Weird apache status values with nginx

[Maxim Dounin]

Hello!

On Tue, Jul 17, 2012 at 01:28:22PM -0400, migue76 wrote:

> Hello.
> 
> Since I have installed nginx on our dedicated server I'm having some odd
> issue. The "cpu usage" and "requests currently being processed" are not
> correct on apache-status
> 
> A couple of image to see ir clearly. Images from same server at same
> time, same accounts and similar traffic:
> 
> http://i46.tinypic.com/nbte09.jpg <--- good
> 
> http://i46.tinypic.com/1jsot5.png <--- bad
> 
> Please, look at "cpu usage": u601?? s261?? cu4368?? However, cpu load is
> correct

Why do you think it isn't correct?  Two days at 3% cpu usage is 
something about 5000 cpu seconds.

Keeping in mind that in Apache server status's "CPU load" is just 
(u + s + cu + cs ) / uptime, it's highly unlikely that cpu usage 
stats would be incorrect while cpu load reported is correct.

The fact that Apache's cpu usage is different from what you have 
without nginx might have many reasons.  Possible ones are ranging 
from incorrect Apache configuration which causes neeedless process 
startup/shutdown (which now happens more often due to low worker 
process utilization) to just a simple fact that your system 
handles more requests now (and consumes more CPU as a result) due 
to no longer being limited by some other resource.

> Look at "requests currently being processed": 4 request only? More than
> 300 websites at high traffic time and only 4 request? How is it
> possible?

This is normal, as working with slow clients is offloaded to nginx 
now.  Apache processes are no longer busy waiting for a client 
to sent rest of a request or read another part of a response.

[...]

Maxim Dunin