Pattern: Domain event
patternFrom Domain-Driven Design (DDD).
Context
A service often needs to publish events when it updates its data. These events might be needed, for example, to update a CQRS view. Alternatively, the service might participate in an choreography-based saga, which uses events for coordination.
Problem
How does a service publish an event when it updates its data?
Solution
Organize the business logic of a service as a collection of DDD aggregates that emit domain events when they created or updated. The service publishes these domain events so that they can be consumed by other services.
Related patterns
- The Saga and CQRS patterns create the need for this pattern
- The Aggregate pattern is used to structure the business logic
- The Transactional outbox pattern is used to publish events as part of a database transaction
- Event sourcing is sometimes used to publish domain events
See also
- My book Microservices patterns describes this pattern in a lot more detail.
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