.into_inner();

    // ...
}

The inputs can also be optional:

async fn handler(
    req: Request<Body>,
    user: Option<extract::Json<UserPayload>>,
) -> Result<&'static str, Error> {
    // ...
}

You can also get the raw response body:

async fn handler(
    req: Request<Body>,
    // buffer the whole request body
    body: Bytes,
) -> Result<&'static str, Error> {
    // ...
}

Or limit the body size:

async fn handler(
    req: Request<Body>,
    // max body size in bytes
    body: extract::BytesMaxLength<1024>,
) -> Result<&'static str, Error> {
    Ok("Hello, World!")
}

Anything that implements FromRequest can work as an extractor where FromRequest is a simple async trait:

#[async_trait]
pub trait FromRequest: Sized {
    async fn from_request(req: &mut Request<Body>) -> Result<Self, Error>;
}

This "extractor" pattern is inspired by Bevy's ECS. The idea is that it should be easy to parse pick apart the request without having to repeat yourself a lot or use macros.

Dynamic routes like GET /users/:id is also supported.

You can also return different response types:

async fn string_response(req: Request<Body>) -> Result<String, Error> {
    // ...
}

// gets `content-type: appliation/json`. `Json` can contain any `T: Serialize`
async fn json_response(req: Request<Body>) -> Result<response::Json<User>, Error> {
    // ...
}

// gets `content-type: text/html`. `Html` can contain any `T: Into<Bytes>`
async fn html_response(req: Request<Body>) -> Result<response::Html<String>, Error> {
    // ...
}

// or for full control
async fn response(req: Request<Body>) -> Result<Response<Body>, Error> {
    // ...
}

You can also apply Tower middleware to single routes:

let app = tower_web::app()
    .at("/")
    .get(send_some_large_file.layer(tower_http::compression::CompressionLayer::new()))

Or to the whole app:

let service = tower_web::app()
    .at("/")
    .get(root)
    .into_service()

let app = ServiceBuilder::new()
    .timeout(Duration::from_secs(30))
    .layer(TraceLayer::new_for_http())
    .layer(CompressionLayer::new())
    .service(app);

And of course run it with Hyper:

#[tokio::main]
async fn main() {
    tracing_subscriber::fmt::init();

    // build our application with some routes
    let app = tower_web::app()
        .at("/")
        .get(handler)
        // convert it into a `Service`
        .into_service();

    // add some middleware
    let app = ServiceBuilder::new()
        .layer(TraceLayer::new_for_http())
        .service(app);

    // run it
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    tracing::debug!("listening on {}", addr);
    let server = Server::bind(&addr).serve(Shared::new(app));
    server.await.unwrap();
}

See the examples directory for more examples.

TODO

Error handling should probably be redone. Not quite sure if its bad the Error is just an enum where everything is public.
Audit which error codes we return for each kind of error. This will probably be changed when error handling is re-done.
Probably don't want to require hyper::Body for request bodies. Should have our own so hyper isn't required.
RouteBuilder should have an async fn serve(self) -> Result<(), hyper::Error> for users who just wanna create a hyper server and not care about the lower level details. Should be gated by a hyper feature.
Each new route makes a new allocation for the response body, since Or needs to unify the response body types. Would be nice to find a way to avoid that.
It should be possible to package some routes together and apply a tower middleware to that collection and then merge those routes into the app.