CQRS & Event Sourcing in OLX

Transcript

1. CQRS Event Sourcing in OLX

2. CQRS

3. you can use a different model to update information than

   the model you use to read information http://martinfowler.com/bliki/CQRS.html „

4. Command Query Responsibility Segregation

5. Command Query Responsibility Segregation

6. new AddCredits($userId, $amount); Command

7. Command new AddCredits($userId, $amount); Query new GetCredits($userId);

8. Event Sourcing

9. http://www.martinfowler.com/eaaDev/EventSourcing.html „ ensures that all changes to application state are

   stored as a sequence of events

10. Not just can we query these events, we can also

    use the event log to reconstruct past states http://www.martinfowler.com/eaaDev/EventSourcing.html „

11. Commad Event Model Event Storage Event Bus Command Handler Listeners

    Read Storage Read Model Query

12. Commad Event Model Event Storage Event Bus Command Handler Listeners

    Read Storage Read Model Query Critical section - use transaction

13. Commad Event Model Event Storage Event Bus Command Handler Listeners

    Read Storage Read Model Query Critical section - use transaction Treat like temporary cache

14. That’s all

15. E-Wallet Credits; Invoices; Refunds

16. Wallet Credits Bonus Credits Refund Credits EXPIRE: X DAYS EXPIRE:

    X DAYS EXPIRE: X DAYS INVOICE: YES/NO INVOICE: YES/NO INVOICE: YES/NO

17. Wallet Credits Bonus Credits Refund Credits EXPIRE: NEVER EXPIRE: 90

    DAYS EXPIRE: 90 DAYS INVOICE: YES INVOICE: NO INVOICE: YES

18. Opis walleta w Polsce specyfikacja komenty enventy Commands

19. Add Wallet Credits Add Bonus Credits Add Refund Credits

20. Sub Wallet Credits Sub Bonus Credits Sub Refund Credits SubCredits

21. Opis walleta w Polsce specyfikacja komenty enventy Events

22. Wallet CreditsWasAdded Bonus CreditsWasAdded Refund CreditsWasAdded

23. Wallet CreditsWasSubtracted Bonus CreditsWasSubtracted Refund CreditsWasSubtracted

24. specyfikacja komenty enventy 7 commands 6 events

25. specyfikacja komenty enventy What about other stuff?

26. Commad Event Model Event Storage Event Bus Command Handler Listeners

    Read Storage Read Model Query ?

27. Broadway komponenty Broadway https://github.com/qandidate-labs/broadway

28. Auditing log whether commands were successful or not

29. CommandHandling Provides the interface and a CommandHandler base class for

    handling events

30. Domain domain abstractions of the Broadway framework including the aggregate

    root, domain messages and domain events.

31. EventDispatcher The component provides an event dispatcher interface and a

    simple implementation

32. EventHandling provides interfaces for an event bus and event listeners,

    but also an implementation of a simple event bus and an event bus that will record published events

33. EventSourcing Provides base classes for event sourced aggregate roots and

    entities, an event sourced repository implementation and testing helpers.

34. EventStore implementation based on doctrine/dbal to store events in a

    relational database and an in-memory implementation that is useful for using in tests

35. ReadModel provides storage for your read models, a projector implementation

    to create read models from event streams and testing helpers.

36. Repository Component providing an abstraction of the storage of aggregates.

37. Serializers provides a simple serializer interface and a serializer implementation

    based on "handwritten" serializers

38. Commad Event Model Event Storage Event Bus Command Handler Listeners

    Read Storage Read Model Query Broadway

39. Adding Wallet Credits

40. None
41. None

42. Credits Query

43. None
44. None

45. Lessons Learned

46. Small Steps Don’t try to CQRS/EventSource everything

47. Keep It Simple Avoid names like BonusCreditsWasSubtractedBecauseAdminHitSubtractBonusCr editsInAdminPanelEvent

48. Event Storming is not that easy as it sounds

49. It’s not RDBM Remember about analysts

50. Code changes Events handle changes to data, what about changes

    to code?

51. Synchronize Remember about synchronizing read layer - especially after fail

52. Commad Event Model Event Storage Event Bus Command Handler Listeners

    Read Storage Read Model Query Critical section - use transaction

53. Performance is not an issue - for this case

54. Timezone Agnostic Implement your own EventStore if you want timezone

    aware records

55. Our Team

56. Paid Features

57. Next challenge Open source Paid Features libraries with Hexagonal Architecture

    in mind

58. Team Lead PHP Dev Junior PHP Dev You ?

59. Łukasz Szymański Development Team Lead at @szymanskilukasz http://szymanskilukasz.github.io/ https://www.linkedin.com/in/szymanskilukasz https://twitter.com/szymanskilukasz