Mark Richards

relay races, once a runner hands off the baton, she is done with the race. This is also true with the broker topology: once an event processor hands off the event, it is no longer involved with the processing of that specific event

The broker topology tends to be easier to deploy than the mediator topology, primarily because the event mediator component is somewhat tightly coupled to the event processors: a change in an event processor component might also require a change in the event mediator, requiring both to be deployed for any given change

Since event-processor components are single-purpose and completely decoupled from other event processor components, changes are generally isolated to one or a few event processors and can be made quickly without impacting other components

Testing is also complicated by the asynchronous nature of this pattern

the ability to perform decoupled, parallel asynchronous operations outweighs the cost of queuing and dequeuing messages

Scalability is naturally achieved in this pattern through highly independent and decoupled event processors

The microkernel architecture pattern allows you to add additional application features as plug-ins to the core application, providing extensibility as well as feature separation and isolation

The microkernel architecture pattern consists of two types of architecture components: a core system and plug-in modules

The plug-in modules are stand-alone, independent components that contain specialized processing, additional features, and custom code that is meant to enhance or extend the core system to produce additional business capabilities

Generally, plug-in modules should be independent of other plug-in modules, but you can certainly design plug-ins that require other plug-ins to be present