docs: function BackendStorage (gateway, opts){
      
      // prepare ourself to make debug possible
      this.debug=opts.mysql.debug || opts.debug;
      this.gateway =gateway;
      this.count=0;  // stat for connection retry
      
      this.opts= {
              host     : opts.mysql.hostname || "localhost",
              user     : opts.mysql.username,
              password : opts.mysql.password,
              database : opts.mysql.basename || opts.username
      };  
      this.uid ="mysql:" + opts.mysql.username + "@" + opts.mysql.hostname + "/" + opts.mysql.basename;
      this.event = new EventEmitter();
      // create initial connection handler to database
      CreateConnection (this);
  }