static function instance()
 {
     if (!isset(self::$instance)) {
         $class = __CLASS__;
         self::$instance = new $class();
     }
     return self::$instance;
 }
 function __construct($cache_connection, $cache_name, $file = false)
 {
     $this->cache_connection = $cache_connection;
     $this->cache_name = $cache_name;
     if ($file) {
         $logger = lmbCacheLogFile::instance($file);
     } else {
         $logger = lmbCacheLogMemory::instance();
     }
     $this->setLogger($logger);
 }