Website Load Testing Tools?

bLanark asks: "I'm in the process of converting one of my clients from IIS/CGI to Apache/mod_perl. I need a (free) web site stress/load test tool to prove that performance will be increased. Using this page as my starting point, I can see that there are quite a few tools to investigate. Has anyone used any of these (or any others) and what are they like. I need HTTP GETS, form POSTing, and clever stuff like simulation of caching of images would be useful too, I guess." The previous story didn't get much of a response, but that was about a year ago, but the submittor has shared a fairly impressive list with us, impressions about any piece of software on it would be greatly appreciated.

Comments

Designing the tool

[DeadSea]

I don't know what is out there, but if I were picking a tool, I would make sure that it measures real world cases. This means that you should be able to give it your server log for a week (make sure you log post data and cookies) and the tool would test your server just like it is actually used. It would also be able to test for increased traffic by combining several weeks at a time (Like all the visitors that came on 4 Wednesdays came on one day).

I would also think that it would have to be distributed (at least across several computers) to ensure that bandwidth and cpu/memory of the testing computer are not the limiting factors.

How hard can it be to write something like that? The hardest part would probably be parsing the log files. I would not be suprised if there are several testing tools that would do an adequate job.

Be sure to simulate "real life"

[linuxwrangler]

At least as much as possible.

In a previous job we needed to do some benchmarking and testing. The first pass was to script some stuff using wget. Once everything looked fine (we could really slam the server) we turned it loose on the public.

Oops. The site collapsed nearly instantly. The problem was that people with slow modem connections kept connections active for a couple orders of magnitude longer than happened on our internal network and the server ran out of resources.

Microsoft's free tool can simulate a mix of connection speeds and I believe you can find similar functionality in many of the web test tools you will find in a freshmeat.net search.

Simulating "real life" is tough.

[Anonymous Coward]

The problems are never what you expect. After hypertuning the web server you may find that your SQL backend is causing a bottleneck. Or that something in an external, offline, transaction- finishing process is flaky/unreliable/slow. Or that one particular area used by one particular class of users is making their perceived response horribly slow, while the rest of the world notices no problems at all. One thing that has helped on an aging site I work with is to track percentage of "completed" actions - for example, the user should click pages 1/2/3/4/5, in that order. If 80% make it to #3 and 15% are getting to #4, that may reveal bottlenecks that ps and ab and top won't show you.