Knowledge Base

Plesk and/or websites are inaccessible: SQLSTATE[08004] [1040] Too many connections error

Symptoms

The following error message appears in the Plesk interface or during Plesk migration process:

Unable to connect to database: Too many connections
SQLSTATE[08004] [1040] Too many connections

ODBC error #HY000: [unixODBC][ma-3.0.8]Too many connections
Websites fail to load with the error:

Error Establishing a Database Connection
Plesk license installation fails with the error:

Incorrect ServerInfo format (Error code: 2)

exit status 1

Cause

The maximum number of simultaneous connections to the MySQL databases has been reached and new connections to the server cannot be established.

Resolution

For Plesk on Linux

Note: On Linux server with MySQL installed, the max_connections limit cannot be higher than 214, unless the solution from this KB article is applied.

# Automatic Solution

Connect to the Plesk server via SSH.
Download the script that will set the MySQL parameter max_connections to 300:

# wget https://raw.githubusercontent.com/plesk/kb-scripts/master/mysql-max-connections/mysql-max-connections.sh
Make the script executable:

# chmod +x mysql-max-connections.sh
Execute the script:

# ./mysql-max-connections.sh

Note: If the automatic solution did not help, apply the manual solution below.

# Manual Solution

Connect to the Plesk server via SSH.
Find the current max_connections value:

# plesk db "SHOW VARIABLES LIKE 'max_connections'"
+-----------------+-------+
| Variable_name | Value |
+-----------------+-------+
| max_connections | 151 |
+-----------------+-------+
Open the MySQL configuration file my.cnf in a text editor. In this example, we are using the vi editor:
- on CentOS/RHEL-based distributions
  
  # vi /etc/my.cnf
- on Debian/Ubuntu-based distributions
  
  # vi /etc/mysql/my.cnf
Increase the number of connections by adding this directive under the [MySQLD] section:

[mysqld]
max_connections=300
Save the changes and close the file.
Restart MySQL/MariaDB service to apply the changes using one of these commands:

# service mysql restart

# service mariadb restart

For Plesk on Windows Server

Connect to the Plesk server via RDP.
Open the MySQL configuration file %plesk_dir%DatabasesMySQLmy.ini in a text editor.
Increase the number of connections by adding this directive under the [MySQLD] section (the default value is 300):

[MySQLD]
max_connections=300
Save the changes and close the file.
Restart the MySQL/MariaDB service Plesk Management Service using Windows Plesk Services Monitor