Strange CPU / processes behaviour

[NYCreate]

Hi all...
Im very inexperienced with plesk and linux but Ive started to get some really strange behaviour happening at the same time every other day, and I havent got a clue how to diagnose or locate the problem.. can someone please point me in the right direction because this is killing the server every time it happens..

couple of CPU graphs attached to highlight the prob.

Ive looked in apache and nginx error logs but nothing obvious.

Thanks.

 

[abdi]

It's best to run top to know exactly what is happening ..

top

You may also Investigate the cause of high CPU usage on Apache or Nginx ..

Try by:

Getting Connections on Port80

netstat -tulpn| grep :80

netstat -lnp | grep ':80'

No. of Active Connections

netstat -n | grep :80 |wc -l

List ALL IPs in active connections with the number of connections

netstat -apn|grep :80 |awk '{print $5}'|sort

Optimization of Apache

vi /etc/httpd/conf/httpd.conf

For the best performance on most websites leave,

KeepAlive On
KeepAliveTimeout to 1 or 2 seconds

If in the above you are dos-attacked, then you can block the IPs dosing you in your firewall. And if you have CSF already running, then just enable

SYNFLOOD = "1"

 

[NYCreate]

Hi Thanks for this..

Using top during the unusual event and during normal running doesnt show anything thats different, ie all processes are round about the same. Top does not seem to show the same as the graph?

Cpu(s): 0.0%us, 0.0%sy, 0.0%ni, 97.9%id, 0.0%wa, 1.5%hi, 0.5%si, 0.0%st
where as the graph would show a much lower % idle etc

Number of active connections at this time is 4 from 2 IPS

I check the IPs and both seem like normal traffic.
I also get loads of server emails saying services are down and restarted etc.

Im still stumped as to whats doing this, but its affection my clients now as they have noticed their sites are almost unusable during one of these events for up to 4 hours at a time. not good :-(

Any other suggestions please?
Todays CPU event attached.

Thanks in advance

 

[NYCreate]

Friendly BUMP ^^ still causing me severe issues every day now :-( also blocked processes seem to jump big time when this is happening? not a clue whats going on.

Thanks in advance