MySQL Too many connections
Recently, I saw some blank pages on my website without any error, especially when the web server was very busy. I suspected that somewhere in PHP codes caught the exception and threw nothing. So I decided to display the error on the screen and saw MySQL too many connections error like this:
It looked like a resource limitation on connections was over, so I first checked the current value of max_connections, which is the limitation on how many connections is allowed to use.
mysql> show variables like 'max_connections';
| Variable_name | Value |
| max_connections | 151 |
1 row in set (0.00 sec)
It's the default value. So I decided to lift the connection limit of mysqld like this:
[root@test ~]# vi /etc/my.cnf
After that, you should restart mysqld to make max_connections take effect.
[root@test ~]# systemctl restart mysqld
Please periodically check how many connections that is created during the busy hours of server. Furthermore, you may need to raise innodb_buffer_pool_size to meet the new value of max_connections.
mysql> show processlist;
Then you will know how many connections that MySQL really needs, that's how we prevent MySQL Too many connections.