Chapter 14: Testing Tomcats Performance

Overview

Before you can confidently move your test server into production, meaning that it will be completely open to the elements, you have to have some idea of how it will respond to heavy usage. Ignorance is no defense in this situation; you must be sure of your server’s ability to cope with real life. The most effective way of doing this, bar having hundreds of third-world offshore testers bombard the server, is to run an automated load test.

An automated server load test simulates client requests so that a server is exposed to large amounts of activity in an environment you control. Load testing therefore helps you understand the scalability and performance limits of your server before it’s exposed to a heavy production load.

Server load testing tests the scalability of the server and thus the ability of the system to handle an increased load without degradation of performance or reliability. Scalability is how well a solution to a problem will work when the size of the problem increases. In the case of Web applications, scalability is the ability of the server to handle the jump from a small number of clients to a large number of clients. This usually involves the addition of hardware, though a well-configured system is the first line of defense. Scalability is intrinsically linked to performance, and a scalable system is one that has an increase in performance proportional to the new resources added, be they network equipment, high-performance databases, bandwidth, or hardware.