text: const log4js = require('log4js');
  log4js.configure(
    {
      appenders: {
        file: {
          type: 'file',
          filename: './log/AppLogFile.log',
          maxLogSize: 1024*1024*50 ,
          numBackups: 10, // keep five backup files
          compress: true, // compress the backups
          encoding: 'utf-8',
          mode: 0o0640,
          flags: 'w+'
        },
        dateFile: {
          type: 'dateFile',
          filename: './log/more-AppLogFile.log',
          pattern: 'yyyy-MM-dd-hh',
          compress: true
        },
        out: {
          type: 'stdout'
        }
      },
      categories: {
        default: { appenders: ['file', 'dateFile', 'out'], level: 'debug' }
      }
    }
  );
  
  const logger = log4js.getLogger('normal');
  const loggerApp = log4js.getLogger('application');
  const loggerSignaling = log4js.getLogger('signaling');
  
  
  exports.logger = function(){
  	var logger = log4js.getLogger('normal');
      return logger;
  }
  
  exports.loggerApp = function(){
  	var logger = log4js.getLogger('application');
  	logger.debug('debug');
  	logger.info('info');
  	logger.error('error');
  	logger.fatal('fatal');
  	logger.trace('trace');
      return logger;
  }
  
  exports.loggerSignaling = function(){
  	var logger = log4js.getLogger('signaling');
  	logger.debug('debug');
  	logger.info('info');
  	logger.error('error');
  	logger.fatal('fatal');
  	logger.trace('trace');
      return logger;
  }