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<title>Persistent Connections (version up to 1.1.4 *only*)</title>
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<h2 class="title">Persistent Connections (version up to 1.1.4 *only*)</h2>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
This section is not relevant for 1.2.0+. In 1.2.0+, connections are always
persistent and managed automatically by the driver. If you are using a
1.2.x release (but not 1.3.x or later), see
<a href="class.mongopool.html" class="classname">MongoPool</a> for more information on pooling.
</p>
</p></blockquote>
<p class="para">
Creating new connection to the database is very slow. To minimize the number
of connections that you need to make, you can use persistent connections. A
persistent connection is saved by PHP, so you can use the same connection for
multiple requests.
</p>
<p class="para">
For example, this simple program connects to the database 1000 times:
</p>
<div class="example" id="mongo.connecting.no-persistent-example">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br /></span><span style="color: #007700">for (</span><span style="color: #0000BB">$i</span><span style="color: #007700">=</span><span style="color: #0000BB">0</span><span style="color: #007700">; </span><span style="color: #0000BB">$i</span><span style="color: #007700"><</span><span style="color: #0000BB">1000</span><span style="color: #007700">; </span><span style="color: #0000BB">$i</span><span style="color: #007700">++) {<br /> </span><span style="color: #0000BB">$m </span><span style="color: #007700">= new </span><span style="color: #0000BB">MongoClient</span><span style="color: #007700">();<br />}<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
It takes approximately 18 seconds to execute. If we change it to use a
persistent connection:
</p>
<div class="example" id="mongo.connecting.persistent-example">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br /></span><span style="color: #007700">for (</span><span style="color: #0000BB">$i</span><span style="color: #007700">=</span><span style="color: #0000BB">0</span><span style="color: #007700">; </span><span style="color: #0000BB">$i</span><span style="color: #007700"><</span><span style="color: #0000BB">1000</span><span style="color: #007700">; </span><span style="color: #0000BB">$i</span><span style="color: #007700">++) {<br /> </span><span style="color: #0000BB">$m </span><span style="color: #007700">= new </span><span style="color: #0000BB">MongoClient</span><span style="color: #007700">(</span><span style="color: #DD0000">"localhost:27017"</span><span style="color: #007700">, array(</span><span style="color: #DD0000">"persist" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"x"</span><span style="color: #007700">));<br />}<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="para">
...it takes less than .02 seconds to execute, as it only makes one database
connection.
</p>
<p class="para">
Persistent connections need an identifier string (which is "x" in the above
example) to uniquely identify them. For a persistent connection to be used,
the hostname, port, persist string, and authentication credentials (username,
password and database, if given) must match an existing persistent
connection. Otherwise, a new connection will be created with this identifying
information.
</p>
<p class="para">
Persistent connections are <em class="emphasis">highly recommended</em> and should
always be used in production unless there is a compelling reason not to.
Most of the reasons that they are not recommended for relational databases
are irrelevant to MongoDB.
</p>
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