Let's say I have a system to which I can upload documents via an API. There are three services:
- the
UploadService- responsible for providing a HTTP endpoint - the
StorageService- responsible for storing uploaded documents - the
FileCabinet- responsible for managing a file cabinet (e.g. categories, hierarchy, etc.)
I'm trying to learn more about event-driven architecture, and now I am trying to come up with one.
The UploadService can receive a command UploadCommand and emits a DocumentUploaded event once it created a
unique identifier for the uploaded document.
The StorageService listens for the DocumentUploaded event. Once it receives such an event, it creates a StoreDocument
command and handles it. The outcome is a DocumentStoredEvent.
The FileCabinet listens also for DocumentUploaded. Once it receives such an event, it updates its state to include
the uploaded document. The outcome is a DocumentFiledEvent.
What I don't get is, that when I would try to replay the events of the system, I would get duplicate events, since the services themselves trigger events. Am I missing some concepts here?
