What are domain events?
Earlier in this book, we discussed the use of DDD as a design pattern that helps us to scope the different services that might be required as we develop our microservices application. Events can be employed in the implementation of this pattern to help us to model expected outcomes within our bounded contexts. Events are scoped based on the ubiquitous language that has been established within the bounded context and is informed by decisions within the domain.
Within the domain, aggregates are responsible for creating domain events and our domain events are usually raised based on the outcome of some user action, or command. It is important to note that domain events are not raised based on actions such as the following:
- Button clicks, mouse moves, page scroll events, or simple application exceptions. Events should be based on the established ubiquitous language of the bounded context.
- Events from other systems or outside of the current context...
