'initial redis client object'

def init_redis(self, host='localhost', port=6379, db=0, key_wait='spider.wait', key_all='spider.all'):

    if (not self._redis_client):
        self._redis_client = redis.Redis(host=host, port=port, db=db)
        self._key_wait = key_wait
        self._key_all = key_all
    return
