Mysql: increase the maximum number of connections

occasionally , In connection MySQL Database time , The connection will fail , And back to  "too many connections"  Error message . This is due to the current MySQL Too many connections for , The maximum number of connections allowed has been exceeded .

here , You can try connecting more times MySQL Database or wait a while before connecting . If you have been unable to connect to the database , You need to restart MySQL 了 .

If you try several times , Can be connected to MySQL Database , You can view the current number of connections through the following command ：

SHOW STATUS WHERE `variable_name` = 'Threads_connected';

  And pass  SHOW PROCESSLIST [1] Command to view connection details ：

SHOW PROCESSLIST

confirm MySQL A large number of connections is a normal connection requirement , Not because of the program bug As a result of , You can improve MySQL Maximum connections limit .

MySQL The default maximum number of connections is 151, You can view it through the following statement ：

SHOW VARIABLES LIKE '%max_connections%';

take MySQL The maximum number of connections increased to 300：

SET GLOBAL max_connections = 300;

Through modification MySQL Variable to modify MySQL Configuration mode , Can be restarted without MySQL In the case of service , To give immediate effect to a modification . But the downside is , stay MySQL After the service is restarted , Your changes will be invalidated .

In order to make our modification lasting , Need modification MySQL Configuration file for . basis MySQL It's installed in different ways , as well as Linux The difference in distribution , The location of the configuration file you need to modify will also be different , For details, please refer to your Linux Distribution documentation and documentation of the installation method you use .

stay Ubuntu 18.04 in , adopt APT Installed MySQL, The configuration file that needs to be modified is  /etc/mysql/mysql.conf.d/mysqld.cnf, stay  [mysqld]  below , Add the following configuration statement ：

max_connections = 300

Save file and exit .

In this way MySQL After restart , The changes we made will still be valid .

Reference resources ：

[1]: https://www.mysqltutorial.org/mysql-show-processlist/

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