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<!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="API documentation for the Rust `mpsc` mod in crate `tokio`."><meta name="keywords" content="rust, rustlang, rust-lang, mpsc"><title>tokio::sync::mpsc - Rust</title><link rel="stylesheet" type="text/css" href="../../../normalize.css"><link rel="stylesheet" type="text/css" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../../light.css" id="themeStyle"><link rel="stylesheet" type="text/css" href="../../../dark.css" disabled ><link rel="stylesheet" type="text/css" href="../../../ayu.css" disabled ><script id="default-settings"></script><script src="../../../storage.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="icon" type="image/svg+xml" href="../../../favicon.svg">
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<link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><style type="text/css">#crate-search{background-image:url("../../../down-arrow.svg");}</style></head><body class="rustdoc mod"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../../tokio/index.html'><div class='logo-container rust-logo'><img src='../../../rust-logo.png' alt='logo'></div></a><p class="location">Module mpsc</p><div class="sidebar-elems"><div class="block items"><ul><li><a href="#modules">Modules</a></li><li><a href="#structs">Structs</a></li><li><a href="#functions">Functions</a></li></ul></div><p class="location"><a href="../../index.html">tokio</a>::<wbr><a href="../index.html">sync</a></p><script>window.sidebarCurrent = {name: "mpsc", ty: "mod", relpath: "../"};</script><script defer src="../sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu"><img src="../../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices" role="menu"></div></div><script src="../../../theme.js"></script><nav class="sub"><form class="search-form"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" disabled autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><button type="button" class="help-button">?</button>
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<a id="settings-menu" href="../../../settings.html"><img src="../../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class="fqn"><span class="out-of-band"><span id="render-detail"><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span><a class="srclink" href="../../../src/tokio/sync/mpsc/mod.rs.html#1-98" title="goto source code">[src]</a></span><span class="in-band">Module <a href="../../index.html">tokio</a>::<wbr><a href="../index.html">sync</a>::<wbr><a class="mod" href="">mpsc</a></span></h1><div class="docblock"><p>A multi-producer, single-consumer queue for sending values between
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asynchronous tasks.</p>
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<p>This module provides two variants of the channel: bounded and unbounded. The
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bounded variant has a limit on the number of messages that the channel can
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store, and if this limit is reached, trying to send another message will
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wait until a message is received from the channel. An unbounded channel has
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an infinite capacity, so the <code>send</code> method will always complete immediately.
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This makes the <a href="../../../tokio/sync/mpsc/struct.UnboundedSender.html"><code>UnboundedSender</code></a> usable from both synchronous and
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asynchronous code.</p>
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<p>Similar to the <code>mpsc</code> channels provided by <code>std</code>, the channel constructor
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functions provide separate send and receive handles, <a href="../../../tokio/sync/mpsc/struct.Sender.html"><code>Sender</code></a> and
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<a href="../../../tokio/sync/mpsc/struct.Receiver.html"><code>Receiver</code></a> for the bounded channel, <a href="../../../tokio/sync/mpsc/struct.UnboundedSender.html"><code>UnboundedSender</code></a> and
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<a href="../../../tokio/sync/mpsc/struct.UnboundedReceiver.html"><code>UnboundedReceiver</code></a> for the unbounded channel. If there is no message to read,
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the current task will be notified when a new value is sent. <a href="../../../tokio/sync/mpsc/struct.Sender.html"><code>Sender</code></a> and
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<a href="../../../tokio/sync/mpsc/struct.UnboundedSender.html"><code>UnboundedSender</code></a> allow sending values into the channel. If the bounded
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channel is at capacity, the send is rejected and the task will be notified
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when additional capacity is available. In other words, the channel provides
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backpressure.</p>
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<h1 id="disconnection" class="section-header"><a href="#disconnection">Disconnection</a></h1>
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<p>When all <a href="../../../tokio/sync/mpsc/struct.Sender.html"><code>Sender</code></a> handles have been dropped, it is no longer
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possible to send values into the channel. This is considered the termination
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event of the stream. As such, <code>Receiver::poll</code> returns <code>Ok(Ready(None))</code>.</p>
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<p>If the <a href="../../../tokio/sync/mpsc/struct.Receiver.html"><code>Receiver</code></a> handle is dropped, then messages can no longer
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be read out of the channel. In this case, all further attempts to send will
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result in an error.</p>
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<h1 id="clean-shutdown" class="section-header"><a href="#clean-shutdown">Clean Shutdown</a></h1>
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<p>When the <a href="../../../tokio/sync/mpsc/struct.Receiver.html"><code>Receiver</code></a> is dropped, it is possible for unprocessed messages to
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remain in the channel. Instead, it is usually desirable to perform a "clean"
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shutdown. To do this, the receiver first calls <code>close</code>, which will prevent
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any further messages to be sent into the channel. Then, the receiver
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consumes the channel to completion, at which point the receiver can be
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dropped.</p>
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<h1 id="communicating-between-sync-and-async-code" class="section-header"><a href="#communicating-between-sync-and-async-code">Communicating between sync and async code</a></h1>
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<p>When you want to communicate between synchronous and asynchronous code, there
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are two situations to consider:</p>
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<p><strong>Bounded channel</strong>: If you need a bounded channel, you should use a bounded
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Tokio <code>mpsc</code> channel for both directions of communication. Instead of calling
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the async <a href="../../../tokio/sync/mpsc/struct.Sender.html#method.send"><code>send</code></a> or <a href="../../../tokio/sync/mpsc/struct.Receiver.html#method.recv"><code>recv</code></a> methods, in
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synchronous code you will need to use the <a href="../../../tokio/sync/mpsc/struct.Sender.html#method.blocking_send"><code>blocking_send</code></a> or
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<a href="../../../tokio/sync/mpsc/struct.Receiver.html#method.blocking_recv"><code>blocking_recv</code></a> methods.</p>
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<p><strong>Unbounded channel</strong>: You should use the kind of channel that matches where
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the receiver is. So for sending a message <em>from async to sync</em>, you should
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use <a href="https://doc.rust-lang.org/nightly/std/sync/mpsc/fn.channel.html">the standard library unbounded channel</a> or
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<a href="https://docs.rs/crossbeam/*/crossbeam/channel/fn.unbounded.html">crossbeam</a>. Similarly, for sending a message <em>from sync
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to async</em>, you should use an unbounded Tokio <code>mpsc</code> channel.</p>
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</div><h2 id="modules" class="section-header"><a href="#modules">Modules</a></h2>
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<table><tr class="module-item"><td><a class="mod" href="error/index.html" title="tokio::sync::mpsc::error mod">error</a></td><td class="docblock-short"><p>Channel error types</p>
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</td></tr></table><h2 id="structs" class="section-header"><a href="#structs">Structs</a></h2>
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<table><tr class="module-item"><td><a class="struct" href="struct.Permit.html" title="tokio::sync::mpsc::Permit struct">Permit</a></td><td class="docblock-short"><p>Permit to send one value into the channel.</p>
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</td></tr><tr class="module-item"><td><a class="struct" href="struct.Receiver.html" title="tokio::sync::mpsc::Receiver struct">Receiver</a></td><td class="docblock-short"><p>Receive values from the associated <code>Sender</code>.</p>
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</td></tr><tr class="module-item"><td><a class="struct" href="struct.Sender.html" title="tokio::sync::mpsc::Sender struct">Sender</a></td><td class="docblock-short"><p>Send values to the associated <code>Receiver</code>.</p>
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</td></tr><tr class="module-item"><td><a class="struct" href="struct.UnboundedReceiver.html" title="tokio::sync::mpsc::UnboundedReceiver struct">UnboundedReceiver</a></td><td class="docblock-short"><p>Receive values from the associated <code>UnboundedSender</code>.</p>
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</td></tr><tr class="module-item"><td><a class="struct" href="struct.UnboundedSender.html" title="tokio::sync::mpsc::UnboundedSender struct">UnboundedSender</a></td><td class="docblock-short"><p>Send values to the associated <code>UnboundedReceiver</code>.</p>
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</td></tr></table><h2 id="functions" class="section-header"><a href="#functions">Functions</a></h2>
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<table><tr class="module-item"><td><a class="fn" href="fn.channel.html" title="tokio::sync::mpsc::channel fn">channel</a></td><td class="docblock-short"><p>Creates a bounded mpsc channel for communicating between asynchronous tasks
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with backpressure.</p>
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</td></tr><tr class="module-item"><td><a class="fn" href="fn.unbounded_channel.html" title="tokio::sync::mpsc::unbounded_channel fn">unbounded_channel</a></td><td class="docblock-short"><p>Creates an unbounded mpsc channel for communicating between asynchronous
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tasks without backpressure.</p>
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</td></tr></table></section><section id="search" class="content hidden"></section><section class="footer"></section><script>window.rootPath = "../../../";window.currentCrate = "tokio";</script><script src="../../../main.js"></script><script defer src="../../../search-index.js"></script></body></html> |