Normally, the parameter max_connections in MySQL is set to 151 and allowed for one connection more, that is, there may be 152 connections.
If there are more connections, there will be a “too many connections” error.
On an example I use MySQL 5.5.54.
To increase the value, we connect to MySQL:
mysql -u root -p
Let’s see a list of current connections:
show processlist; SHOW FULL PROCESSLIST\G show status where `variable_name` = 'Threads_connected';
Let’s see the current value of max_connections:
show variables like "max_connections";
If you need to increase it without restarting MySQL (it will work before restarting MySQL):
set global max_connections = 300;
So that after the restart of MySQL the value of max_connections is preserved, in the configuration file /etc/mysql/my.cnf, in the [mysqld] section we specify it:
max_connections = 300