Recently we had a phase of high wiki usage - >100 users were accessing the wiki in a short time frame. What the users did was mainly commenting on existing pages.
At some point comments were no more saved into the database - the users sent the comment and got the green “Comment saved” but after refreshing the page the comment was not displayed. This happened to all documents from that time on, no commenting was possible (except for a few exceptions which I still don’t understand).
Analyzing this I found a related error which was that editing objects was not possible for pages with comments - a 4001 was thrown in editobject.vm. (Comments are technically also objects as I understand it.) For pages without comments, editing objects still worked. For the above error, the log gave a IndexOutOfBounds error description.
Having direct database access, I could nail down the cause to a missing timestamp in table xwikidates for an xws_id related to a comment property - the entry in xws_value was NULL. I directly updated this value with a meaningful timestamp and all the above errors were resolved.
That is, I do not have an urgent requirement for help. However, this issue obviously caused some stability concerns in me - this must not happen again for us, otherwise thy buy-in for the wiki will be seriously at stake. My questions:
- How can such a thing happen?
- Has anyone experienced something similar?
- Might it be a thing specifically related to comments?
- Do we need to prevent highly concurrent editing usage of the wiki at all?
- Giving the green “comment saved” when it is actually NOT saved is an issue in itself. Can this false positive be prevented?
Thanks for any pointers. Happy to provide more details if needed. We are using 13.10 with PostgreSQL and Tomcat behind a Nginx proxy and a Kubernetes deployment. Over all, XWiki is a great application and we’re grateful having it installed.