Event-driven architecture is a software design pattern that enables an organization to detect “events” or important business moments (such as a transaction, site visit, shopping cart abandonment, etc) and act on them in real time or near real time.
Events an event is a data point to represent state changes in a system.
Each service publishes an event whenever it updates its data. Other services subscribe to events. When an event is received, a service do it something.
Event Sourcing idea is simple: our domain is producing events that represent every change made in system. If we take every event from the beginning of the system and replay them in the initial state, we will get to the current state of the system. It works similarly to transactions on our bank accounts; we can start with an empty account, replay every single transaction and (hopefully) get the current balance.
The Saga design pattern is a way to manage data consistency across microservices in distributed transaction scenarios. A saga is a sequence of transactions that updates each service and publishes a message or event to trigger the next transaction step. If a step fails, the saga executes compensating transactions that counteract the preceding transactions.
The Publish/Subscribe pattern is an architectural design pattern that enables publishers and subscribers to communicate with one another. In this arrangement, the publisher and subscriber rely on a message broker to send messages from the publisher to the subscribers. Messages (events) are sent out by the host (publisher) to a channel, which subscribers can join.
- All events is immutable (+/-)
- Easy make a rollback
- Hard to support