Segue Software SilkPerformer V is a load-testing tool designed to simulate the fluctuating usage demands of an e-business environment, and let you locate application errors that occur under extreme conditions. According to the company, the product improves the accuracy and performance of critical applications, so you don't waste time and resources down the road fixing costly errors that didn't appear until your application was stressed.

Load-based errors

SilkPerformer V verifies the content of Web pages, while simulating heavy loads to give you a realistic view of performance. (The "V" stands for "Verification Under Load.") It captures content errors that don't appear under small loads.

"When you're doing a stress test of an application," says Basil Harris, vice president of product marketing for Segue, "it's one thing to put it through its paces to find out if it will continue to perform at levels you expect when there are lots of users on it. But it's another thing to also determine whether the content coming back from a Web site -- for example, a price, a quote, or a page -- continues to be accurate as you stress the system."

"There are anomalous behaviors that can occur -- in a Web-based application, in particular -- when you have lots of people hitting the site at the same time and/or doing complex things. ... Unless you anticipate those kinds of loads and account for them in your application, you can get strange results."

Those problems can have various causes. For example, perhaps you've put too much stress on a back-end database server, or some piece of application logic fails under stress.

Harris gives the example of a brokerage company that ran into trouble because a heavily taxed financial application started to apply transactions to the wrong user's account. "This didn't show up in any testing they did ahead of time. It showed up when the customer asked, 'What happened to my money?'"

SilkPerformer V, therefore, lets you build testing scripts that simulate system stress and check for content errors as stress builds. You can customize these scripts to simulate what happens when a user comes to your site, and simulate different usage scenarios. For example, you can specify that users are inside your firewall, or that they're accessing your site over a T1 line.

Graphical analysis, resource efficiency

You could do this in the past, says Harris, but it was complex, and there were no graphical tools to help you.

SilkPerformer V comes with the Segue TrueLog Explorer component, which gives you visual root-cause analysis of errors. In addition, you can run tests through a graphical interface, without having to do manual scripting.

The combination of the user interface and TrueLog Explorer lets non-technical users follow the load testing workflow and predict and prevent application failures.

In addition, the product cuts down on the system resources consumed during the testing process. TrueLog Error lets you capture just the errors that occur, and bypass all of the irrelevant user activity. This makes it easier to scale to heavier simulation loads and not tax your system as you test, says Harris.

Flexibility

SilkPerformer V supports load testing for WAP applications and i-Mode applications. You can also use it to load-test applications built using SOAP, a key component of Microsoft's .NET initiative and other Web services platforms.

Cutting costs

Harris says the chief benefits are you get higher-quality applications and can design and launch them faster. In addition, because the graphical tools let "non-techies" run tests, you don't have to involve skilled programmers in the process.

Availability

Segue Software SilkPerformer V is available in several "flavors":

• Perpetual license (US$50,000) -- Lets you run any number of load tests, as long as you don't exceed 100 virtual users.
• Pay-per-use license ($18,000) -- This works like a telephone credit card. Segue sells you 5,000 virtual users, and decrements your credit every time you run a load test.
• Service -- Segue also offers hosted load testing, called SilkExpress.