Crate tower_http

Expand description

async fn(HttpRequest) -> Result<HttpResponse, Error>

Overview

tower-http is a library that provides HTTP-specific middleware and utilities built on top of tower.

All middleware uses the http and http-body crates as the HTTP abstractions. That means they’re compatible with any library or framework that also uses those crates, such as hyper, tonic, and warp.

Example server

This example shows how to apply middleware from tower-http to a Service and then run that service using hyper.

use tower_http::{
    add_extension::AddExtensionLayer,
    compression::CompressionLayer,
    propagate_header::PropagateHeaderLayer,
    auth::RequireAuthorizationLayer,
    sensitive_headers::SetSensitiveRequestHeadersLayer,
    set_header::SetResponseHeaderLayer,
    trace::TraceLayer,
    validate_request::ValidateRequestHeaderLayer,
};
use tower::{ServiceBuilder, service_fn, make::Shared};
use http::{Request, Response, header::{HeaderName, CONTENT_TYPE, AUTHORIZATION}};
use hyper::{Body, Error, server::Server, service::make_service_fn};
use std::{sync::Arc, net::SocketAddr, convert::Infallible, iter::once};

// Our request handler. This is where we would implement the application logic
// for responding to HTTP requests...
async fn handler(request: Request<Body>) -> Result<Response<Body>, Error> {
    // ...
}

// Shared state across all request handlers --- in this case, a pool of database connections.
struct State {
    pool: DatabaseConnectionPool,
}

#[tokio::main]
async fn main() {
    // Construct the shared state.
    let state = State {
        pool: DatabaseConnectionPool::new(),
    };

    // Use tower's `ServiceBuilder` API to build a stack of tower middleware
    // wrapping our request handler.
    let service = ServiceBuilder::new()
        // Mark the `Authorization` request header as sensitive so it doesn't show in logs
        .layer(SetSensitiveRequestHeadersLayer::new(once(AUTHORIZATION)))
        // High level logging of requests and responses
        .layer(TraceLayer::new_for_http())
        // Share an `Arc<State>` with all requests
        .layer(AddExtensionLayer::new(Arc::new(state)))
        // Compress responses
        .layer(CompressionLayer::new())
        // Propagate `X-Request-Id`s from requests to responses
        .layer(PropagateHeaderLayer::new(HeaderName::from_static("x-request-id")))
        // If the response has a known size set the `Content-Length` header
        .layer(SetResponseHeaderLayer::overriding(CONTENT_TYPE, content_length_from_response))
        // Authorize requests using a token
        .layer(RequireAuthorizationLayer::bearer("passwordlol"))
        // Accept only application/json, application/* and */* in a request's ACCEPT header
        .layer(ValidateRequestHeaderLayer::accept("application/json"))
        // Wrap a `Service` in our middleware stack
        .service_fn(handler);

    // And run our service using `hyper`
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    Server::bind(&addr)
        .serve(Shared::new(service))
        .await
        .expect("server error");
}

Keep in mind that while this example uses hyper, tower-http supports any HTTP client/server implementation that uses the http and http-body crates.

Example client

tower-http middleware can also be applied to HTTP clients:

use tower_http::{
    decompression::DecompressionLayer,
    set_header::SetRequestHeaderLayer,
    trace::TraceLayer,
    classify::StatusInRangeAsFailures,
};
use tower::{ServiceBuilder, Service, ServiceExt};
use hyper::Body;
use http::{Request, HeaderValue, header::USER_AGENT};

#[tokio::main]
async fn main() {
    let mut client = ServiceBuilder::new()
        // Add tracing and consider server errors and client
        // errors as failures.
        .layer(TraceLayer::new(
            StatusInRangeAsFailures::new(400..=599).into_make_classifier()
        ))
        // Set a `User-Agent` header on all requests.
        .layer(SetRequestHeaderLayer::overriding(
            USER_AGENT,
            HeaderValue::from_static("tower-http demo")
        ))
        // Decompress response bodies
        .layer(DecompressionLayer::new())
        // Wrap a `hyper::Client` in our middleware stack.
        // This is possible because `hyper::Client` implements
        // `tower::Service`.
        .service(hyper::Client::new());

    // Make a request
    let request = Request::builder()
        .uri("http://example.com")
        .body(Body::empty())
        .unwrap();

    let response = client
        .ready()
        .await
        .unwrap()
        .call(request)
        .await
        .unwrap();
}

Feature Flags

All middleware are disabled by default and can be enabled using cargo features.

For example, to enable the Trace middleware, add the “trace” feature flag in your Cargo.toml:

tower-http = { version = "0.1", features = ["trace"] }

You can use "full" to enable everything:

tower-http = { version = "0.1", features = ["full"] }

If you’re new to tower its guides might help. In the tower-http repo we also have a number of examples showing how to put everything together. You’re also welcome to ask in the #tower Discord channel or open an issue with your question.