Starting yesterday (May 27, 2025) the forum began having problems, showing "An error occurred while the page was being generated".
After some investigation, the problem turned out to be a "xf_session_activity" table grew too large. Apparently it's a common problem on some other Xenforo-based forums.
For a quick fix, I changed the mysql config files to allow up to 64MB in memory tables. Apparently the default was 16MB. Hopefully this will be enough to keep the problem from happening again.
Another suggestion I didn't do (yet) was a script that checks for the problem and truncates the xf_session_activity table.
Mentioned on 1 of those other Xenforo threads linked from msg #2 was some discussion about the likely root cause... spiders or spammers hitting the server really hard with lots of page requests, which apparently can fill up that memory-based session table. If this problem keeps coming back even with the table allowed to grow 4X larger, then I'll start to look at ways we might detect and throttle or block badly behaving bots.
At least right now we've back up and running, with only the max table size setting increased. I'm not eager to pour a lot more work into this problem until it's really more of a problem. But I did want to take some time to explain what went wrong (also for future me when/if more work is needed) since the on-screen "An error occurred..." message gave basically no useful info about the actual problem.
After some investigation, the problem turned out to be a "xf_session_activity" table grew too large. Apparently it's a common problem on some other Xenforo-based forums.
For a quick fix, I changed the mysql config files to allow up to 64MB in memory tables. Apparently the default was 16MB. Hopefully this will be enough to keep the problem from happening again.
Another suggestion I didn't do (yet) was a script that checks for the problem and truncates the xf_session_activity table.
Mentioned on 1 of those other Xenforo threads linked from msg #2 was some discussion about the likely root cause... spiders or spammers hitting the server really hard with lots of page requests, which apparently can fill up that memory-based session table. If this problem keeps coming back even with the table allowed to grow 4X larger, then I'll start to look at ways we might detect and throttle or block badly behaving bots.
At least right now we've back up and running, with only the max table size setting increased. I'm not eager to pour a lot more work into this problem until it's really more of a problem. But I did want to take some time to explain what went wrong (also for future me when/if more work is needed) since the on-screen "An error occurred..." message gave basically no useful info about the actual problem.