遠端連線MySQL速度慢的解決辦法

skip-name-resolve

 

現象：

Windows 2003下的MySQL 5伺服器，本機串連到MySQL服務非常快，區域網路內有兩台Linux機器，有一台串連很快，另外一台輸入密碼後要等好幾秒鐘才能連上。

解決辦法：

在MySQL伺服器的配置中增加一個如下配置後速度飛快。

[mysqld]
skip-name-resolve

附錄：( 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