We recently upgraded from Moodle 3.6 to 3.11.18 (Yes I know, we're behind, but we're in the process of catching up. As of right now, upgrading to 4.0+ is not feasible yet). We are using Moodle's backup and restore functionality to copy courses, but after upgrading, some of our courses fail to copy. The backups complete just fine, but during the restoring of a backup, it simply stops without error.
We are using a custom plugin that is not much more than a wrapper for creating a backup and restore. The backup/restore code from Moodle itself is untouched. This is triggered through a cron, but after the restore fails, it fails in such a fashion that the task log is not even available in the UI. Our custom plugin does not silently swallow any exceptions.
What we have done so far:
- Investigated the difference between courses copies that do succeed and those that don't
- This unfortunately hasn't resulted in much information yet
- Added logging to Moodle's restore to find out at which step it fails
- We found out that it consistently fails during the decode_interlinks step
- Adding more logging, it seems to stop somewhere after starting the step that runs for the question_answers table.
- Ruled out that system timeouts or memory limits are the issue
When we do not include the question bank within our backup/restore, it is quick and completes without issue. We are thinking it may have something to do with improperly formatted questions or categories, but after having done a lot of Google searches, as well as on this forum, so far we've not found any solution to this problem.
It would be helpful if anyone had any suggestions for directions we should look into.
Thank you!