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From Paul Querna <>
Subject Re: stress testing of Apache server
Date Tue, 03 May 2005 20:51:55 GMT
Sergey Ten wrote:
> Hello all,
> SourceLabs is developing a set of tests (and appropriate workload data) to
> perform stress testing of an Apache server using requests for static HTML
> pages only. We are interested in getting feedback on our plans from the
> Apache server community, which has a lot of experience in developing,
> testing and using the Apache server.
> Information available on the Internet, as well as our own experiments, make
> it clear that stressing a web server with requests for static HTML pages
> requires special care to avoid situations when either network bandwidth or
> disk IO become a limiting factor. Thus simply increasing the number of
> clients (http requests sent) alone is not the appropriate way to stress the
> server. We think that use of a special workload data (including httpd.conf
> and .htaccess files) will help to execute more code, and as a result, better
> stress the server.

Which tools are you planning to use?  Flood might be useful:

I am not 100% sure on the purpose of your test.  If you want to tune
apache for the highest performance, one of the first things is to remove
.htaccess files.  Doing hundreds of mod_rewrite rules inside an
.htaccess file for example has a *huge* penalty.

> We anticipate that our tests will cover 80% of code (using test and code
> coverage metrics) for the following Apache modules (as most commonly used):
> .	mod_rewrite;
> .	mod_auth and mod_auth_ldap;
> .	mod_ssl.

Which mod_auth? File? DBM? Basic? Digest?

Different MPMs?  Worker, Event, Prefork, Leader.. etc.

It would be nice if you could do 1.3, 2.0 and 2.1.  Some things also
depend greatly on the OS... For the threaded MPMs on linux, using 2.6
and NPTL can make a huge difference.

> We would like to know your opinions and feedback on:
> .	What are the stress scenarios where you have had problems?

Running out of RAM. If the machine runs out of RAM, performance will
tank.  The reason many 'benchmarks' aren't realistic is that they do not
simulate real 'Internet' load.  On the Internet you have a huge range of
clients, from 28.8 modems with 1 full second of latency, to DSL and
everything in between.  Many of the benchmarks are done over 100mbit or
greater LANs, that do not accurately simulate how traffic hits a real

> .	What are the modules (including external) you have stressed which
> are missed from our list?
> .	What are the modules (including external) you would be interested in
> stressing?

In 2.x:

It would also be interesting compare proxying for Tomcat, and test
mod_proxy_ajp vs mod_jk vs mod_proxy_http.

The effects of mod_defalte? (Gzip content compression... look at how
much server CPU for how much less bandwidth it uses?  Most servers of
static content are bandwidth limited, not CPU, so in most cases it makes
sense to use mod_deflate.)

> Additional feedback on the validity of our test plan, ranking modules
> according to their importance, etc would also be much appreciated.

It would be cool to have more details on how you intend to do the
benchmark, including the configuration files, and what client application...

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