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

Easy

[epsalon]

Post it on the front page of slashdot...

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.

New unit of site capacity

[GCP]

"By upgrading from IIS to Apache/mod_perl, we were able to increase our load capacity from 300 millislashdots to a full 1.2 slashdots while cutting costs by nearly two-thirds...."

Re:New unit of site capacity

[Kredal]

Let's see. 250,000 people come to Slashdot every day. We'll assume you get a story posted in the morning, right before everyone (well, nearly) gets to work, and they all log onto their favorite site (nonono, not pr0ns-r-us.com), and 1/3 of the users click on the link within an hour of it being up.

That's 83,000(rounded) views, if you have a single page with no pictures. I suppose we can use that as a basis, and people can calculate out from there, if they want to. So:

1 Slashdot (Sd) = 83,000 views (per hour).
1 CentiSlash (cSd)= 830 views
1 MilliSlash (mSd)= 83 views
1 MegaSlash (MSd)= 83 million views

The average high volume news site (CNN, ABC, Register) can probably withstand 2-3 Sds, while a potato powered, or C64 server could only withstand 10-20 cSds. Of course, the lower powered servers will have less to download, so a single Sd may be managable.

Again, this gets into how many pages/images Slashdot is linked to.

Further study is advised.

Apache comes with one

[Quixote]

Checkout Apache Test page. Apache comes with Flood, a profile-driven web server tester.

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.

Siege

[modecx]

I have had good luck with the neat little program called siege. It can stress a single URL, multiple URLs, follow links from a root URL (simulating an actual user), and have many multiple concurrent connections active. At the end, Siege can tell you all about the server performance, latency, etc.

I really like one of the other poster's idea about having a load tester read actual log files from Apache, then simulate real user activity. The only problem I can see with this method, is if you changed the layout of your site, all the program would get is a bunch of 404s. However, if one were so motivated, one could hack up such a thing relatively easy, I think. analog can parse Apache/httpd log files, could'nt be all that hard. Siege works well for me, though, so I'll stick with it.

The Grinder, again

[AdamInParadise]

Like a previous poster, I recommend The Grinder. I looked all around for a load testing tool. People usually recommend the Microsoft tool, but I don't do Microsoft. I tried JMeter and a bunch of other tools, but they never feel quite right. Most tools fall in two categories: either completly unscriptable or so scriptable that using a general-purpose script language would be faster.

Among (many) other things, The Grinder has a built-in proxy that allows it to record a browsing session and play it back later. Basically, you start the proxy, set your browser to use this proxy, browse your website, and get back a log of your actions complete with timings and POST values. One other cool features is that it let you define your own datasources so you can fill POSTs and GETs with custom data. Last but not least the author of the tool will personally answer your questions, albeit slowly.