mysql连接数 2023-02-17
2023-02-16 本文已影响0人
9_SooHyun
在使用 MySQL 的时候，可能会遇到一个问题，“Can not connect to MySQL server. Too many connections” -mysql 1040 错误，这是因为MySQL还未释放的连接数已经达到设置的上限，无法建立新连接
MySQL无论如何都会保留一个用于管理员（SUPER）登陆的连接，用于管理员连接数据库进行维护操作，即使当前连接数已经达到了max_connections。因此MySQL的实际最大可连接数为max_connections+1
查看最大连接数相关参数
show variables like '%max_connections%'; --mysql设置的最大连接数
show global status like 'Max_used_connections'; --The maximum number of connections that have been in use simultaneously since the server started.
show global status like 'Max_used_connections_time'; --The time at which Max_used_connections reached its current value.
查看当前连接的状态
mysql> show global status like 'Threads%';
+-------------------+-------+
| Variable_name | Value |
+-------------------+-------+
| Threads_cached | 49 | The number of threads in the thread cache.
| Threads_connected | 2 | The number of currently open connections.
| Threads_created | 201 | The number of threads created to handle connections. If Threads_created is big, you may want to increase the thread_cache_size value. The cache miss rate can be calculated as Threads_created/Connections.
| Threads_running | 2 | The number of threads that are not sleeping.
Threads_cached ## mysql管理的线程池中还有多少可以被复用的资源
Threads_connected ## 打开的连接数
Threads_created ## 表示创建过的线程数，如果发现Threads_created值过大的话，表明MySQL服务器一直在创建线程，这也是比较耗资源，可以适当增加配置文件中thread_cache_size值，查询服务器
