a practical introduction to event sourcing and cqrs
TRANSCRIPT
A practical introduction to Event Sourcing and Command Query Responsibility Segregation
CRUD
Create, Read, Update, Delete
CQRS
Command QueryResponsibility Segragation
Event Sourcing
Store all changes to the system, rather than it’s current state.
Event Sourcing
Store all changes to the system, rather than it’s current state.
Mathias Verraes (http://verraes.net)
Motivation for Event Sourcing
Expressivity
Distributed /event-driven architecture
Audit log*
Debugging
New representations / analysis
Easy storage
Commands
Do that! (imperative)
Command Handlers will handle commands. They don’t return a result, only accept or reject commands.
$commandHandler->handle($command);
Events
Domain Events: something interesting in the domain / business
(infrastructure) events: user clicked button, log has been rotated, file upload failed
Events are something which happened in the past
You can’t change the past, so events are immutable
Event Sourcing does not need a framework.
But Neos.EventSourcing helps you implementing Event Sourcing with Flow.
The sample domain
addBookToAssortment addBookToCatalog addBookToListOfProductsPeopleCanBuy ;-)
Live Demo 😱
Some special cases
Deleting a book
Media / assets / binary data
Flow accounts, …
Versioning events
Should you try it?
