Symptoms

When restoring a Confluence site or space XML backup, the progress bar eventually stops advancing and stays that way indefinitely.

No errors appear on screen or in the logs. The  atlassian-confluence.log indicates that the import has been started, but nothing follows:

2012-06-10 16:38:10,273 INFO [Long running task: Importing data] [confluence.importexport.actions.ImportLongRunningTask] runInternal Beginning import by user admin

Cause

MySQL's packet size setting may be set too low. 

Resolution

Set the MySQL packet size to 32M or larger and restart MySQL Server.

For MySQL versions 4.0 and later, use this syntax:

shell> mysqld --max_allowed_packet=32M

Alternatively, you can do this on your MySQL server's settings by editing MySQL's my.cnf file (often named my.ini on Windows operating systems). Locate the [mysqld]section in the file, and add/modify the following parameters:

[mysqld]
...
max_allowed_packet = 32M
...

For more information, please refer to MySQL manual: http://dev.mysql.com/doc/refman/5.0/en/packet-too-large.html.