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From Christopher Schultz <>
Subject Re: [users@httpd] High CPU Usage in Amazon EC2
Date Thu, 03 Apr 2014 14:38:42 GMT

On 4/3/14, 10:33 AM, Oscar Knorn wrote:
> Sounds like apache is waiting for a response or a means to forward the
> request via stunnel.
> Is /dev/random or /dev/urandom providing sufficient random to the process?

I'm not sure how to check that. Any ideas?

In either case above, wouldn't the processes be sitting idle waiting for
blocking IO to return? I'm not surprised that the bytes are moving
slowly, actually. I'm surprised that I'm pegging my CPU waiting for
bytes to move...


> On 4/3/14, 40:23 PM, 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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