This issue occurs mostly when the maximum allowed concurrent connections to MySQL has exceeded. The max connections allowed is stored in the global variable max_connections. You can check it by show global variables like max_connections; in MySQL

You can fix it by the following steps:

Step1:

Login to MySQL and run this command: SET GLOBAL max_connections = 100;

Now login to MySQL, the too many connection error fixed. This method does not require server restart.

Step2:

Using the above step1 you can resolve ths issue but max_connections will roll back to its default value when mysql is restarted.

In order to make the max_connection value permanent, update the my.cnf file.

Stop the MySQL server: Service mysql stop

Edit the configuration file my.cnf: vi /etc/mysql/my.cnf

Find the variable max_connections under mysqld section.

[mysql]
max_connections = 300

Set into higher value and save the file.

Start the server: Service mysql start

Note: Before increasing the max_connections variable value, make sure that, the server has adequate memory for new requests and connections.

MySQL pre-allocate memory for each connections and de-allocate only when the connection get closed. When new connections are querying, system should have enough resources such memory, network and computation power to satisfy the user requests.