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High CPU usage and outbound traffic
https://forum.linode.com/viewtopic.php?f=19&t=6900
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Author:  agentile [ Fri Apr 01, 2011 1:16 pm ]
Post subject:  High CPU usage and outbound traffic

I have recently experienced high cpu + high outbound traffic (both at the same time) spikes. The process causing the high cpu usage is apache. I started looking through apache logs to see if I could spot anything weird. I didn't notice anything in particular.

Any thoughts to what might be causing this? Possible DOS? Someone simply using a download accelerator app? Is it possible for me to limit the outbound traffic/cpu usage per apache thread? I'm not much of an SA but would like some tips as to how I might be to figure out the root cause of these high cpu and outbound traffic spikes.

I have been using tools like htop, iptraf, tcpdump, etc. I guess I'm just hoping for some assistance from people who may have experienced similar issues and how they went about diagnostics and prevention. Thank you.

Author:  Guspaz [ Fri Apr 01, 2011 2:19 pm ]
Post subject: 

You haven't really provided any details... How much CPU usage? How much traffic? Do your apache logs show particular scripts being accessed at the time of the spikes? etc.

Author:  agentile [ Fri Apr 01, 2011 3:02 pm ]
Post subject: 

when the spike happens it is usually hovering at 200%, but in one case it went up to 325% . The outbound traffic goes up to about 35Mbits/sec , the time that cpu usage went to 325% outbound traffic went up to 45Mbits/sec . My normal conditions are very low, cpu usage usually in the 0-1% and outbound traffic usually on the lower end of < 1Mbit/sec

I run quite a few vhosts from this machine, and there is quite a bit of log data (each vhost has its own log files). So I admit I'm having some difficulty determining a good way to sift through the legit requests vs something that may be the offending culprit.

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