解决远程连接mysql很慢的⽅法（mysql_connect打开连
接慢）
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/myf，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
mysql下载starting the serverWhen 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.
根据⽂档说明，如果你的mysql主机查询DNS很慢或是有很多客户端主机时会导致连接很慢，由于我们的开发机器是不能够连接外⽹的，所以DNS解析是不可能完成的，从⽽也就明⽩了为什么连接那么慢了。同时，请注意在增加该配置参数
后，mysql的授权表中的host字段就不能够使⽤域名⽽只能够使⽤ ip地址了，因为这是禁⽌了域名解析的结果。

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