Issue Scheduled task cause all websites to be unavailable for a few minutes

[orenk]

Server operating system version

CloudLinux 8

Plesk version and microupdate number

Plesk 18.0.73 #03

Hi.
There is probably a scheduled task, which I can't find, that cause all the wordpress websites to be unavailable around 5 minutes. (timeout or very slow response)
this happens every day between 4:00am and 4:30am (different time every day, but around this window time).
at that time, PLESK panel is very slow. the RAM and NETWORK shows normal levels, the CPU is around 20%-30% (the average is 15%-20% at noon time)

When I SSH to the server, and use "TOP" to see the active processes, I can see the PHP-FPM and LSPHP (cloud linux) are very high at this time. like 30% each

since it happens at the same time frame every day, I suppose it is a scheduled task. but I can't find which task it is.
but I can't find any task that starts around 3:30am-4:30am (except the clean-sysstats)
I looked for it in the following:
1. Plesk GUI, Scheduled Tasks
2. root # crontab -l
3. scheduled backup (which I moved to 14:00)

any other ideas where I can search scheduled tasks ?
plesk 18.0.73 + cloudlinux 8 (but it happens for a few months now, so the plesk version is less relevant

Thanks

 

[Raul A.]

Hi,

Cron task execution is logged in /var/log/cron. You will find there all the tasks that were executed.

How do you back up your data? Is it scheduled within this timeframe?

 

[Bitpalast]

It might not be caused by a real cron, but by one specific website. For example it could be a backup plugin of a specific website that is triggered by the Wordpress internal cron (which won't show up in the cron logs). To find out what the top transactions really are, run

MYSQL_PWD=`cat /etc/psa/.psa.shadow` watch "uptime && echo "\ " && ps aux | sort -nrk 3,3 | head -n 20 && echo "\ " && mysqladmin proc status -u admin"

and observe which website requests the CPU attention when the CPU load strongly increases.

 

[orenk]

Hi,

Cron task execution is logged in /var/log/cron. You will find there all the tasks that were executed.

How do you back up your data? Is it scheduled within this timeframe?

Thanks.
I viewed the file you mentioned, I have found countless CRONTAB, about 5-8 executing each minute. (I checked from 3:50 to 4:10)
so its kind of very hard to identify which cron tab causing it, unless I will execute each one of them... which I might do...
I have found many crons related to the "imunify" , and even though it is set to scan all the websites weekly on Sunday at 4am, maybe it runs daily...
So I tried to set it to run on a different hour, and I'll see if something change.

regard your question about the backup, I moved the backup time (from PLESK GUI) to noon time, and it did not solve the problem, so I suppose it is not related to the Plesk backup.
I also have an external image backup, which backs up the entire VPS drive, but that happens around 2am, and it backs up a shadow copy, so it should not affect the VM performance.

Thanks.

 

[orenk]

It might not be caused by a real cron, but by one specific website. For example it could be a backup plugin of a specific website that is triggered by the Wordpress internal cron (which won't show up in the cron logs). To find out what the top transactions really are, run

MYSQL_PWD=`cat /etc/psa/.psa.shadow` watch "uptime && echo "\ " && ps aux | sort -nrk 3,3 | head -n 20 && echo "\ " && mysqladmin proc status -u admin"

and observe which website requests the CPU attention when the CPU load strongly increases.

I will look into that, but thats exactly why I am using Cloud Linux, because of the DB Governor.
It happened to me previously, that single wordpress overloaded the DB, and since then I decided to move to cloudlinux.
I hope this is not the case right now.. but I will check it anyway. maybe I will find other clues..