Getting 'Communications link failure' CommunicationsException Error when Making XML Backup
Platform Notice: Data Center - This article applies to Atlassian products on the Data Center platform.
Note that this knowledge base article was created for the Data Center version of the product. Data Center knowledge base articles for non-Data Center-specific features may also work for Server versions of the product, however they have not been tested. Support for Server* products ended on February 15th 2024. If you are running a Server product, you can visit the Atlassian Server end of support announcement to review your migration options.
*Except Fisheye and Crucible
Symptoms
Using MySQL, when making a manual XML backup, the database connection is timing out. The following appears in the atlassian-confluence.log:
com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception
Cause
According to the MySQL manual:
The number of seconds the server waits for activity on a non-interactive connection before closing it. This timeout applies only to TCP/IP and Unix socket file connections, not to connections made via named pipes, or shared memory.
On thread startup, the session wait_timeout value is initialized from the global wait_timeout value or from the global interactive_timeout value, depending on the type of client (as defined by the CLIENT_INTERACTIVE connect option to mysql_real_connect()). See also interactive_timeout.
Resolution
This problem is resolved by adjusting the wait_timeout parameter to a higher value.
If problems persist after making the changes, switch to a different Production Backup Strategy.