How does Magento 2 detect whether it should use its database or filesystem to store the visitors sessions?

dmitry_fedyuk · May 8, 2017, 2:51pm

Context: How is the session initialized?

Magento\Framework\Session\SaveHandler::__construct()

magento/magento2/blob/2.1.6/lib/internal/Magento/Framework/Session/SaveHandler.php#L32-L61


/**
 * Constructor
 *
 * @param SaveHandlerFactory $saveHandlerFactory
 * @param DeploymentConfig $deploymentConfig
 * @param string $default
 */
public function __construct(
    SaveHandlerFactory $saveHandlerFactory,
    DeploymentConfig $deploymentConfig,
    $default = self::DEFAULT_HANDLER
) {
    /**
     * Session handler
     *
     * Save handler may be set to custom value in deployment config, which will override everything else.
     * Otherwise, try to read PHP settings for session.save_handler value. Otherwise, use 'files' as default.
     */
    $defaultSaveHandler = ini_get('session.save_handler') ?: SaveHandlerInterface::DEFAULT_HANDLER;
    $saveMethod = $deploymentConfig->get(Config::PARAM_SESSION_SAVE_METHOD, $defaultSaveHandler);
    $this->setSaveHandler($saveMethod);


    try {
        $connection = $saveHandlerFactory->create($saveMethod);
    } catch (SessionException $e) {
        $connection = $saveHandlerFactory->create($default);
        $this->setSaveHandler($default);
    }
    $this->saveHandlerAdapter = $connection;
}

Magento\Framework\Session\SaveHandlerInterface::DEFAULT_HANDLER

github.com

magento/magento2/blob/2.1.6/lib/internal/Magento/Framework/Session/SaveHandlerInterface.php#L12-L15


/**
 * Default session save handler
 */
const DEFAULT_HANDLER = 'files';