Introduction to Event Sourcing and CQRS

An Introduction to Event Sourcing and CQRS presented at 11º PHPSC InCompany Meetup

Transcript

1. 11º PHPSC InCompany
2. Guilherme Augusto Henschel a.k.a. Cenoura developer since 2009 working @ Nexaas
3. Notice ✘ this talk intent is to open your mind ✘ use these patterns carefully ✘ remember, there is no silver bullet
4. ORM Customer Memory Database Customer Account owns name address account Account accountNumber type balance
5. Event Sourcing
6. “ Event Sourcing ensures that all changes to application state are stored as a sequence of events. — Martin Fowler
7. AccountCreated id: 123 owner: Guilherme H. 1 DepositPerformed accountId: 123 amount: $50 2 WithdrawalPerformed accountId: 123 amount: $20 3
8. Pros ✘ complete log of every state change ✘ easy way to undo things ✘ testing, traceability and debugability ✘ business and data analysis of event streams ✘ immutability
9. Cons ✘ complexity ✘ time to get used to ✘ limited support from frameworks
10. When ✘ rich object-oriented domain models ✘ critical accountability and debugability ✘ version control for data ✘ data can give you competitive advantage ✘ building scaleable systems based on CQRS pattern
11. CQS Command Query Segregation
12. “ every method should either be a command that performs an action, or a query that returns data to the caller, but not both. — Bertrand Meyer
13. CQRS Command Query Responsibility Segregation
14. “ creating two objects where there was previously only one
15. Before
16. Improving
17. After
18. Pros ✘ scalability ✘ flexibility ✘ reduced complexity ✘ concentrate on domain/business
19. Cons ✘ complexity
20. When ✘ task based user interfaces ✘ complex data processing ✘ disparity in reads and writes
21. Event Sourcing + CQRS
23. Libs/Components ✘Broadway - https://github.com/broadway/ broadway ✘Prooph - http://getprooph.org/
24. thanks! guilhermeaugusto.com.br
25. References ✘ Greg Young talk - https://www.youtube.com/watch?v=JHGkaShoyNs and https://cqrs.files.wordpress.com/2010/11/cqrs_documents.pdf ✘ Johannes Seitz talk - https://ookami86.github.io/event-sourcing-in- practice/ ✘ Martin Fowler articles - https://martinfowler.com/eaaDev/ EventSourcing.html and https://martinfowler.com/bliki/CQRS.html ✘ Marco Pivetta talk - https://www.youtube.com/watch?v=8NuHNtwjync ✘ http://www.cqrs.nu/ ✘ https://speakerdeck.com/owolf/cqrs-for-great-good ✘ https://speakerdeck.com/mattketmo/cqrs-and-event-sourcing