too many connections是由于mysql配置中连接数过少，不足以支撑当前的并发数，too many open files是由于mysql open_files_limit的值大小不够。
最开始mysql日志出现的错误为too many connections，mysql配置文件已经配置了最大连接数max_connections=2000，登录到mysql中，查看mysql连接收:show processlist; (查看详细执行信息使用：show full processlist;)，发现线程数只有500多，并没有达到配置文件中的最大配置，登录mysql查看其生效的最大连接数及mysql open_files_limit
mysql> show variables like '%max_connections%'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_connections | 214 | +-----------------+-------+ 1 row in set (0.00 sec) mysql> show variables like '%open_files_limit%'; +------------------+-------+ | Variable_name | Value | +------------------+-------+ | open_files_limit | 1024 | +------------------+-------+ 1 row in set (0.00 sec)
配置文件中配置的连接数2000未生效
linux一切皆文件，查看linux open files
[root@localhost work]# ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 7739 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) 7739 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited
open files的大小只有1024，需要调大一些，设置为65535
vim /etc/security/limits.conf
添加
* soft nofile 65535 * hard nofile 65535
重新打开ssh窗口，登录,查看设置结果
[root@localhost ~]# ulimit -n 65535
使mysql配置生效有如下两种方式
1、登录mysql，查看连接数，没有变化，还是214，在mysql开机启动服务文件中添加如下
vim /usr/lib/systemd/system/mysql.service
LimitNOFILE=infinity
LimitMEMLOCK=infinity
重启mysql
systemctl daemon-reload
systemctl restart mysql
查看最大连接数连接数及mysql open_files_limit,可以发现open_files_limit的大小被设置为与unlimit -n大小一致
mysql> show variables like '%open_files_limit%'; +------------------+-------+ | Variable_name | Value | +------------------+-------+ | open_files_limit | 65536 | +------------------+-------+ 1 row in set (0.00 sec) mysql> show variables like '%max_connections%'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_connections | 2000 | +-----------------+-------+ 1 row in set (0.00 sec)
2、如果未使用开机启动，使用mysql_safe也可以使配置生效，但open_files_limit的大小被设置为了10000
mysql> show variables like '%open_files_limit%'; +------------------+-------+ | Variable_name | Value | +------------------+-------+ | open_files_limit | 10000 | +------------------+-------+ 1 row in set (0.00 sec) mysql> show variables like '%max_connections%'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_connections | 2000 | +-----------------+-------+ 1 row in set (0.00 sec)
总结：
调大linux系统open files
设置mysql max_connections
1、如果使用开机启动，则在service文件中添加
LimitNOFILE=infinity
LimitMEMLOCK=infinity
使配置生效，并重新启动
systemctl daemon-reload
systemctl restart mysql
2、未使用开机启动，使用mysql_safe启动(open_files_limit被设置为10000，如果不够大，可以在配置文件my.cnf中修改)
mysqld_safe --defaults-file=/etc/my.cnf &