Basic introduction to Event Sourcing and CQRS concepts. How to implement it with Axon framework.

1. Introduction to Event
Sourcing,CQRS and Axon

2. About me

3. CROZ

4. How do we develop
software?

7. Perhaps a different
approach?

8. Event Sourcing

9. Event Logging
≠
Event Sourcing

10. Current State

11. Banking
Healthcare
E-Commerce
…

12. What are Events?

13. Banking domain:
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E-commerce domain:
•
•
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•

14. How do they look
like?

15. Current State Model

16. Order
Created
Item
Added
Payment
Method
Selected
Shipping
Address
Provided
Order
Placed
Timeline

17. Item Added
Order Created
Payment Method Selected
Shipping Address Provided
Order Placed
Event Store

18. Just another way of storing
information.
Data is append only
Data is immutable
Is there more to it?

20. „Apps age like fish,
data ages like wine”

21. Event Sourcing benefits

22. Command
Query
Responsibility
Segregation

23. 1
Query
Handler
Client
32
Event
Store
57
67
87
57
67
87
1
32
Projection
Projection
Projection
Projection
Projection
Projector
Projector
Projector
Projector
Projector

24. 1
Query
Handler
Client
32
Event
Store
57
67
87
87
Projection
Projection
Projector
Projector
087

25. COMMANDS

26. Events (past tense)
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•
•
•
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Commands (imperative)
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•
•
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27. AGGREGATES

28. Events
•
•
•
Aggregates
•
•
•
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•

29. Command
Handler
Client
1
3
Event
Store
2
2
1
Aggregate
Command
Accepted?
agg_id=2 agg_id=2

30. Best practice

31. Client Event
Store
Command
Handler
Query
Handler
EventCommand
EventQuery
Aggregate

32. Conclusion

33. Is there a framework?

34. AXON FRAMEWORK

35. WRITEREAD

36. def depositMoney(DepositMoneyCommand cmd) {
commandGateway.send(cmd)
}
@CommandHandler
void handle(DepositMoneyCommand cmd){
//validate command
apply(new MoneyDepositedEvent())
}
@EventSourcingHandler
void on(MoneyDepositedEvent event) {
//reload aggregate state
}
@EventHandler
void on(MoneyDepositedEvent event) {
// update generate projection
}

38. 1.Step – Define API

39. 2.Step – Implement a test

40. 3.Step – Implement write side

41. 4.Step – Implement read side

42. Lessons Learned
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43. Questions?