COM & .NET Component Services

Instance Management and Scaling

Being smart about the way you allocate your objects to clients is the key to scalability in a modern distributed system. Simple algorithms can be used to govern when and how expensive objects that have access to scarce resources will actually service a client request. In distributed-systems terminology, these algorithms and heuristics are called instance management. COM+ refers to instance management as activation .

COM+ provides every configured component with access to ready-made instance management services. Every COM+ component has on its properties page an Activation tab that lets you control the way objects are created and accessed (see Figure 3-3). You can use COM+’s two instance management services, object pooling and JITA, individually, or combine them in a very powerful way. Neither technique is a COM+ innovation. What is new about COM+ is the ease with which you can take advantage of the service. That ease allows you to focus your development efforts on the domain problem at hand, not on the writing of instance management plumbing.

Figure 3-3.  The COM+ component’s Activation tab