the server will replace original request netloc with data_api automatically,
1) ordered url parameters and get redis key: get_hash_id(url)
2) get value:data in redis, if exists, then return value; if not, then request 
   data_api to get fresh value, save in redis by key and return

1. use mysql as cache middleware: set mysql info in `cacheserver::setting.py`.
2. use redis as cache middleware: change redis server host:port in `config.py`