Fixing the MySQL Error 1040: Too many connections

Fixing the MySQL Error 1040: Too many connections

When working with MySQL servers, you may face errors from time to time. One of them is the MySQL Error 1040: Too Many Connections. So what does this error message means? And how to deal with it? The message basically means that the server has reached maximum number of alloted connections. So it can’t handle more connection requests. As a consequence, some or all of the connections will get affected. In worse situation, the entire website will be down for some time. In this article, learn how to fix this error.

Here are a few things you need to know before starting the troubleshoot process:

You’d need a threat handling mechanism of a third-party (usually of the operating system) since MySQL doesn’t have a threat handling mechanism of its own.

There’s a system variable in MySQL called “max_connections.” It controls the number of connections the server can handle at one time. If the number of connections exceed that mentioned in the variable, you’ll get the Error 1040.

How connection handling works in MySQL?

In this section, learn how MySQL handles the connection to the server. First an MySQL client connects to the server via the TCP-IP connect message. It sends out a connection request through port 3306 on Server instance. These requests, coming from one or multiple clients, are queued by receiver thread. The receiver threat creates user thread and then processes the requests one by one. In here, the user threat is responsible for handling the client-server protocol. For that, it allocates and initializes the relevant THD that correspond to the credentials stored in THD’s security directories. This is important for security purposes. Once verified in the connection phase, that threat will enter command phase.

Based on the availability, the receiver thread will use an existing OS thread in the thread cache or create a new OS thread. When the number of connections probability is high, we recommend to increase the thread cache size.

If you don’t know what THD is, then it’s a large data structure that’s used for authorization and connection management. It’s a handy tool that’s also be used for query execution if needed. THD will also consume resources but depends on the complexity of the operation and incoming traffic.

How to Fix the MySQL Error 1040?

From time to time, especially when your website faces high traffic, you’re going to get the “Error 1040: Too many connections” message. The message clearly demonstrates what has gone wrong. Your website is simply receiving too many connection requests and the server is failing to cope up with the demand.

To fix the error, we have to first tweak the max_connection system variable. So identity the max_connection variable with the following command:

mysql --user="root" --password="PASSWORD" --execute='SHOW VARIABLES LIKE "max_connections";
The output will be a table with the parameter max_connections that’s set a number. You need to increase this number.

Now, open the my.cnf file that can be found at /etc/mysql/my.cnf. Looking for the following parameters and change their value:

max_connections = 500
max_user_connections = 500
Restart the MySQL service. This should apply the changes you’ve made to the my.cnf file.
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