Limit Session Metadata Writes

The default behavior of PHP session is to persist the session regardless of whether the session data has changed or not. In Symfony, each time the session is accessed, metadata is recorded (session created/last used) which can be used to determine session age and idle time.

If for performance reasons you wish to limit the frequency at which the session persists, this feature can adjust the granularity of the metadata updates and persist the session less often while still maintaining relatively accurate metadata. If other session data is changed, the session will always persist.

You can tell Symfony not to update the metadata "session last updated" time until a certain amount of time has passed, by setting framework.session.metadata_update_threshold to a value in seconds greater than zero:

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framework:
    session:
        metadata_update_threshold: 120

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<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:framework="http://symfony.com/schema/dic/symfony"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd
        http://symfony.com/schema/dic/symfony http://symfony.com/schema/dic/symfony/symfony-1.0.xsd">

    <framework:config>
        <framework:session metadata-update-threshold="120" />
    </framework:config>

</container>

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$container->loadFromExtension('framework', array(
    'session' => array(
        'metadata_update_threshold' => 120,
    ),
));