Why Does My MySQL Connection Fail with Error 2006 ('MySQL Server Has Gone Away') and How Can I Fix It?

Understanding and Resolving MySQL Error 2006: "MySQL Server Has Gone Away"

When running a server that processes files and reports the results to a remote MySQL server, users may encounter the error "2006, MySQL server has gone away." This indicates that the connection to the server has been unexpectedly terminated prematurely.

Contrary to common assumptions, the issue is not typically related to the wait_timeout setting. Instead, the solution lies in another MySQL parameter: max_allowed_packet.

max_allowed_packet: The Key to Resolution

The default max_allowed_packet setting, often found to be as low as 4MB (4194304 bytes), can be inadequate for processing large data packets. When the data payload exceeds this limit, the server disconnects, causing the "MySQL server has gone away" error.

To resolve this, increase the max_allowed_packet value in the [mysqld] section of the /etc/my.cnf configuration file on your server. A setting of 8 or 16MB is typically sufficient.

For example:

[mysqld]
...
max_allowed_packet=16M
...

Alternatively, you can use the following command to set the parameter dynamically (changes will be lost upon restart):

SET GLOBAL max_allowed_packet=104857600;

Additional Notes:

• Ensure the my.cnf file is saved with ANSI encoding (not UTF-8) on Windows systems.
• On Windows, the my.ini file may need to be edited instead.
• If the error persists after adjusting max_allowed_packet, consider checking other MySQL parameters such as read_timeout and wait_timeout.

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