J2EE application performance optimization

How to extract maximum performance from your J2EE Web applications

By Rahul Kuchhal, JavaWorld.com, 05/17/04

In today's world of larger-then-ever software applications, users still expect real-time data and software that can process data at blazing speeds. With the advent of broadband access, users have grown accustomed to receiving responses in seconds, irrespective of how much data the server handles. It is becoming increasingly important for Web applications to provide as short response times as possible. The most obvious and simple way to improve a Website's performance is by scaling up hardware. But scaling the hardware does not work in all cases and is definitely not the most cost-effective approach. Other solutions can improve performance, without extra costs for the hardware. This article provides some suggestions that prove helpful when trying to maximize a J2EE Web application's performance.

If you decide to try this article's recommendations, keep in mind this article provides suggestions only. Performance tuning is as much an art as it is a science. Changes that often result in improvement might not make any difference in some cases, or, in rare scenarios, they can result in degradation. For best results with performance tuning, take a holistic approach.

Overview

Figure 1 illustrates at a broad level how a J2EE application appears when deployed in a production environment. To get the best performance from a J2EE application, all the underlying layers must be tuned, including the application itself.

Figure 1. J2EE application architecture. Click on thumbnail to view full-sized image.

For maximum performance, all the components in Figure 1—operating system, Web server, application server, and so on—need to be optimized. This article will give a glimpse into tuning a J2EE application server, Web server, relational database, and your J2EE application. For maximum payoff from this article, follow these guidelines:

Set a goal: Before you begin tuning your J2EE application's performance, set a goal. Often this goal addresses the maximum concurrent users the application will support for a given limit on response times. But the goal can also focus on other variables—for example, the response times should not increase more than 10 percent during the peak hour of user load.
Identify problem areas: It is important to identify the bottlenecks when you start making changes to improve performance. A little investigation into problems might reveal the specific component that causes poor performance. For example, if the CPU usage on an application server is high, you will want to focus on tuning the application server first.
Follow a methodical and focused path: Once the goal is set, try to make changes that are expected to have the biggest impact on performance. Your time is better spent tuning a method that takes 10 seconds but gets called 100 times than tuning a method that takes one minute but gets called only once. In an ideal world, you test one change at a time before using it in a production environment. You make one change and stress-test it. If the change results in positive impact, only then will you make it permanent.

Identify bottlenecks

The goal of performance tuning is to identify bottlenecks and remove them. It is an iterative process. Once one area of the application improves, another area will become a bottleneck. You must repeat the cyclic process of first identifying the bottleneck, then resolving the bottleneck, then identifying the next bottleneck until the desired goal has been reached. You will need two kinds of tools that prove helpful in this process. First, you need stress tools that generate load for your application. Second, you need monitoring tools that collect data for various performance indicators.

Stress tools

Many different stress tools are available in the market today. Some of the popular ones are:

Mercury Interactive's LoadRunner
Segue's SilkPerformer
RadView Software's WebLoad

For a comprehensive list of stress tools see this article's Resources section. You must choose a tool that best fits your needs based on the tool's features and associated price tag. Some of the important features you should consider before choosing a tool are:

Support for a large number of concurrent Web users, each running through a predefined set of URL requests
Ability to record test scripts automatically from browser
Support for cookies, HTTP request parameters, HTTP authentication mechanisms, and HTTP over SSL (Secure Socket Layer)
Option to simulate requests from multiple client IP addresses
Flexible reporting module that lets you specify the log level and analyze the results long after the tests were run
Option to specify the test duration, schedule test for a later time, and specify the total load

For the sample tests mentioned in this article, LoadRunner was used.

Performance monitors

Using a monitoring tool, you collect data for various system performance indicators for all the appropriate nodes in your network topology. Many stress tools also provide monitoring tools. Windows OS also has a built-in performance monitor sufficient for many purposes. This Windows performance monitor can be started from the Administrative Tools menu, accessed from the Control Panel menu, or by typing "perfmon" in the Run window (accessed from the Start menu). You can display the performance counters data in real time, but usually, you'll want to log this data into a file so it can be viewed later. To log the data into a file, go to the Counter Logs selection in the left-hand side of the Performance window, right click with your mouse, and select New Log Settings as shown in Figure 2.

Figure 2. Windows performance monitor. Click on thumbnail to view full-sized image.

You can also set the file path/name for where the data should be logged, as well as a schedule of when to collect this data. It is possible to log the data and view it in real time, but the performance counters must be added twice—first, in the System Monitor link on the left-hand side and second, in Counter Logs, as shown above.

Many performance counters are available in Windows OS. The following table lists some of the important counters that you should always monitor:

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