| <!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="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/tower-0.4.13/src/limit/concurrency/service.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>service.rs - source</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="../../../../source-script.js"></script><script defer src="../../../../source-files.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 source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><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></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../../tower/index.html"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></a><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="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="kw">use </span><span class="kw">super</span>::future::ResponseFuture; |
| <span class="kw">use </span>tokio::sync::{OwnedSemaphorePermit, Semaphore}; |
| <span class="kw">use </span>tokio_util::sync::PollSemaphore; |
| <span class="kw">use </span>tower_service::Service; |
| |
| <span class="kw">use </span>futures_core::ready; |
| <span class="kw">use </span>std::{ |
| sync::Arc, |
| task::{Context, Poll}, |
| }; |
| |
| <span class="doccomment">/// Enforces a limit on the concurrent number of requests the underlying |
| /// service can handle. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub struct </span>ConcurrencyLimit<T> { |
| inner: T, |
| semaphore: PollSemaphore, |
| <span class="doccomment">/// The currently acquired semaphore permit, if there is sufficient |
| /// concurrency to send a new request. |
| /// |
| /// The permit is acquired in `poll_ready`, and taken in `call` when sending |
| /// a new request. |
| </span>permit: <span class="prelude-ty">Option</span><OwnedSemaphorePermit>, |
| } |
| |
| <span class="kw">impl</span><T> ConcurrencyLimit<T> { |
| <span class="doccomment">/// Create a new concurrency limiter. |
| </span><span class="kw">pub fn </span>new(inner: T, max: usize) -> <span class="self">Self </span>{ |
| <span class="self">Self</span>::with_semaphore(inner, Arc::new(Semaphore::new(max))) |
| } |
| |
| <span class="doccomment">/// Create a new concurrency limiter with a provided shared semaphore |
| </span><span class="kw">pub fn </span>with_semaphore(inner: T, semaphore: Arc<Semaphore>) -> <span class="self">Self </span>{ |
| ConcurrencyLimit { |
| inner, |
| semaphore: PollSemaphore::new(semaphore), |
| permit: <span class="prelude-val">None</span>, |
| } |
| } |
| |
| <span class="doccomment">/// Get a reference to the inner service |
| </span><span class="kw">pub fn </span>get_ref(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span>T { |
| <span class="kw-2">&</span><span class="self">self</span>.inner |
| } |
| |
| <span class="doccomment">/// Get a mutable reference to the inner service |
| </span><span class="kw">pub fn </span>get_mut(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="kw-2">&mut </span>T { |
| <span class="kw-2">&mut </span><span class="self">self</span>.inner |
| } |
| |
| <span class="doccomment">/// Consume `self`, returning the inner service |
| </span><span class="kw">pub fn </span>into_inner(<span class="self">self</span>) -> T { |
| <span class="self">self</span>.inner |
| } |
| } |
| |
| <span class="kw">impl</span><S, Request> Service<Request> <span class="kw">for </span>ConcurrencyLimit<S> |
| <span class="kw">where |
| </span>S: Service<Request>, |
| { |
| <span class="kw">type </span>Response = S::Response; |
| <span class="kw">type </span>Error = S::Error; |
| <span class="kw">type </span>Future = ResponseFuture<S::Future>; |
| |
| <span class="kw">fn </span>poll_ready(<span class="kw-2">&mut </span><span class="self">self</span>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="prelude-ty">Result</span><(), <span class="self">Self</span>::Error>> { |
| <span class="comment">// If we haven't already acquired a permit from the semaphore, try to |
| // acquire one first. |
| </span><span class="kw">if </span><span class="self">self</span>.permit.is_none() { |
| <span class="self">self</span>.permit = <span class="macro">ready!</span>(<span class="self">self</span>.semaphore.poll_acquire(cx)); |
| <span class="macro">debug_assert!</span>( |
| <span class="self">self</span>.permit.is_some(), |
| <span class="string">"ConcurrencyLimit semaphore is never closed, so `poll_acquire` \ |
| should never fail"</span>, |
| ); |
| } |
| |
| <span class="comment">// Once we've acquired a permit (or if we already had one), poll the |
| // inner service. |
| </span><span class="self">self</span>.inner.poll_ready(cx) |
| } |
| |
| <span class="kw">fn </span>call(<span class="kw-2">&mut </span><span class="self">self</span>, request: Request) -> <span class="self">Self</span>::Future { |
| <span class="comment">// Take the permit |
| </span><span class="kw">let </span>permit = <span class="self">self |
| </span>.permit |
| .take() |
| .expect(<span class="string">"max requests in-flight; poll_ready must be called first"</span>); |
| |
| <span class="comment">// Call the inner service |
| </span><span class="kw">let </span>future = <span class="self">self</span>.inner.call(request); |
| |
| ResponseFuture::new(future, permit) |
| } |
| } |
| |
| <span class="kw">impl</span><T: Clone> Clone <span class="kw">for </span>ConcurrencyLimit<T> { |
| <span class="kw">fn </span>clone(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="self">Self </span>{ |
| <span class="comment">// Since we hold an `OwnedSemaphorePermit`, we can't derive `Clone`. |
| // Instead, when cloning the service, create a new service with the |
| // same semaphore, but with the permit in the un-acquired state. |
| </span><span class="self">Self </span>{ |
| inner: <span class="self">self</span>.inner.clone(), |
| semaphore: <span class="self">self</span>.semaphore.clone(), |
| permit: <span class="prelude-val">None</span>, |
| } |
| } |
| } |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"load"</span>)] |
| #[cfg_attr(docsrs, doc(cfg(feature = <span class="string">"load"</span>)))] |
| </span><span class="kw">impl</span><S> <span class="kw">crate</span>::load::Load <span class="kw">for </span>ConcurrencyLimit<S> |
| <span class="kw">where |
| </span>S: <span class="kw">crate</span>::load::Load, |
| { |
| <span class="kw">type </span>Metric = S::Metric; |
| <span class="kw">fn </span>load(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="self">Self</span>::Metric { |
| <span class="self">self</span>.inner.load() |
| } |
| } |
| </code></pre></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> |