What is Event Source pattern?
The Event Sourcing pattern defines an approach to handling operations on data that’s driven by a sequence of events, each of which is recorded in an append-only store. The events are persisted in an event store that acts as the system of record (the authoritative data source) about the current state of the data.
What is Event Sourcing pattern in Microservices?
Event sourcing persists the state of a business entity such an Order or a Customer as a sequence of state-changing events. Whenever the state of a business entity changes, a new event is appended to the list of events. Since saving an event is a single operation, it is inherently atomic.
What is the difference between event driven and Event Sourcing?
Event sourcing is a much more special term, referring to systems where the whole application state is stored as a sequence of events. A well-known popular class of examples are transactional database systems, which store any state changes in a transaction log. Here, the term “event” refers more to “state change”, not only to “notification”.
Which is an example of Event Sourcing in microservices?
For example, a service that participates in a saga needs to atomically update the database and sends messages/events. Similarly, a service that publishes a domain event must atomically update an aggregate and publish an event.
When to use the CQRS and Event Sourcing pattern?
The CQRS pattern is often used along with the Event Sourcing pattern. CQRS-based systems use separate read and write data models, each tailored to relevant tasks and often located in physically separate stores.
How does event sourcing based business logic work?
Event sourcing-based business logic consists of loosely coupled business entities that exchange events. This makes it a lot easier to migrate from a monolithic application to a microservice architecture. It is a different and unfamiliar style of programming and so there is a learning curve.