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<li><a href="#default-pooling-configuration">Default pooling configuration
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<h1 id="connection-pooling" class="target">Connection pooling<a class="anchor" href="#connection-pooling" aria-hidden="true"><span class="glyphicon glyphicon-link"></span></a>
</h1>
<p>The driver maintains one or more connections opened to each Cassandra node selected by the load-balancing policy.
The amount of connections per host is defined in the pooling configuration.</p>
<h2 id="default-pooling-configuration" class="target">Default pooling configuration<a class="anchor" href="#default-pooling-configuration" aria-hidden="true"><span class="glyphicon glyphicon-link"></span></a>
</h2>
<p>The default number of connections per host depends on the version of the Cassandra cluster.</p>
<p>Cassandra versions 1.2 and 2.0 allow the clients to send up to <code>128</code> requests without waiting for a response per
connection. Higher versions of Cassandra ( that is 2.1 or greater) allow clients to send up to <code>32768</code> requests
without waiting for a response.</p>
<p>By default, the driver maintains two open connections to each host in the local datacenter and one to each host in a
remote datacenter for Cassandra 1.2 or 2.0 and one connection to each host (local or remote) for Cassandra 2.1 or
greater.</p>
<h2 id="setting-the-number-of-connections-per-host" class="target">Setting the number of connections per host<a class="anchor" href="#setting-the-number-of-connections-per-host" aria-hidden="true"><span class="glyphicon glyphicon-link"></span></a>
</h2>
<p>You can set the number of connections per host in the pooling configuration:</p>
<pre class="highlight"><code><span class="kr">const</span> <span class="nx">cassandra</span> <span class="o">=</span> <span class="nx">require</span><span class="p">(</span><span class="s1">'cassandra-driver'</span><span class="p">);</span>
<span class="kr">const</span> <span class="nx">distance</span> <span class="o">=</span> <span class="nx">cassandra</span><span class="p">.</span><span class="nx">types</span><span class="p">.</span><span class="nx">distance</span><span class="p">;</span>
<span class="kr">const</span> <span class="nx">options</span> <span class="o">=</span> <span class="p">{</span>
<span class="na">contactPoints</span><span class="p">:</span> <span class="p">[</span><span class="s1">'1.2.3.4'</span><span class="p">],</span>
<span class="na">pooling</span><span class="p">:</span> <span class="p">{</span>
<span class="na">coreConnectionsPerHost</span><span class="p">:</span> <span class="p">{</span>
<span class="p">[</span><span class="nx">distance</span><span class="p">.</span><span class="nx">local</span><span class="p">]</span> <span class="o">=</span> <span class="mi">2</span><span class="p">,</span>
<span class="p">[</span><span class="nx">distance</span><span class="p">.</span><span class="nx">remote</span><span class="p">]</span> <span class="o">=</span> <span class="mi">1</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="p">};</span>
<span class="kr">const</span> <span class="nx">client</span> <span class="o">=</span> <span class="k">new</span> <span class="nx">Client</span><span class="p">(</span><span class="nx">options</span><span class="p">);</span>
</code></pre>
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