<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <title>Create a new ReadPreference</title> </head> <body><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="mongodb-driver-readpreference.bsonserialize.html">MongoDB\Driver\ReadPreference::bsonSerialize</a></div> <div class="next" style="text-align: right; float: right;"><a href="mongodb-driver-readpreference.getmaxstalenessseconds.html">MongoDB\Driver\ReadPreference::getMaxStalenessSeconds</a></div> <div class="up"><a href="class.mongodb-driver-readpreference.html">MongoDB\Driver\ReadPreference</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div><hr /><div id="mongodb-driver-readpreference.construct" class="refentry"> <div class="refnamediv"> <h1 class="refname">MongoDB\Driver\ReadPreference::__construct</h1> <p class="verinfo">(mongodb >=1.0.0)</p><p class="refpurpose"><span class="refname">MongoDB\Driver\ReadPreference::__construct</span> — <span class="dc-title">Create a new ReadPreference</span></p> </div> <div class="refsect1 description" id="refsect1-mongodb-driver-readpreference.construct-description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="modifier">final</span> <span class="modifier">public</span> <span class="methodname"><strong>MongoDB\Driver\ReadPreference::__construct</strong></span> ( <span class="methodparam"><span class="type"><span class="type string|integer">string|integer</span></span> <code class="parameter">$mode</code></span> [, <span class="methodparam"><span class="type">array</span> <code class="parameter">$tagSets</code><span class="initializer"> = <strong><code>NULL</code></strong></span></span> [, <span class="methodparam"><span class="type">array</span> <code class="parameter">$options</code><span class="initializer"> = array()</span></span> ]] )</div> <p class="para rdfs-comment"> Constructs a new <a href="class.mongodb-driver-readpreference.html" class="classname">MongoDB\Driver\ReadPreference</a>, which is an immutable value object. </p> </div> <div class="refsect1 parameters" id="refsect1-mongodb-driver-readpreference.construct-parameters"> <h3 class="title">Parameters</h3> <dl> <dt> <code class="parameter">mode</code></dt> <dd> <p class="para"> <table class="doctable table"> <caption><strong>Read preference mode</strong></caption> <thead> <tr> <th>Value</th> <th>Description</th> </tr> </thead> <tbody class="tbody"> <tr> <td><strong><code>MongoDB\Driver\ReadPreference::RP_PRIMARY</code></strong> or <em>"primary"</em></td> <td> <p class="para"> All operations read from the current replica set primary. This is the default read preference for MongoDB. </p> </td> </tr> <tr> <td><strong><code>MongoDB\Driver\ReadPreference::RP_PRIMARY_PREFERRED</code></strong> or <em>"primaryPreferred"</em></td> <td> <p class="para"> In most situations, operations read from the primary but if it is unavailable, operations read from secondary members. </p> </td> </tr> <tr> <td><strong><code>MongoDB\Driver\ReadPreference::RP_SECONDARY</code></strong> or <em>"secondary"</em></td> <td> <p class="para"> All operations read from the secondary members of the replica set. </p> </td> </tr> <tr> <td><strong><code>MongoDB\Driver\ReadPreference::RP_SECONDARY_PREFERRED</code></strong> or <em>"secondaryPreferred"</em></td> <td> <p class="para"> In most situations, operations read from secondary members but if no secondary members are available, operations read from the primary. </p> </td> </tr> <tr> <td><strong><code>MongoDB\Driver\ReadPreference::RP_NEAREST</code></strong> or <em>"nearest"</em></td> <td> <p class="para"> Operations read from member of the replica set with the least network latency, irrespective of the member's type. </p> </td> </tr> </tbody> </table> </p> </dd> <dt> <code class="parameter">tagSets</code></dt> <dd> <p class="para"> Tag sets allow you to target read operations to specific members of a replica set. This parameter should be an array of associative arrays, each of which contain zero or more key/value pairs. When selecting a server for a read operation, the driver attempt to select a node having all tags in a set (i.e. the associative array of key/value pairs). If selection fails, the driver will attempt subsequent sets. An empty tag set (<em>array()</em>) will match any node and may be used as a fallback. </p> <p class="para"> Tags are not compatible with the <strong><code>MongoDB\Driver\ReadPreference::RP_PRIMARY</code></strong> mode and, in general, only apply when selecting a secondary member of a set for a read operation. However, the <strong><code>MongoDB\Driver\ReadPreference::RP_NEAREST</code></strong> mode, when combined with a tag set, selects the matching member with the lowest network latency. This member may be a primary or secondary. </p> </dd> <dt> <code class="parameter">options</code></dt> <dd> <p class="para"> <table class="doctable table"> <caption><strong>options</strong></caption> <thead> <tr> <th>Option</th> <th>Type</th> <th>Description</th> </tr> </thead> <tbody class="tbody"> <tr> <td>maxStalenessSeconds</td> <td><span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span></td> <td> <p class="para"> Specifies a maximum replication lag, or "staleness", for reads from secondaries. When a secondary's estimated staleness exceeds this value, the driver stops using it for read operations. </p> <p class="para"> If specified, the max staleness must be a signed 32-bit integer greater than or equal to <strong><code>MongoDB\Driver\ReadPreference::SMALLEST_MAX_STALENESS_SECONDS</code></strong>. </p> <p class="para"> Defaults to <strong><code>MongoDB\Driver\ReadPreference::NO_MAX_STALENESS</code></strong>, which means that the driver will not consider a secondary's lag when choosing where to direct a read operation. </p> <p class="para"> This option is not compatible with the <strong><code>MongoDB\Driver\ReadPreference::RP_PRIMARY</code></strong> mode. Specifying a max staleness also requires all MongoDB instances in the deployment to be using MongoDB 3.4+. An exception will be thrown at execution time if any MongoDB instances in the deployment are of an older server version. </p> </td> </tr> </tbody> </table> </p> </dd> </dl> </div> <div class="refsect1 errors" id="refsect1-mongodb-driver-readpreference.construct-errors"> <h3 class="title">Errors/Exceptions</h3> <ul class="simplelist"> <li class="member">Throws <a href="class.mongodb-driver-exception-invalidargumentexception.html" class="classname">MongoDB\Driver\Exception\InvalidArgumentException</a> on argument parsing errors.</li> <li class="member">Throws <a href="class.mongodb-driver-exception-invalidargumentexception.html" class="classname">MongoDB\Driver\Exception\InvalidArgumentException</a> if <code class="parameter">mode</code> is invalid.</li> <li class="member">Throws <a href="class.mongodb-driver-exception-invalidargumentexception.html" class="classname">MongoDB\Driver\Exception\InvalidArgumentException</a> if <code class="parameter">tagSets</code> is provided for a primary read preference or is malformed (i.e. not an array of zero or more documents).</li> <li class="member">Throws <a href="class.mongodb-driver-exception-invalidargumentexception.html" class="classname">MongoDB\Driver\Exception\InvalidArgumentException</a> if the <em>"maxStalenessSeconds"</em> option is provided for a primary read preference or is out of range.</li> </ul> </div> <div class="refsect1 changelog" id="refsect1-mongodb-driver-readpreference.construct-changelog"> <h3 class="title">Changelog</h3> <p class="para"> <table class="doctable informaltable"> <thead> <tr> <th>Version</th> <th>Description</th> </tr> </thead> <tbody class="tbody"> <tr> <td>1.3.0</td> <td> <p class="para"> The <code class="parameter">mode</code> argument now accepts a string value, which is consistent with the <em>"readPreference"</em> URI option for <span class="function"><a href="mongodb-driver-manager.construct.html" class="function">MongoDB\Driver\Manager::__construct()</a></span>. </p> </td> </tr> <tr> <td>1.2.0</td> <td> <p class="para"> Added a third <code class="parameter">options</code> argument, which supports the <em>"maxStalenessSeconds"</em> option. </p> </td> </tr> </tbody> </table> </p> </div> <div class="refsect1 examples" id="refsect1-mongodb-driver-readpreference.construct-examples"> <h3 class="title">Examples</h3> <div class="example" id="example-1713"> <p><strong>Example #1 <span class="function"><strong>MongoDB\Driver\ReadPreference::__construct()</strong></span> example</strong></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"> <span style="color: #0000BB"><?php<br /><br /></span><span style="color: #FF8000">/* Prefer a secondary node but fall back to a primary. */<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(new </span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">ReadPreference</span><span style="color: #007700">(</span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">ReadPreference</span><span style="color: #007700">::</span><span style="color: #0000BB">RP_SECONDARY_PREFERRED</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">/* Prefer a node in the New York data center with lowest latency. */<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(new </span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">ReadPreference</span><span style="color: #007700">(</span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">ReadPreference</span><span style="color: #007700">::</span><span style="color: #0000BB">RP_NEAREST</span><span style="color: #007700">, [[</span><span style="color: #DD0000">'dc' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'ny'</span><span style="color: #007700">]]));<br /><br /></span><span style="color: #FF8000">/* Require a secondary node whose replication lag is within two minutes of the primary */<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(new </span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">ReadPreference</span><span style="color: #007700">(</span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">ReadPreference</span><span style="color: #007700">::</span><span style="color: #0000BB">RP_SECONDARY</span><span style="color: #007700">, </span><span style="color: #0000BB">null</span><span style="color: #007700">, [</span><span style="color: #DD0000">'maxStalenessSeconds' </span><span style="color: #007700">=> </span><span style="color: #0000BB">120</span><span style="color: #007700">]));<br /><br /></span><span style="color: #0000BB">?></span> </span> </code></div> </div> <div class="example-contents"><p>The above example will output:</p></div> <div class="example-contents screen"> <div class="cdata"><pre> object(MongoDB\Driver\ReadPreference)#1 (1) { ["mode"]=> string(18) "secondaryPreferred" } object(MongoDB\Driver\ReadPreference)#1 (2) { ["mode"]=> string(7) "nearest" ["tags"]=> array(1) { [0]=> object(stdClass)#2 (1) { ["dc"]=> string(2) "ny" } } } object(MongoDB\Driver\ReadPreference)#1 (2) { ["mode"]=> string(9) "secondary" ["maxStalenessSeconds"]=> int(120) } </pre></div> </div> </div> </div> <div class="refsect1 seealso" id="refsect1-mongodb-driver-readpreference.construct-seealso"> <h3 class="title">See Also</h3> <ul class="simplelist"> <li class="member"><a href="https://docs.mongodb.com/manual/core/read-preference/" class="link external">» Read Preference reference</a></li> </ul> </div> </div><hr /><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="mongodb-driver-readpreference.bsonserialize.html">MongoDB\Driver\ReadPreference::bsonSerialize</a></div> <div class="next" style="text-align: right; float: right;"><a href="mongodb-driver-readpreference.getmaxstalenessseconds.html">MongoDB\Driver\ReadPreference::getMaxStalenessSeconds</a></div> <div class="up"><a href="class.mongodb-driver-readpreference.html">MongoDB\Driver\ReadPreference</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> 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