I had an issue today with a gallery upgrade in that I upgraded the gallery to 2.3.1 version as per the documentation. However, the galleries (there were about 14k images in about 9GB) displayed ok, while a couple of them had broken thumbnail placeholders. Gallery’s logs were no help and neither were apache’s logs.

I tried to use the maintenance section of the site admin to regenerate all thumbnails and derivatives, but got various errors including ERROR_STORAGE_FAILURE and ERROR_LOCK_FAILURE among a few others. I was also getting quite a lot of mysql server has gone away errors which probabaly were due to mysql query restrictions on the server to prevent abuse.

After a lot of googling and running through the faqs and troubleshooting sections of menalto’s gallery site, finally figured out a set of actions that seemed to temporarily fix the issue.
1. Go to http://site/lib/support, enter the setup password, and click on cache maintenance. Leave the logs and the thumbnails unchecked and run it.
2. In http://site/main.php after login, go to Site Admin>Maintenance>Delete Template Cache. If this gives some errors, it seemed ok to ignore it.
3. Open the database via phpmyadmin and run find the max value of g_id in g2_Entity. Increment the value by 1 and insert that value to the row in g2_Sequenceid (There should be only one row and if the value of the query ‘select max(g_id) from g2_Entity’ is 34523, the row in g2_Sequenceid should be 34524)

Now rerun the generate all thumbnails and derivatives from Site Admin>Maintenance

I still have issues running it as the memory limit seems to setup at 32mb. Working on fixing that.