The following error appear in the Plesk interface:
PLESK_INFO: Unable to connect to database: Too many connections
SQLSTATE  Too many connections
This error means that the maximum number of simultaneous connections to the MySQL server has been reached. New connections to the server cannot be established at this time.
- Connect to the server using SSH.
Check the number of current connections to the server, use:
# mysqladmin -uadmin -p`cat /etc/psa/.psa.shadow` extended-status | grep Max_used_connections
| Max_used_connections | 11 |
The current connection limit can be found using:
# mysqladmin -uadmin -p`cat /etc/psa/.psa.shadow ` variables | grep 'max.*connections'
| max_connections | 100 |
| max_user_connections | 0 |
In the above example, the maximum number of connections to the server (For RHEL-based systems:
max_connections) is set to 100. The maximum number of connections per user (
max_user_connections) is zero, which means unlimited. The default MySQL values can be redefined i, the file
For Debian-based systems:
Restart MySQL after
my.cnfhas been modified:
# service mysqld restart
Warning: if you set the connection limit to a very high value (more than 300), this may affect server performance. It is better to find and rectify the cause of the high MySQL server usage.
You can check which users/requests slow MySQL on all current connections with the following command:
# mysqladmin -uadmin -p`cat /etc/psa/.psa.shadow` processlist