O'Reilly - Java Message Service

Chapter 7. Deployment Considerations
Java Message Service
An enterprise application's performance, scalability, and reliability should be among the
foremost concerns in a real deployment environment. The underlying messaging
middleware is critical to that environment.
7.1 Performance, Scalability, and Reliability
Every JMS vendor claims to be the fastest in the marketplace. Some claim to be fast and
scalable to thousands of clients. It is hard to take any one vendor's word for having the
fastest and most scalable product. Different application architectures have different
demands. The industry has no accepted messaging benchmark. Thus, the proof of any
vendor's claims lies in your own testing and measurement.
Performance and scalability are terms commonly used together, but they are not
interchangeable. Performance refers to the speed at which the JMS provider can process a
message through the system from the producer to the consumer. Scalability refers to the
number of concurrently connected clients that a JMS provider can support. When used
together, the terms refer to the effective rate at which a JMS provider can concurrently
process a large volume of messages on behalf of a large number of simultaneously
connected producers and consumers. The distinction between performance and scalability,
as well as the implications of what it means to combine them, is very important, as you
will soon see. A simple test using one or two clients will differ drastically from a test using
hundreds or thousands of clients. The following section is intended to be used as a guide to
help with performance and scalability testing.
7.1.1 Determining Message Throughput Requirements
Before you embark on your performance and scalability testing effort, consider what you
are trying to accomplish. Since any particular vendor may do well with one scenario and
not so well in others, the makeup of your application is important to define. Here are some
key things to consider:
• The potential size of the user community for your application. While this may be
hard to project, it is important to try to predict how it will grow over time.
• The average load required by the application. Given a total size of the user
community for your application, how many are going to be actively using it at any
given time?
• The peak load required by the application. Are there certain times of the day, or
certain days in a month, when the number of concurrent users will surge?
• The number of JMS client connections used by the application. In some cases, the
number of JMS clients does not correspond to the number of application users.
Middleware products, such as EJB servers, share JMS connections across
application clients, requiring far fewer JMS client connections than other
applications. On the other hand, some applications use multiple JMS connections
per client application, requiring more JMS client connections than users. Knowing
the ratio of users to JMS clients helps you determine the number of messages being
processed per client.
108