Website crashed probably due to too many MySQL threads

[Huckleberry]

My website crashed this morning at around the same time as WP-Optimize ran this hook:

Hook Name	Arguments	Actions	Next Run	Recurrence
wpo_smush_clear_backup_images	None	
Updraft_Smush_Manager->clear_backup_images()
2019-12-10 04:06:51 (17 hours 30 minutes)	Once Daily

Have a look at Munin’s MySQL thread statistics which skyrockets just before the website goes down. I then rebooted the server a few hours later as you can see:
https://hmp.me/ct1j

My website has thousands of (small) images, and I wonder if this hook might overload the system.

[Marc Lacroix]

Hi,

I don’t think the spike in MySQL threads is due to this hook, as it only does 1, maybe 2 sql calls in order to get an option.

The rest is all done at a filesystem level.

So if the mysql threads are the cause of the crash, it’s probably not from this part of the code.

Is there anything else in your logs?

Marc

[Huckleberry]

Hi @marcusig,
I’m not the most WP savvy guy… could you point me in the direction of which log to look into?

[Marc Lacroix]

I would look in 2 places:
– the php error log, for eventual fatal errors
– considering the spike in MySQL threads, I would take look at the visits and error logs from your server software (e.g. Apache or Nginx…) to see if there was an attempted attack.

Marc

[Huckleberry]

– error.log showed nothing
– the server log didn’t show anything special
However, I found a great open-source monitoring system that I will use to track for the next time it happens.

Thank you for your guidance.

[Huckleberry]

@marcusig I think it was another plugin that was up to no good. It turned out to be an out-of-memory condition.

Happy New Year, and thanks for a good plugin.

[Marc Lacroix]

Hi, Thanks for the update.
Happy new year to you.

Marc.