264 CHAPTER 10 JAVA EE PERFORMANCE ASSESSMENT (Affordable web hosting)
264 CHAPTER 10 JAVA EE PERFORMANCE ASSESSMENT Assessing Usage Patterns After you have set up your preproduction environment, the next major task you are faced with performing is a usage pattern assessment, to understand what your users are doing and in what balance they are doing it. The usage pattern assessment again refers to identifying balanced and representative requests; your tuning efforts are only as good as the load you send against your environment. Balanced and representative requests were required for performance tuning and capacity assessments and they are also required for performance assessments inside a preproduction environment. Without balanced and representative requests you may waste time tuning code that is seldom executed, and you might miss code that experiences significant performance issues when subjected to usage patterns that do not match your tests. Access log analyzers and user experience monitors can help you understand users behaviors. Web servers can be configured to record all requests made against them, and typically these requests are stored in a file named access.log, although the storage location can vary among vendors. An access log analyzer can parse this log file and display the top requests as well as report the frequency of each request. From this analysis, you can better design your load scripts to mimic your end users behavior. The difficulty that parsing access logs presents is that access logs report only URL requests and not parameters passed to those URLs in other words, access logs are not application aware; they are only URL aware. User experience monitors, on the other hand, are physical devices that sit on your network and watch requests as they happen in real time. Typically, you can preconfigure them with knowledge about your application so they re able to identify application functionality as opposed to simply reporting URLs. Another difference between access logs analyzers and user experience monitors is that access logs do not typically report request response times, but user experience monitors do. Not only do user experience monitors report response times, but also they can be configured to fire alerts (for example, send e-mails or even launch application processes) when SLAs are exceeded. It is worth noting that access log analyzers are mostly used by marketing departments to identify user demographics and behavior as well as assess the efficacy of marketing dollars. An access log analyzer attempts to answer the following questions: What path did the user get to a particular page? What types of advertising, such as banners, have been effective? What part of the country/world is the user located? What are the most popular pages/documents on the site? Therefore, with respect to assessing user behavior, you do not need the most expensive log analyzer you really need only answers to the following questions: What are the top pages being viewed? In what order are users visiting pages? (You determine this by tying together user requests by IP address and aggregating log entries into approximate transactions.) What are the average think times between requests within a transaction? What are the average think times between transactions?
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