MySQL報錯Can not connect to MySQL server. Too many connections，報錯很明確，與MySQL的連接數(shù)滿了。mysql最大連接數(shù)默認(rèn)為100，看來有必要改大一點了。

方法:修改配置，然后重啟

vi /etc/m.cnf加入max_connections=1024，然后重啟mysql即可。

需要注意的是有時候重啟后max_connections變成了214，這就很詭異了。
查閱了官方文檔:

The maximum number of connections MySQL can support depends on the quality of the thread library on a given platform, the amount of RAM available, how much RAM is used for each connection, the workload from each connection, and the desired response time. Increasing open-files-limit may be necessary. Also see Section 2.5, “Installing MySQL on Linux”, for how to raise the operating system limit on how many handles can be used by MySQL.

把上述語句概括起來就是，max_connections依托于操作系統(tǒng)，Linux系統(tǒng)必要時需要增加open-files-limit。萬萬沒想到啊，修改max_connections竟然要修改操作系統(tǒng)最大文件描述符。

vi /usr/lib/systemd/system/mysqld.service加入

LimitNOFILE=50000

重啟MySQL