Chapter 13 – Determining Individual User Data and Variances

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- J.D. Meier, Carlos Farre, Prashant Bansode, Scott Barber, Dennis Rea


Contents

Objectives

  • Learn how to determine realistic durations and distribution patters for user delay times.
  • Learn how to incorporate realistic user delays into test designs and test scripts.
  • Learn about key variables to consider when defining workload characterization.
  • Learn about the elements of user behavior that will aid with modeling the user experience when creating load tests.


Overview

This chapter describes the process of determining realistic individual user delays, user data, and abandonment. For performance testing to yield results that are directly applicable to understanding the performance characteristics of an application in production, the tested workloads must represent the real-world production environment. To create a reasonably accurate representation of reality, you must model users with a degree variability and randomness similar to that found in a representative cross-section of users.


How to Use This Chapter

Use this chapter to understand how to model variances such as user delays, user data, and user abandonment so that your workload characterization will create realistic usage patterns, thus improving the accuracy of production simulations. To get the most from this chapter:

  • Use the “User Delay” section, along with the sections that follow, to understand the key concepts of user delay modeling and its impact on workload characterization.
  • Use the “Determining Individual User Data” section to understand the key concepts of user data and its impact on workload characterization.
  • Use the “User Abandonment” section to understand the key concepts of user abandonment and its impact on workload characterization.


User Delays

The more accurately users are modeled, the more reliable performance test results will be. One frequently overlooked aspect of accurate user modeling is the modeling of user delays. This section explains how to determine user delay times to be incorporated into your workload model and subsequently into your performance scripts.


During a session, the user can be in a number of different states — browsing, logging onto the system, and so on. Customers will have different modes of interacting with the Web site; some users are familiar with the site and quickly go from one page to another, while others take longer to decide which action they will take. Therefore, characterizing user behavior must involve modeling the customer sessions based on page flow, frequency of hits, the amount of time users’ pause between viewing pages, and any other factor specific to how users interact with your Web site.


Consequences of Improperly Modeling User Delays

To ensure realistic load tests, any reasonable attempt at applying ranges and distributions is preferable to ignoring the concept of varying user delays. Creating a load test in which every user spends exactly the same amount of time on each page is simply not realistic and will generate misleading results. For example, you can very easily end up with results similar to the following.

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