| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="`async fn(Request) -> Result<Response, Error>`"><meta name="keywords" content="rust, rustlang, rust-lang, tower"><title>tower - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../normalize.css"><link rel="stylesheet" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../ayu.css" disabled><link rel="stylesheet" href="../dark.css" disabled><link rel="stylesheet" href="../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../storage.js"></script><script defer src="../crates.js"></script><script defer src="../main.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../favicon.svg"></head><body class="rustdoc mod crate"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button><a class="sidebar-logo" href="../tower/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><h2></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../tower/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><h2 class="location"><a href="#">Crate tower</a></h2><div class="sidebar-elems"><ul class="block"><li class="version">Version 0.4.13</li><li><a id="all-types" href="all.html">All Items</a></li></ul><section><ul class="block"><li><a href="#modules">Modules</a></li><li><a href="#structs">Structs</a></li><li><a href="#traits">Traits</a></li><li><a href="#functions">Functions</a></li><li><a href="#types">Type Definitions</a></li></ul></section></div></nav><main><div class="width-limiter"><nav class="sub"><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn">Crate <a class="mod" href="#">tower</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../clipboard.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="srclink" href="../src/tower/lib.rs.html#1-242">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p><code>async fn(Request) -> Result<Response, Error></code></p> |
| <h2 id="overview"><a href="#overview">Overview</a></h2> |
| <p>Tower is a library of modular and reusable components for building |
| robust networking clients and servers.</p> |
| <p>Tower provides a simple core abstraction, the <a href="trait.Service.html"><code>Service</code></a> trait, which |
| represents an asynchronous function taking a request and returning either a |
| response or an error. This abstraction can be used to model both clients and |
| servers.</p> |
| <p>Generic components, like <a href="timeout/index.html">timeouts</a>, <a href="limit/rate/index.html">rate limiting</a>, and <a href="balance/index.html">load balancing</a>, |
| can be modeled as <a href="trait.Service.html"><code>Service</code></a>s that wrap some inner service and apply |
| additional behavior before or after the inner service is called. This allows |
| implementing these components in a protocol-agnostic, composable way. Typically, |
| such services are referred to as <em>middleware</em>.</p> |
| <p>An additional abstraction, the <a href="trait.Layer.html"><code>Layer</code></a> trait, is used to compose |
| middleware with <a href="trait.Service.html"><code>Service</code></a>s. If a <a href="trait.Service.html"><code>Service</code></a> can be thought of as an |
| asynchronous function from a request type to a response type, a <a href="trait.Layer.html"><code>Layer</code></a> is |
| a function taking a <a href="trait.Service.html"><code>Service</code></a> of one type and returning a <a href="trait.Service.html"><code>Service</code></a> of a |
| different type. The <a href="struct.ServiceBuilder.html"><code>ServiceBuilder</code></a> type is used to add middleware to a |
| service by composing it with multiple <a href="trait.Layer.html"><code>Layer</code></a>s.</p> |
| <h3 id="the-tower-ecosystem"><a href="#the-tower-ecosystem">The Tower Ecosystem</a></h3> |
| <p>Tower is made up of the following crates:</p> |
| <ul> |
| <li><a href="https://crates.io/crates/tower"><code>tower</code></a> (this crate)</li> |
| <li><a href="https://crates.io/crates/tower-service"><code>tower-service</code></a></li> |
| <li><a href="https://crates.io/crates/tower-layer"><code>tower-layer</code></a></li> |
| <li><a href="https://crates.io/crates/tower-test"><code>tower-test</code></a></li> |
| </ul> |
| <p>Since the <a href="trait.Service.html"><code>Service</code></a> and <a href="trait.Layer.html"><code>Layer</code></a> traits are important integration points |
| for all libraries using Tower, they are kept as stable as possible, and |
| breaking changes are made rarely. Therefore, they are defined in separate |
| crates, <a href="https://crates.io/crates/tower-service"><code>tower-service</code></a> and <a href="https://crates.io/crates/tower-layer"><code>tower-layer</code></a>. This crate contains |
| re-exports of those core traits, implementations of commonly-used |
| middleware, and <a href="trait.ServiceExt.html">utilities</a> for working with <a href="trait.Service.html"><code>Service</code></a>s and <a href="trait.Layer.html"><code>Layer</code></a>s. |
| Finally, the <a href="https://crates.io/crates/tower-test"><code>tower-test</code></a> crate provides tools for testing programs using |
| Tower.</p> |
| <h2 id="usage"><a href="#usage">Usage</a></h2> |
| <p>Tower provides an abstraction layer, and generic implementations of various |
| middleware. This means that the <code>tower</code> crate on its own does <em>not</em> provide |
| a working implementation of a network client or server. Instead, Tower’s |
| <a href="trait.Service.html"><code>Service</code> trait</a> provides an integration point between |
| application code, libraries providing middleware implementations, and |
| libraries that implement servers and/or clients for various network |
| protocols.</p> |
| <p>Depending on your particular use case, you might use Tower in several ways:</p> |
| <ul> |
| <li> |
| <p><strong>Implementing application logic</strong> for a networked program. You might |
| use the <a href="trait.Service.html"><code>Service</code></a> trait to model your application’s behavior, and use |
| the middleware <a href="#modules">provided by this crate</a> and by other libraries |
| to add functionality to clients and servers provided by one or more |
| protocol implementations.</p> |
| </li> |
| <li> |
| <p><strong>Implementing middleware</strong> to add custom behavior to network clients and |
| servers in a reusable manner. This might be general-purpose middleware |
| (and if it is, please consider releasing your middleware as a library for |
| other Tower users!) or application-specific behavior that needs to be |
| shared between multiple clients or servers.</p> |
| </li> |
| <li> |
| <p><strong>Implementing a network protocol</strong>. Libraries that implement network |
| protocols (such as HTTP) can depend on <code>tower-service</code> to use the |
| <a href="trait.Service.html"><code>Service</code></a> trait as an integration point between the protocol and user |
| code. For example, a client for some protocol might implement <a href="trait.Service.html"><code>Service</code></a>, |
| allowing users to add arbitrary Tower middleware to those clients. |
| Similarly, a server might be created from a user-provided <a href="trait.Service.html"><code>Service</code></a>.</p> |
| <p>Additionally, when a network protocol requires functionality already |
| provided by existing Tower middleware, a protocol implementation might use |
| Tower middleware internally, as well as as an integration point.</p> |
| </li> |
| </ul> |
| <h3 id="library-support"><a href="#library-support">Library Support</a></h3> |
| <p>A number of third-party libraries support Tower and the <a href="trait.Service.html"><code>Service</code></a> trait. |
| The following is an incomplete list of such libraries:</p> |
| <ul> |
| <li><a href="https://crates.io/crates/hyper"><code>hyper</code></a>: A fast and correct low-level HTTP implementation.</li> |
| <li><a href="https://crates.io/crates/tonic"><code>tonic</code></a>: A <a href="https://grpc.io">gRPC-over-HTTP/2</a> implementation built on top of |
| <a href="https://crates.io/crates/hyper"><code>hyper</code></a>. See <a href="https://github.com/hyperium/tonic/tree/master/examples/src/tower">here</a> for examples of using <a href="https://crates.io/crates/tonic"><code>tonic</code></a> with |
| Tower.</li> |
| <li><a href="https://crates.io/crates/warp"><code>warp</code></a>: A lightweight, composable web framework. See |
| <a href="https://docs.rs/warp/0.2.5/warp/fn.service.html">here</a> for details on using <a href="https://crates.io/crates/warp"><code>warp</code></a> with Tower.</li> |
| <li><a href="https://crates.io/crates/tower-lsp"><code>tower-lsp</code></a> and its fork, <a href="https://crates.io/crates/lspower"><code>lspower</code></a>: implementations of the <a href="https://microsoft.github.io/language-server-protocol/">Language |
| Server Protocol</a> based on Tower.</li> |
| </ul> |
| <p>If you’re the maintainer of a crate that supports Tower, we’d love to add |
| your crate to this list! Please <a href="https://github.com/tower-rs/tower/compare">open a PR</a> adding a brief description of |
| your library!</p> |
| <h3 id="getting-started"><a href="#getting-started">Getting Started</a></h3> |
| <p>If you’re brand new to Tower and want to start with the basics, we recommend you |
| check out some of our <a href="https://github.com/tower-rs/tower/tree/master/guides">guides</a>.</p> |
| <p>The various middleware implementations provided by this crate are feature |
| flagged, so that users can only compile the parts of Tower they need. By |
| default, all the optional middleware are disabled.</p> |
| <p>To get started using all of Tower’s optional middleware, add this to your |
| <code>Cargo.toml</code>:</p> |
| <div class="example-wrap"><pre class="language-toml"><code>tower = { version = "0.4", features = ["full"] }</code></pre></div> |
| <p>Alternatively, you can only enable some features. For example, to enable |
| only the <a href="crate::retry"><code>retry</code></a> and <a href="timeout/index.html"><code>timeout</code></a> middleware, write:</p> |
| <div class="example-wrap"><pre class="language-toml"><code>tower = { version = "0.4", features = ["retry", "timeout"] }</code></pre></div> |
| <p>See <a href="#modules">here</a> for a complete list of all middleware provided by |
| Tower.</p> |
| <h3 id="supported-rust-versions"><a href="#supported-rust-versions">Supported Rust Versions</a></h3> |
| <p>Tower will keep a rolling MSRV (minimum supported Rust version) policy of <strong>at |
| least</strong> 6 months. When increasing the MSRV, the new Rust version must have been |
| released at least six months ago. The current MSRV is 1.49.0.</p> |
| </div></details><h2 id="modules" class="small-section-header"><a href="#modules">Modules</a></h2><div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="mod" href="balance/index.html" title="tower::balance mod">balance</a></div><div class="item-right docblock-short">Middleware that allows balancing load among multiple services.</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="buffer/index.html" title="tower::buffer mod">buffer</a></div><div class="item-right docblock-short">Middleware that provides a buffered mpsc channel to a service.</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="builder/index.html" title="tower::builder mod">builder</a></div><div class="item-right docblock-short">Builder types to compose layers and services</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="discover/index.html" title="tower::discover mod">discover</a></div><div class="item-right docblock-short">Service discovery</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="layer/index.html" title="tower::layer mod">layer</a></div><div class="item-right docblock-short">A collection of <a href="trait.Layer.html"><code>Layer</code></a> based tower services</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="limit/index.html" title="tower::limit mod">limit</a></div><div class="item-right docblock-short">Tower middleware for limiting requests.</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="load/index.html" title="tower::load mod">load</a></div><div class="item-right docblock-short">Service load measurement</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="make/index.html" title="tower::make mod">make</a></div><div class="item-right docblock-short">Trait aliases for Services that produce specific types of Responses.</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="ready_cache/index.html" title="tower::ready_cache mod">ready_cache</a></div><div class="item-right docblock-short">A cache of services</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="timeout/index.html" title="tower::timeout mod">timeout</a></div><div class="item-right docblock-short">Middleware that applies a timeout to requests.</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="util/index.html" title="tower::util mod">util</a></div><div class="item-right docblock-short">Various utility types and functions that are generally used with Tower.</div></div></div><h2 id="structs" class="small-section-header"><a href="#structs">Structs</a></h2><div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.ServiceBuilder.html" title="tower::ServiceBuilder struct">ServiceBuilder</a></div><div class="item-right docblock-short">Declaratively construct <a href="trait.Service.html"><code>Service</code></a> values.</div></div></div><h2 id="traits" class="small-section-header"><a href="#traits">Traits</a></h2><div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="trait" href="trait.Layer.html" title="tower::Layer trait">Layer</a></div><div class="item-right docblock-short">Decorates a <a href="https://docs.rs/tower/latest/tower/trait.Service.html"><code>Service</code></a>, transforming either the request or the response.</div></div><div class="item-row"><div class="item-left module-item"><a class="trait" href="trait.MakeService.html" title="tower::MakeService trait">MakeService</a></div><div class="item-right docblock-short">Creates new <a href="trait.Service.html" title="Service"><code>Service</code></a> values.</div></div><div class="item-row"><div class="item-left module-item"><a class="trait" href="trait.Service.html" title="tower::Service trait">Service</a></div><div class="item-right docblock-short">An asynchronous function from a <code>Request</code> to a <code>Response</code>.</div></div><div class="item-row"><div class="item-left module-item"><a class="trait" href="trait.ServiceExt.html" title="tower::ServiceExt trait">ServiceExt</a></div><div class="item-right docblock-short">An extension trait for <code>Service</code>s that provides a variety of convenient |
| adapters</div></div></div><h2 id="functions" class="small-section-header"><a href="#functions">Functions</a></h2><div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="fn" href="fn.service_fn.html" title="tower::service_fn fn">service_fn</a></div><div class="item-right docblock-short">Returns a new <a href="util/struct.ServiceFn.html" title="ServiceFn"><code>ServiceFn</code></a> with the given closure.</div></div></div><h2 id="types" class="small-section-header"><a href="#types">Type Definitions</a></h2><div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="type" href="type.BoxError.html" title="tower::BoxError type">BoxError</a></div><div class="item-right docblock-short">Alias for a type-erased error type.</div></div></div></section></div></main><div id="rustdoc-vars" data-root-path="../" data-current-crate="tower" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
