WebSphere Studio Workload Simulator overview

With the rapid evolution of e-business and the increasingly fierce competitive environment of reaching customers, suppliers, and other business entities, enterprises must produce more sophisticated and more reliable Web applications.

Through their Web sites and Web applications, enterprises have the ability to participate in the global economy by reaching a vast audience and conduct business worldwide around the clock. The Internet has been a catalyst for more efficient business transactions.

As e-business becomes more routine, however, customers’ expectations rise.

Web applications that exhibit slow response times will encourage potential customers to defect to a competitor’s Web site, especially now that the

WebSphere Studio Workload Simulator helps you deploy your Web applications with no concern for questions like: Does your Web site have enough capacity to handle its busiest days? Will you lose potential customers because your Web application is too slow or failed to complete that critical transaction? Are you concerned about your e-business becoming the major Internet news event?

2.2.1 IBM WebSphere Studio Workload Simulator for z/OS and OS/390

WebSphere Studio Workload Simulator simulates large numbers of “virtual users” and generates Web traffic to validate the performance of the Web-serving environment when confronted with production-level loads. Workload Simulator can also be used to perform quality assurance on Web applications and to test the functionality of Web servers.

2.2.2 Scalable test tool

Workload Simulator consists of two components: a Controller and an Engine. For high scalability, Workload Simulator’s Engine, which generates the load used during load-testing, is installed on a zSeries server. The load generated by the Engine can be used to test any Web-serving environment (that is, the

environment to be tested is not limited to z/OS). Workload Simulator supports multiple Engines.

2.2.3 Test functions accessible through the Windows® interface

Users interface with Workload Simulator through the Controller. This component resides on a Windows workstation and offers a Windows graphical user interface (GUI) for managing all aspects of the load-testing process: Test scripts can be created and edited; simulation runs can be set up, executed and monitored; and test results can be analyzed without leaving the Windows GUI.

2.2.4 Capture, playback, analyze

With Workload Simulator, the load-testing process can be summarized in three simple steps:

1. Users capture their actions during a Web session to produce a test script.

2. The script is played back through the environment to be tested.

3. Analysis is performed on the test results.

Capture

Test scripts are automatically generated by a capture function as the user navigates through a Web session. The capture function, launched with a simple click of the mouse, records the session’s Web traffic and turns it into a test script ready for immediate playback. If needed, you can add more complex

programming functions (such as weight distribution and looping) to the test script to mimic the actions of a group of real users. You can define sections of a test script as transactions for further monitoring and analysis.

To make simulations as realistic as possible, a load-testing tool must imitate the multiple possibilities that occur in real life and allow for variable content. For instance, not all users of an e-commerce Web site will have the same logon IDs or passwords, nor would they choose to purchase the same items, or have the same credit card number. Workload Simulator allows variable content to be incorporated into test scripts. Cookies, which are an example of variable content, are supported.

Playback

For maximum flexibility during execution, several runtime parameters can be set:

Whether the test should be repeated a specific number of times, or should run until manually stopped, or should run for a specific time period; and the number of “virtual users” to be simulated. To simulate real-life conditions, various delay times can be specified, for example delays between the virtual users as they go online (not all users log on at exactly the same instant), delays between Web pages, and between the elements of a Web page.

Analysis

After the test script has been defined and the simulation launched, the test can be monitored in real time during execution. You can monitor a test either through the Controller’s Windows GUI or through a Web browser. This remote monitoring capability is especially helpful for extended runs (for example, over a weekend), as it obviates the need for test personnel to be present at the test site.

In addition to its real-time monitoring and analysis tools, Workload Simulator also provides a graphing tool to help you create more in-depth analyses of your Web applications. Workload Simulator can graph various performance characteristics against the number of simulated users or against time. Response time, data throughput, throughput of page elements, and CPU or memory utilization are available for plotting.

For in-depth analysis of test results, different levels of logging of the test activity are possible and the HTTP activity of each simulated client can be traced.

Maintaining security during simulations

Workload Simulator supports Secure Sockets Layer (SSL) security protocol and handles capture and playback through a SOCKS firewall. These features help you maintain the same level of security in your testing environment that you strive for in your production environment.

Part 2

Workload Simulator