Friday, May 15, 2009

Tool Of The Day:

Load testing your web app is always one of those tasks that's really easy to push off. I find it's really hard to do well. On one hand, you can use tools like Apache's AB to easily stress your server. But, the stress your putting it under is pretty unrealistic.

And then there are tools like LoadRunner that will do the job right, but are an ordeal to setup and run. Oh, and they are expensive enough that they won't even list the price on the website. Though, in all fairness, my main experience with LoadRunner was watching the UI team of AmazingMedia wrestle with it to load test the AdVariant many years ago. Things must have improved since then.

Needless to say, I was not optimistic about finding a load testing tool for one of my clients. But, luckily, my fears weren't realized as I found

LoadImpact is part of a new generation of load testing tools. They are built on cloud computing, and as such, have access to as much power as you'd like to hurl at your website. A few of the features that I like about LoadImpact in particular:

  • A free option that allows you to run a useful test.
  • Paid tests that are relatively inexpensive and you can pay by the day or month. There was just something reassuring about spending $9.00 to try out their service.
  • All tests get a permalink that's public and sharable. This makes sharing results a snap.
  • With a paid account, you can choose from among a simple 1 page tests, or you can choose to script multi page tests.
  • The scripts can be hand edited if you're into that sort of thing.
  • Tests a relatively realistic, downloading content off of the page as a browser would and providing think times.
  • The graphs are pretty.
  • There a nice little case study to read.
  • They have the chutzpah to list other load testing services in their knowledge base. Nice move, it shows confidence.

As for downsides - I did occasionally run into issues where tests weren't allowed to run unless I upgraded. But, I wasn't specific limits I was running into were. Also, I wish I knew more about the simulation of the client. For example, is it observing the expires or last-modified headers? Will it handle gzip encoding? But these were minor issues considering what I was getting.

Is the service perfect? Of course not. But for $9.00, instant access, and mostly realistic tests - I'll take it.

If you're doing the site testing thing, you should also check out's Anazlyer and yslow.

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