| examples | ||
| src | ||
| .gitignore | ||
| Cargo.toml | ||
| README.md | ||
tower-web
tower-web (name pending) is a tiny web application framework that focuses on ergonomics and modularity.
Goals
- Ease of use. Building web apps in Rust should be as easy as
async fn handle(Request) -> Response. - Solid foundation. tower-web is built on top of tower and makes it easy to plug in any middleware from the tower and tower-http ecosystem.
- Focus on routing, extracting data from requests, and generating responses. Tower middleware can handle the rest.
- Macro free core. Macro frameworks have their place but tower-web focuses on providing a core that is macro free.
Compatibility
tower-web is designed to work with tokio and hyper. Runtime and transport layer independence is not a goal, at least for the time being.
Example
The "Hello, World!" of tower-web is:
use tower_web::prelude::*;
use hyper::Server;
use std::net::SocketAddr;
use tower::make::Shared;
#[tokio::main]
async fn main() {
// build our application with a single route
let app = route("/", get(|| async { "Hello, World!" }));
// run it with hyper on localhost:3000
let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
Server::bind(&addr)
.serve(Shared::new(app))
.await
.unwrap();
}
Routing
Routing between handlers looks like this:
use tower_web::prelude::*;
let app = route("/", get(get_slash).post(post_slash))
.route("/foo", get(get_foo));
async fn get_slash() {
// `GET /` called
}
async fn post_slash() {
// `POST /` called
}
async fn get_foo() {
// `GET /foo` called
}
Routes can also be dynamic like /users/:id. See "Extracting data from
requests" for more details on that.
Responses
Anything that implements IntoResponse can be
returned from a handler:
use tower_web::{body::Body, response::{Html, Json}, prelude::*};
use http::{StatusCode, Response, Uri};
use serde_json::{Value, json};
// We've already seen returning &'static str
async fn plain_text() -> &'static str {
"foo"
}
// String works too and will get a text/plain content-type
async fn plain_text_string(uri: Uri) -> String {
format!("Hi from {}", uri.path())
}
// Bytes will get a `application/octet-stream` content-type
async fn bytes() -> Vec<u8> {
vec![1, 2, 3, 4]
}
// `()` gives an empty response
async fn empty() {}
// `StatusCode` gives an empty response with that status code
async fn empty_with_status() -> StatusCode {
StatusCode::NOT_FOUND
}
// A tuple of `StatusCode` and something that implements `IntoResponse` can
// be used to override the status code
async fn with_status() -> (StatusCode, &'static str) {
(StatusCode::INTERNAL_SERVER_ERROR, "Something went wrong")
}
// `Html` gives a content-type of `text/html`
async fn html() -> Html<&'static str> {
Html("<h1>Hello, World!</h1>")
}
// `Json` gives a content-type of `application/json` and works with any type
// that implements `serde::Serialize`
async fn json() -> Json<Value> {
Json(json!({ "data": 42 }))
}
// `Result<T, E>` where `T` and `E` implement `IntoResponse` is useful for
// returning errors
async fn result() -> Result<&'static str, StatusCode> {
Ok("all good")
}
// `Response` gives full control
async fn response() -> Response<Body> {
Response::builder().body(Body::empty()).unwrap()
}
let app = route("/plain_text", get(plain_text))
.route("/plain_text_string", get(plain_text_string))
.route("/bytes", get(bytes))
.route("/empty", get(empty))
.route("/empty_with_status", get(empty_with_status))
.route("/with_status", get(with_status))
.route("/html", get(html))
.route("/json", get(json))
.route("/result", get(result))
.route("/response", get(response));
See the [response] module for more details.
Extracting data from requests
A handler function is an async function take takes any number of
"extractors" as arguments. An extractor is a type that implements
FromRequest.
For example, [extract::Json] is an extractor that consumes the request
body and deserializes it as JSON into some target type:
use tower_web::prelude::*;
use serde::Deserialize;
let app = route("/users", post(create_user));
#[derive(Deserialize)]
struct CreateUser {
email: String,
password: String,
}
async fn create_user(payload: extract::Json<CreateUser>) {
let payload: CreateUser = payload.0;
// ...
}
[extract::UrlParams] can be used to extract params from a dynamic URL. It
is compatible with any type that implements [std::str::FromStr], such as
Uuid:
use tower_web::prelude::*;
use uuid::Uuid;
let app = route("/users/:id", post(create_user));
async fn create_user(params: extract::UrlParams<(Uuid,)>) {
let user_id: Uuid = (params.0).0;
// ...
}
There is also UrlParamsMap which provide a map
like API for extracting URL params.
You can also apply multiple extractors:
use tower_web::prelude::*;
use uuid::Uuid;
use serde::Deserialize;
let app = route("/users/:id/things", get(get_user_things));
#[derive(Deserialize)]
struct Pagination {
page: usize,
per_page: usize,
}
impl Default for Pagination {
fn default() -> Self {
Self { page: 1, per_page: 30 }
}
}
async fn get_user_things(
params: extract::UrlParams<(Uuid,)>,
pagination: Option<extract::Query<Pagination>>,
) {
let user_id: Uuid = (params.0).0;
let pagination: Pagination = pagination.unwrap_or_default().0;
// ...
}
Additionally Request<Body> is itself an extractor:
use tower_web::prelude::*;
let app = route("/users/:id", post(handler));
async fn handler(req: Request<Body>) {
// ...
}
However it cannot be combined with other extractors since it consumes the entire request.
See the [extract] module for more details.
Applying middleware
tower-web is designed to take full advantage of the tower and tower-http ecosystem of middleware:
Applying middleware to individual handlers
A middleware can be applied to a single handler like so:
use tower_web::prelude::*;
use tower::limit::ConcurrencyLimitLayer;
let app = route(
"/",
get(handler.layer(ConcurrencyLimitLayer::new(100))),
);
async fn handler() {}
Applying middleware to groups of routes
Middleware can also be applied to a group of routes like so:
use tower_web::prelude::*;
use tower::limit::ConcurrencyLimitLayer;
let app = route("/", get(get_slash))
.route("/foo", post(post_foo))
.layer(ConcurrencyLimitLayer::new(100));
async fn get_slash() {}
async fn post_foo() {}
Error handling
tower-web requires all errors to be handled. That is done by using
[std::convert::Infallible] as the error type in all its [Service]
implementations.
For handlers created from async functions this is works automatically since
handlers must return something that implements
IntoResponse, even if its a Result.
However middleware might add new failure cases that has to be handled. For
that tower-web provides a handle_error
combinator:
use tower_web::prelude::*;
use tower::{
BoxError, timeout::{TimeoutLayer, error::Elapsed},
};
use std::{borrow::Cow, time::Duration};
use http::StatusCode;
let app = route(
"/",
get(handle
.layer(TimeoutLayer::new(Duration::from_secs(30)))
// `Timeout` uses `BoxError` as the error type
.handle_error(|error: BoxError| {
// Check if the actual error type is `Elapsed` which
// `Timeout` returns
if error.is::<Elapsed>() {
return (StatusCode::REQUEST_TIMEOUT, "Request took too long".into());
}
// If we encounter some error we don't handle return a generic
// error
return (
StatusCode::INTERNAL_SERVER_ERROR,
// `Cow` lets us return either `&str` or `String`
Cow::from(format!("Unhandled internal error: {}", error)),
);
})),
);
async fn handle() {}
The closure passed to handle_error must
return something that implements IntoResponse.
handle_error is also available on a
group of routes with middleware applied:
use tower_web::prelude::*;
use tower::{BoxError, timeout::TimeoutLayer};
use std::time::Duration;
let app = route("/", get(handle))
.route("/foo", post(other_handle))
.layer(TimeoutLayer::new(Duration::from_secs(30)))
.handle_error(|error: BoxError| {
// ...
});
async fn handle() {}
async fn other_handle() {}
Applying multiple middleware
[tower::ServiceBuilder] can be used to combine multiple middleware:
use tower_web::prelude::*;
use tower::{
ServiceBuilder, BoxError,
load_shed::error::Overloaded,
timeout::error::Elapsed,
};
use tower_http::compression::CompressionLayer;
use std::{borrow::Cow, time::Duration};
use http::StatusCode;
let middleware_stack = ServiceBuilder::new()
// Return an error after 30 seconds
.timeout(Duration::from_secs(30))
// Shed load if we're receiving too many requests
.load_shed()
// Process at most 100 requests concurrently
.concurrency_limit(100)
// Compress response bodies
.layer(CompressionLayer::new())
.into_inner();
let app = route("/", get(|_: Request<Body>| async { /* ... */ }))
.layer(middleware_stack)
.handle_error(|error: BoxError| {
if error.is::<Overloaded>() {
return (
StatusCode::SERVICE_UNAVAILABLE,
"Try again later".into(),
);
}
if error.is::<Elapsed>() {
return (
StatusCode::REQUEST_TIMEOUT,
"Request took too long".into(),
);
};
return (
StatusCode::INTERNAL_SERVER_ERROR,
Cow::from(format!("Unhandled internal error: {}", error)),
);
});
Sharing state with handlers
It is common to share some state between handlers for example to share a
pool of database connections or clients to other services. That can be done
using the [AddExtension] middleware (applied with [AddExtensionLayer])
and the [extract::Extension] extractor:
use tower_web::{AddExtensionLayer, prelude::*};
use std::sync::Arc;
struct State {
// ...
}
let shared_state = Arc::new(State { /* ... */ });
let app = route("/", get(handler)).layer(AddExtensionLayer::new(shared_state));
async fn handler(
state: extract::Extension<Arc<State>>,
) {
let state: Arc<State> = state.0;
// ...
}
Routing to any [Service]
tower-web also supports routing to general [Service]s:
use tower_web::{
// `ServiceExt` adds `handle_error` to any `Service`
service::{self, ServiceExt}, prelude::*,
};
use tower_http::services::ServeFile;
use http::Response;
use std::convert::Infallible;
use tower::{service_fn, BoxError};
let app = route(
// Any request to `/` goes to a service
"/",
service_fn(|_: Request<Body>| async {
let res = Response::new(Body::from("Hi from `GET /`"));
Ok::<_, Infallible>(res)
})
).route(
// GET `/static/Cargo.toml` goes to a service from tower-http
"/static/Cargo.toml",
service::get(
ServeFile::new("Cargo.toml")
// Errors must be handled
.handle_error(|error: std::io::Error| { /* ... */ })
)
);
Routing to arbitrary services in this way has complications for backpressure
([Service::poll_ready]). See the [service] module for more details.
Nesting applications
Applications can be nested by calling nest:
use tower_web::{prelude::*, routing::BoxRoute, body::BoxBody};
use tower_http::services::ServeFile;
use http::Response;
use std::convert::Infallible;
fn api_routes() -> BoxRoute<BoxBody> {
route("/users", get(|_: Request<Body>| async { /* ... */ })).boxed()
}
let app = route("/", get(|_: Request<Body>| async { /* ... */ }))
.nest("/api", api_routes());
nest can also be used to serve static files from a directory:
use tower_web::{prelude::*, service::ServiceExt, routing::nest};
use tower_http::services::ServeDir;
use http::Response;
use std::convert::Infallible;
use tower::{service_fn, BoxError};
let app = nest(
"/images",
ServeDir::new("public/images").handle_error(|error: std::io::Error| {
// ...
})
);