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From Jason Cillo <jasonci...@comcast.net>
Subject Re: [users@httpd] High CPU Usage in Amazon EC2
Date Thu, 03 Apr 2014 15:35:17 GMT
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Have you looked at OpenSSL Cookbook? It's free. I find it very useful. (I even bought the
larger book of which it is a chapter.)

...Jason


On Apr 3, 2014, at 10:23 AM, Christopher Schultz wrote:

> All,
> 
> I forgot to mention that most of our traffic is over SSL. OpenSSL
> version is OpenSSL 1.0.1e-fips 11 Feb 2013.
> 
> Thanks,
> -chris
> 
> On 4/3/14, 10:04 AM, Christopher Schultz 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.
>> 
>> 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.
>> 
>> It seems to come in waves: the load will go up, and everything will slow
>> down, and then we'll get a reprieve.
>> 
>> 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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