Scalability Is About Resource Economy

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There's always an upper limit to scalability, no matter how much hardware in the form of memory and processing power you place at the disposal of your application. Furthermore, if you design and build your application in such a way that it wastes resources, scalability might come at too high a price. So one of your tasks as a developer of scalable applications is to conserve processing resources. You shouldn't allow any user or component to subscribe to resources not needed at the moment.

Manufacturers save money by asking their suppliers to ship them parts just in time (JIT). The parts delivered according to this strategy should arrive at the factory hours, not days and certainly not weeks or months, before the factory needs them. The factory saves money in two important ways. It saves space because the parts can go directly from the unloading ramp into production rather than to a warehouse. It minimizes risk because the likelihood of buying more than the manufacturer actually needs is considerably reduced.

As application developers, we should strive toward the same economical use of resources. You, as a designer and developer, should never allow clients to activate server-based business objects until they have a purpose to fulfill. After fulfilling it, they should immediately and automatically deactivate themselves.

Resource Economy Is Our Main Goal

The main goal of our set of design patterns is to achieve this economic use of resources. We try to activate business objects just in time, and we try to deactivate them as soon as possible.

One of the most important goals of MTS was to help developers achieve an economical use of resources. MTS works best under the paradigm of just-in-time activation and as-soon-as-possible deactivation. In Windows 2000, MTS has been integrated into COM+. What used to be MTS components are now called configured COM+ components, a subject we'll cover in Chapter 15, "A COM+ Overview." Consequently, configured COM+ components also prefer to be activated late and deactivated as soon as possible.

In short, resource economy is one of the main reasons for us to rely completely on COM+ or MTS for our server-side objects!