Domain Events about domain-driven-hexagon

[Sairyss]

I mean when publishing events with eventBus.publish(new Event()) there is no option to await for all events to finish.
So, imagine that you have a situation like this:

const user = new User();
this.eventBus.publish(new UserCreatedEvent()); //  <- this will not wait for events to finish
await this.repository.save(user);
return user; // <- consumer of your api will get a user before published events are executed

Now lets say that you have event handlers somewhere listening for a UserCreatedEvent, for example you need to create a wallet for a user when a user is created, and save it to the db.
If you don't await for the publisher to finish executing all the events your function will return right after user is saved to the database, without waiting for a wallet creation.
It is reactive sure, but what if after saving a user your api/database crashes? Your wallet will never be created. Reactive events are good when you have a mechanism to retry sending an event in case of a failure (for example if you use message brokers like RabbitMQ), but NestJS CQRS event bus is in-memory, so in case of a crash/restart it will just lose all the events. Some events will be executed, some not. This means you will have inconsistent data everywhere.
On the other hand, when a publisher lets you await for all domain events to finish (which NestJS CQRS doesn't) you can include all those events in a single transaction and if one event fails none of the data gets persisted. Its all or nothing.
I hope this answers your question

[johannesschobel]

wouldn't it be good to add this kind of feature to the official NestJS CQRS package? What do you think @Sairyss