Aggregate event streams

[adriano-di-giovanni]

I'm submitting a...

[ ] Regression 
[ ] Bug report
[x] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead post your question on Stack Overflow.

Current behavior

Persisting events using external stores such as Event Store happens by appending them to a stream. The stream groups all events related to a particular instance of an aggregate root. The stream name usually is <AggregateRoot>-<id>.

At the moment, the stream name/id information has to be bundled with the event.

Expected behavior

It would be great to introduce the concept of stream name/id at the AggregateRoot level

export abstract class AggregateRoot<EventBase extends IEvent = IEvent> {
  // ...
  protected get streamId(): string {
    return void 0
  }

  publish<T extends EventBase = EventBase>(event: T, streamId?: string) {}
}

Such change would also impact

• the IEventBus and IEventPublisher interfaces
• the EventPublisher

If streamId is optional, the change is non-breaking.

[redaLaanait]

Wrapping the event and passing the streamId as metadata to the event envelope (which also extends IEvent) may solve the problem.

the event handler can be decorated as follow:

@EventsHandler(Envelope<OriginalEvent>)

(just started looking into nestjs and CQRS module... hope I'm not messing up)