Working with Domain Driven Design with Mongodb and an external service. Let's say we have two services Service A (for aggregate A) and Service B for aggregate B. Whenever an Aggregate A is created, a corresponding Aggregate B is also created. This is done synchronously via an API call to ensure real-time operations. In case the creation of Aggregate B fails, the creation of Aggregate A needs to be rolled back.
The Domain Event Aggregate_A_Created is fired once the Aggregate A is stored in DB (handled via ORM). Before the Aggregate B is created.
The problem I face is quite simple, if the Aggregate A was created, the event is fired but if the Aggregate B creation fails, the Aggregate A is deleted from the database but the Domain Event was fired that already signifies that Aggregate_A_Created. This might lead the system into an invalid state where other services think that Aggregate A exists but in reality it fails.
I can fire another event Aggregate_A_deleted but what if a service receives the Deleted event before the Created event?
I am stuck here, some insights would be great. Can I change the Spring Implementation to fire the domain event only when both operations have succeeded? I read that Spring Mongodb doesn't support Transactional calls
If Aggregate A and Aggregate B cannot be separated, should they not be parts of a common aggregate root?
If they are really separate, B should listen to A being created and only acknowledge that event, if B creation succeeds. This way - provided that you have persistent events - a B will be created even if the system goes down after A has been created and gets restored to that state.
Regarding transactions: as mongodb itself can handle transactions, don't let your choice of libraries limit you. If spring cannot do it, use the driver directly.