mysql之skip-name-resolve解决外网链接客户端过慢问题

最新推荐文章于 2021-01-27 02:12:31 发布

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本文介绍了当在腾讯云上部署MySQL并通过Navicat访问时遇到的连接速度慢的问题及解决方案。通过禁用DNS解析和调整相关配置可以有效提高连接速度。

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在腾讯云上面搭建的mysql使用开发的电脑上navicat进行访问时总是特别的慢，原来是Mysql会对请求的地址进行域名解析，开发的电脑并没有域名，所以会导致特别的慢，使用以下进行解决

[mysqld]
skip-name-resolve
skip-grant-tables

官方的解释

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.

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。