有次同事提出开发使用的MySQL数据库连接很慢，因为我们的MySQL开发数据库是单独一台机器部署的，所以认为可能是网络连接问题导致的。
在进行 ping和route后发现网络通信都是正常的，而且在MySQL机器上进行本地连接发现是很快的，所以网络问题基本上被排除了。以前也遇到过一次这样的问题，可后来就不知怎么突然好了，这次又遭遇这样的问题，所以想看看是不是MySQL的配置问题。在查询MySQL相关文档和网络搜索后，发现了一个配置似乎可以解决这样的问题，就是在MySQL的配置文件中增加如下配置参数：
[mysqld]
skip-name-resolve
在Linux下配置文件是/etc/my.cnf，在windows下配置文件是MySQL安装目录下的my.ini文件。注意该配置是加在 [mysqld]下面，在更改配置并保存后，然后重启mysql并远程连接测试，一切恢复如初。该参数的官方解释信息如下：
How MySQL uses DNS
When a new thread connects to mysqld, mysqld will spawn a new thread to handle the request. This thread will first check if the hostname is in the hostname cache. If not the thread will call gethostbyaddr_r() and gethostbyname_r() to resolve the hostname.
If the operating system doesn't support the above thread-safe calls, the thread will lock a mutex and call gethostbyaddr() and gethostbyname() instead. Note that in this case no other thread can resolve other hostnames that is not in the hostname cache until the first thread is ready.
You can disable DNS host lookup by starting mysqld with –skip-name-resolve. In this case you can however only use IP names in the MySQL privilege tables.
If you have a very slow DNS and many hosts, you can get more performance by either disabling DNS lookop with –skip-name-resolve or by increasing the HOST_CACHE_SIZE define (default: 128) and recompile mysqld.
You can disable the hostname cache with –skip-host-cache. You can clear the hostname cache with FLUSH HOSTS or mysqladmin flush-hosts.
If you don't want to allow connections over TCP/IP, you can do this by starting mysqld with –skip-networking.
