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From Igor Cicimov <icici...@gmail.com>
Subject Re: [users@httpd] High CPU Usage in Amazon EC2
Date Fri, 04 Apr 2014 09:39:27 GMT
On 04/04/2014 1:05 AM, "Christopher Schultz" <chris@christopherschultz.net>
wrote:
>
> All,
>
> I'm having a problem in production I've never seem before. We are
> running a pair of AWS EC2 m1.micro web servers where only one of them in
> really in service at any given time. The httpd instance serves some
> static content and forwards a great deal of traffic via stunnel to a
> single back-end Tomcat server using mod_jk 1.2.37. We have been running
> under this configuration for several years with no problems.
>
Enable the stunnel logs maybe they will reveal something?

> Last weekend, we upgraded our OS to Amazon Linux 2014.03 (32-bit) from
> Amazon's previous version (I can't remember which one), including the
> package-refresh that comes with it for httpd. The current kernel version
> is 3.10.34. The current httpd version is 2.2.26. The package name is
> "httpd-2.2.26-1.1.amzn1.i686" if anyone is interested. We are using a
> prefork MPM with the following (default) settings:
>
> StartServers       8
> MinSpareServers    5
> MaxSpareServers   20
> ServerLimit      256
> MaxClients       256
> MaxRequestsPerChild  4000
>
> What I can observe is that the CPU load average is rising from the usual
> sub-2.0 value to sometimes as high as 70. That's seventy, not
> seven-point-oh.
>
> I see no errors in the log, and httpd doesn't seem to be dropping any
> requests... just running very very slowly.
>
What if you increase the LogLevel to debug? Meaybe jkLogLevel too.

> It seems to come in waves: the load will go up, and everything will slow
> down, and then we'll get a reprieve.
>
Whats the memory usage at those times? If you have sysstat installed you
can run sar for some stats about disk cpu and memory.

> I can see 22 server processes running right this moment, but the load
> average has dropped back to 0.05.
>
> I've enabled ExtendedStatus and it really doesn't look like there is a
> huge number of requests being served. Less than 1 req/sec. This is *not*
> a high-load server. I can see some of the httpd child processes using
> 20% or more of the CPU as reported by 'top'.
>
> Is there a good way for me to determine what those processes are doing?
> As this is a modestly-used server, I can probably enable additional
> logging without too much trouble.
>
> Any help anyone can provide would be very much appreciated.
>
> Thanks,
> -chris
>

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