今早发现mysql日志中有非常多例如以下的警告:
140724 18:41:25 [Warning] IP address '172.16.18.217' could not be resolved: Temporary failure in name resolution 140724 18:41:25 [Warning] IP address '172.16.18.217' could not be resolved: Temporary failure in name resolution 140724 18:41:26 [Warning] IP address '172.16.18.217' could not be resolved: Temporary failure in name resolution 140724 18:41:26 [Warning] IP address '172.16.18.217' could not be resolved: Temporary failure in name resolution 140724 18:41:27 [Warning] IP address '172.16.18.217' could not be resolved: Temporary failure in name resolution 140724 18:41:28 [Warning] IP address '172.16.18.217' could not be resolved: Temporary failure in name resolution 140724 18:41:28 [Warning] IP address '172.16.18.217' could not be resolved: Temporary failure in name resolution 140724 18:41:28 [Warning] IP address '172.16.18.217' could not be resolved: Temporary failure in name resolution 140724 18:41:28 [Warning] IP address '172.16.18.217' could not be resolved: Temporary failure in name resolution 140724 18:44:54 [Warning] IP address '61.143.209.110' could not be resolved: Temporary failure in name resolution 140724 18:44:54 [Warning] IP address '61.143.209.110' could not be resolved: Temporary failure in name resolution 140724 18:44:54 [Warning] IP address '61.143.209.110' could not be resolved: Temporary failure in name resolution 140724 18:44:54 [Warning] IP address '61.143.209.110' could not be resolved: Temporary failure in name resolution 140724 18:44:54 [Warning] IP address '61.143.209.110' could not be resolved: Temporary failure in name resolution 140724 18:44:55 [Warning] IP address '61.143.209.110' could not be resolved: Temporary failure in name resolution 140724 18:44:55 [Warning] IP address '61.143.209.110' could not be resolved: Temporary failure in name resolution 140724 18:44:55 [Warning] IP address '61.143.209.110' could not be resolved: Temporary failure in name resolution 140724 18:44:55 [Warning] IP address '61.143.209.110' could not be resolved: Temporary failure in name resolution
问题产生的原因: 出现错误的原因是MYSQL Server在本地内存中维护了一个非本地的Client TCP cache。这个cache中包括了远程Client的登录信息,比方IP地址。hostname等信息。 假设Client连接到server后,Mysql首先会在本地TCP池中依据IP地址解析client的hostname或者反解析,假设解析不到。就会去DNS中进行解析,假设还是解析失败 就是在error log中写入这种警告信息。 解决的办法: 1.能够通过两个參数来disable这个功能,在MYSQL的配置文件里[mysqld]中增加以下的參数: [mysqld] --skip-host-cache --skip-name-resolve 又一次授权,将全部訪问数据库server的授权方式都改成IP形式的。 grant all on *.* to ‘root’@’172.16.12.68’identified by ‘123456’; 2.加入授权。 将全部訪问数据库server的授权方式都改成IP形式。 不同的用户用不同的username和password。
grant all on *.* to ‘user_68’@’172.16.12.68’identified by ‘pwd_68’; grant all on *.* to ‘user_67’@’172.16.12.67’identified by ‘pwd_67’; .... 然后去 mysql数据库以下的 user表 和db表 以下删除掉那些含有含有主机名字的权限记录。 总结: 1.要么加上 --skip-host-cache --skip-name-resolve 使得MySQL将不再通过DNS解析地址。 2.要么在赋予权限的时候 直接用ip地址,去掉那些用主机名字的权限。