BUILDING RESPONSIVE AND SCALABLE WEB APPLICATIONS
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Copyright 2000 by Software Engineering Research and L&S Computer Technology, Inc.
Appears in Proceedings Computer Measurement Group Conference, Dec. 2000
Page 1 of 1
BUILDING RESPONSIVE AND SCALABLE WEB APPLICATIONS
Connie U. Smith, Ph.D.
Performance Engineering
Services
PO Box 2640
Santa Fe, NM 87504
(505) 988-3811
cusmith@perfeng.com
Lloyd G. Williams, Ph.D.
Software Engineering Research
264 Ridgeview Lane
Boulder, CO 80302
(303) 938-9847
boulderlgw@aol.com
Abstract
Responsiveness and scalability are important quality-of-service attributes for
Web applications. Web sites that are slow, either because of poor responsiveness or
lack of scalability, can produce customer dissatisfaction, loss of revenue and/or
productivity, and potentially more serious consequences. To avoid these problems, it is
important to know whether users will be able to access information in a timely fashion,
whether the hardware will be able to handle the load, and whether the system will scale
to meet projected demand before the system is deployed.
This paper describes how to apply the techniques of Software Performance
Engineering (SPE) to Web applications. We focus on using the SPE models to provide
decision support during the software architectural design phase because the decisions
made at that time have the largest effect on performance and scalability. A case study
illustrates the application of these techniques to a typical Web application.
1.0 Introduction
Responsiveness is an essential quality-of-
service attribute of Web applications. If your site is
slow in responding to user requests, your customers
will go elsewhere. Scalability is equally important for
these applications. A Web site can experience rapid
increases in traffic in response to advertising,
corporate announcements, or added functions. There
are numerous stories of web performance failures,
such as the Victoria’s Secret fashion show, the on-line
brokerage failure to provide service on heavy trading
days, and the EBay performance problems. These
performance failures result in: customer dissatisfaction
(the perception of poor performance will remain long
after you have corrected the problem); lost revenue
and/or productivity; and potentially more serious
consequences, such as lawsuits.
Many organizations worry about making
headlines such as those above if their Web application
fails to provide adequate responsiveness and
scalability. Organizations that don’t worry about
responsiveness and scalability often end up making
those headlines. To avoid these problems, it is
important that you be able to answer the following
questions before you deploy your Web application:
• Will your users be able to access information in a
timely fashion?
• Are your hardware and software capable of
supporting your projected load?
• Will your system scale up to meet projected
future demand?
The techniques of Software Performance
Engineering (SPE) allow you to answer these
questions and manage the performance of your
evolving Web applications [SMIT90a; SMIT01]. With
SPE you can:
• Improve responsiveness with quantitative
techniques that predict and manage software
performance and scalability.
• Select the right software and technical
architecture by predicting the performance of
middleware and server software options.
Software architectural decisions are the most
important ones you will make when designing your
Web application. It is vital to assess the impact of
these decisions on responsiveness and scalability
early in the development process, when it is easy to
make changes. If you wait until the application has
been completed and rely on performance testing only,
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