def set_filename(filename, shift_age=7, shift_size=1048576)
      logger = Logger.new(filename, shift_age, shift_size)
      logger.level = @logger.level
      logger.formatter = @logger.formatter
      @logger = logger
    end
def set_filename(filename, shift_age=7, shift_size=1048576)
      logger = Logger.new(filename, shift_age, shift_size)
      logger.level = @logger.level
      logger.formatter = @logger.formatter
      @logger = logger
    end
Creates a new Logger to write log messages to using the parameters
 specified. This method is executed asynchronously.
 @param [String] filename filename of active log file
 @param [Fixmun] shift_age maximum number of archive files to save
 @param [Fixmun] shift_size maximum file size