How Take Action For "Side Effects"

[NecatiKaya]

Say suppose we have a MeetingCreatedDomainEvent, man pinpoint in DDD and event programming i think is how to handle side effects. I mean how to handle one change in domain/sub domain at other domains (domains in same module or other modules). When a MeetingCreatedDomainEvent is fired there might be a notification which corresponds to the domain event (Say suppose MeetingCreatedNotification) .A notification we can hava a notification handler. But what happens if i need to change two or more modules? Can there be only one notification with one handler only? Or one notification with multiple handlers? What is the suggested way

[AlmarAubel]

Both domain events and notification events can have multiple handlers — and that’s exactly the point. It keeps the system decoupled and scalable.

• Use domain events for internal coordination within a module. (handled in process)
• Use notification events for things outside the core domain (e.g., sending emails). (handle out-of-proces)
• Use integration events over a message bus to communicate between modules.

Example:

• MeetingCreatedDomainEvent → multiple internal handlers
• MeetingCreatedNotification → external side effects
• MeetingCreatedIntegrationEvent → published across modules

See also module integration

[NecatiKaya]

You cleared my mind, thank you @AlmarAubel

[waqasdotnet]

One thing which I didn't understand is that when ProcessOutboxCommandHandler is publishing Notifications why can't it also create IntegrationEvent at this point and publish them via EventBus. Why xxxPublishEventNotificationHandlers are publishing integration events to EventBus?

What if there is some error in xxxPublishEventNotificationHandlers, other modules will never receive any notification.

I think IntegrationEvents should be published as soon as we read them from OutboxMessages table.