code: function(crontab) {
      let _config = this[$EXTRA];
      
      _config.logger.info(`Setting up cron schedule ${crontab}`);
  
      _config.job = new CronJob({
        cronTime: crontab,
        onTick: _.bind(co.wrap(this._cronCallback), this),
        start: true,
      });
  
      /* calculate and save time between runs */
      
      // we add 1 second to next date otherwise, _getNextDateFrom() returns 
      // the same date back
      let nextRunDate = _config.job.nextDate().add(1, 'seconds');
  
      _config.timeBetweenRunsMs = 
        _config.job.cronTime._getNextDateFrom(nextRunDate).valueOf() - nextRunDate.valueOf();
    }
docs: Start the cron scheduler for this job.