So, what are the details of performance modeling? It's really comes down the information movement and services.

Information Movement Modeling, typically asynchronous in nature, means we're attempting to simulate how information moves from point to point, point to many points, or many points to many points. Based on the information we accumulated we know the:

Information production rate from a service
Information consumption rate from a service

For example, an instance of a service is able to produce 52 messages (or similar groupings of information) per second...the source service. An instance of a service is able to consume 34 messages per second...the target service. This is a simple point-to-point relationship, but keep in mind that multi-points to multi-points are always possible, and those are a bit more complex to model since you have to determine patterns of movement between multiple points vs. all messages produced by a single service that are consumed by another.

Moreover, keep in mind transformation and routing latency is typically an issue here as well, and needs to be modeled along with consumption and production. You should have test data from these services, but the performance of transformation and routing services will be largely dependent upon the complexities of the transformations and logic associated with the routing. What many do when creating performance models is to model very complex, complex, and simple transformation scenarios, and the percentages of each.

Service Invocation Modeling, typically more synchronous in nature, means we're attempting to determine the number of times a service is able to provide a behavior (application function) in an instance of time, typically a second.

For instance, you may have a service that provides a risk calculation for the insurance business, and is perhaps abstracted into several different applications (composites). We know through testing that each composite can invoke the service up to 100 times a second before it hits a saturation point, meaning the performance of the service quickly diminishes as additional load is placed upon it. This saturation number plugs into the model, as well as the number of applications that are abstracting this service. You have to model all of these services in the same way.

Making solutions scale is nothing new. However, the SOA technology and approaches recently employed are largely untested with higher application and information and service management traffic loads. SOA implementers were happy to get their solutions up and running, yet, in many cases, scalability is simply not a consideration within the SOA, nor was load testing or other performance fundamentals. We are seeing the results of this neglect now that SOA problem domains are exceeding the capacity of their architectures and the technology. It does not have to be this way.

Posted by Dave Linthicum on June 8, 2006 06:42 AM