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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="A generic connection pool."><meta name="keywords" content="rust, rustlang, rust-lang, r2d2"><title>r2d2 - 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" type="text/css" href="../normalize.css"><link rel="stylesheet" type="text/css" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../ayu.css" disabled><link rel="stylesheet" type="text/css" href="../dark.css" disabled><link rel="stylesheet" type="text/css" 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">&#9776;</button><a class="sidebar-logo" href="../r2d2/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div>
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        </a><h2 class="location"><a href="#">Crate r2d2</a></h2><div class="sidebar-elems"><div class="block"><ul><li class="version">Version 0.8.10</li><li><a id="all-types" href="all.html">All Items</a></li></ul></div><section><div class="block"><ul><li><a href="#reexports">Re-exports</a></li><li><a href="#modules">Modules</a></li><li><a href="#structs">Structs</a></li><li><a href="#traits">Traits</a></li></ul></div></section></div></nav><main><div class="width-limiter"><div class="sub-container"><a class="sub-logo-container" href="../r2d2/index.html"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></a><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"><button type="button">?</button></div><div id="settings-menu" tabindex="-1">
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    <h1 class="fqn"><span class="in-band">Crate <a class="mod" href="#">r2d2</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></span></h1><span class="out-of-band"><a class="srclink" href="../src/r2d2/lib.rs.html#1-653">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">&#x2212;</span>]</a></span></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>A generic connection pool.</p>
<p>Opening a new database connection every time one is needed is both
inefficient and can lead to resource exhaustion under high traffic
conditions. A connection pool maintains a set of open connections to a
database, handing them out for repeated use.</p>
<p>r2d2 is agnostic to the connection type it is managing. Implementors of the
<code>ManageConnection</code> trait provide the database-specific logic to create and
check the health of connections.</p>
<h2 id="example"><a href="#example">Example</a></h2>
<p>Using an imaginary “foodb” database.</p>

<div class='information'><div class='tooltip ignore'>ⓘ</div></div><div class="example-wrap"><pre class="rust rust-example-rendered ignore"><code><span class="kw">use</span> <span class="ident">std::thread</span>;

<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">r2d2</span>;
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">r2d2_foodb</span>;

<span class="kw">fn</span> <span class="ident">main</span>() {
    <span class="kw">let</span> <span class="ident">manager</span> <span class="op">=</span> <span class="ident">r2d2_foodb::FooConnectionManager::new</span>(<span class="string">&quot;localhost:1234&quot;</span>);
    <span class="kw">let</span> <span class="ident">pool</span> <span class="op">=</span> <span class="ident">r2d2::Pool::builder</span>()
        .<span class="ident">max_size</span>(<span class="number">15</span>)
        .<span class="ident">build</span>(<span class="ident">manager</span>)
        .<span class="ident">unwrap</span>();

    <span class="kw">for</span> <span class="kw">_</span> <span class="kw">in</span> <span class="number">0</span>..<span class="number">20</span> {
        <span class="kw">let</span> <span class="ident">pool</span> <span class="op">=</span> <span class="ident">pool</span>.<span class="ident">clone</span>();
        <span class="ident">thread::spawn</span>(<span class="kw">move</span> <span class="op">|</span><span class="op">|</span> {
            <span class="kw">let</span> <span class="ident">conn</span> <span class="op">=</span> <span class="ident">pool</span>.<span class="ident">get</span>().<span class="ident">unwrap</span>();
            <span class="comment">// use the connection</span>
            <span class="comment">// it will be returned to the pool when it falls out of scope.</span>
        })
    }
}</code></pre></div>
</div></details><h2 id="reexports" class="small-section-header"><a href="#reexports">Re-exports</a></h2>
<div class="item-table"><div class="item-row"><div class="item-left import-item" id="reexport.HandleEvent"><code>pub use crate::event::<a class="trait" href="event/trait.HandleEvent.html" title="trait r2d2::event::HandleEvent">HandleEvent</a>;</code></div><div class="item-right docblock-short"></div></div><div class="item-row"><div class="item-left import-item" id="reexport.NopEventHandler"><code>pub use crate::event::<a class="struct" href="event/struct.NopEventHandler.html" title="struct r2d2::event::NopEventHandler">NopEventHandler</a>;</code></div><div class="item-right docblock-short"></div></div></div><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="event/index.html" title="r2d2::event mod">event</a></div><div class="item-right docblock-short"><p>Event subscriptions.</p>
</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.Builder.html" title="r2d2::Builder struct">Builder</a></div><div class="item-right docblock-short"><p>A builder for a connection pool.</p>
</div></div><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.Error.html" title="r2d2::Error struct">Error</a></div><div class="item-right docblock-short"><p>The error type returned by methods in this crate.</p>
</div></div><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.Extensions.html" title="r2d2::Extensions struct">Extensions</a></div><div class="item-right docblock-short"><p>A “type map” used to associate data with pooled connections.</p>
</div></div><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.LoggingErrorHandler.html" title="r2d2::LoggingErrorHandler struct">LoggingErrorHandler</a></div><div class="item-right docblock-short"><p>A <code>HandleError</code> implementation which logs at the error level.</p>
</div></div><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.NopConnectionCustomizer.html" title="r2d2::NopConnectionCustomizer struct">NopConnectionCustomizer</a></div><div class="item-right docblock-short"><p>A <code>CustomizeConnection</code> which does nothing.</p>
</div></div><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.NopErrorHandler.html" title="r2d2::NopErrorHandler struct">NopErrorHandler</a></div><div class="item-right docblock-short"><p>A <code>HandleError</code> implementation which does nothing.</p>
</div></div><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.Pool.html" title="r2d2::Pool struct">Pool</a></div><div class="item-right docblock-short"><p>A generic connection pool.</p>
</div></div><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.PooledConnection.html" title="r2d2::PooledConnection struct">PooledConnection</a></div><div class="item-right docblock-short"><p>A smart pointer wrapping a connection.</p>
</div></div><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.State.html" title="r2d2::State struct">State</a></div><div class="item-right docblock-short"><p>Information about the state of a <code>Pool</code>.</p>
</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.CustomizeConnection.html" title="r2d2::CustomizeConnection trait">CustomizeConnection</a></div><div class="item-right docblock-short"><p>A trait which allows for customization of connections.</p>
</div></div><div class="item-row"><div class="item-left module-item"><a class="trait" href="trait.HandleError.html" title="r2d2::HandleError trait">HandleError</a></div><div class="item-right docblock-short"><p>A trait which handles errors reported by the <code>ManageConnection</code>.</p>
</div></div><div class="item-row"><div class="item-left module-item"><a class="trait" href="trait.ManageConnection.html" title="r2d2::ManageConnection trait">ManageConnection</a></div><div class="item-right docblock-short"><p>A trait which provides connection-specific functionality.</p>
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