[Warning] IP address '123.123.123.123' could not be resolved: Name or service not known

오류 :

[Warning] IP address '123.123.123.123' could not be resolved: Name or service not known

증상 : 성능저하 및 mysql 데몬 죽음

이유 : 
외부에서 MySQL 서버에 연결 요청을 하면, MySQL 서버는 DNS를 통해 해당 호스트를 확인하고, 
이를 재사용하기 위해 performance_schema.host_cache에 저장한다.
이 과정에서 지연이 발생할 수 있는데 이때 연결 수가 초과되어 MySQL 데몬이 죽을 수 있다.

해결 :
my.cnf [mysqld] 부분에 skip-name-resolve를 추가하고 재시작하면 된다.

확인 : 
show variables like 'skip_name_resolve';

+-------------------+-------+
| Variable_name     | Value |
+-------------------+-------+
| skip_name_resolve | ON    |
+-------------------+-------+