Opinionated, distributed, event-driven state machines
Event-Sourcing is hard. In practice, one way to succeed with event-sourcing is to use events to drive distributed state machines in a microservice architecture. Specifically:
- Events are owned by a relevant microservice. There is no single, global event log.
- Events are broadcasted through some PubSub framework. Separate microservices update their event logs in response to changes in other microservices.
- Events are regulated by a state machine. Events must have rules that dicate whether they may follow other events in the stream and logic that controls how they aggregate state over time.
All of the above is very workable as long as the state machine logic is consistent over time. eventmachine is an attempt to codify these rules and introduce versioning semantics that create maintanable coherency.