Rethink your architecture with CQRS

devNetNoord 3, sessie 2

Transcript

1. Rethink your architecture with CQRS Pieter Joost van de Sande Passionated software developer, Atos Email: pj@born2code.net @twitter: pjvds
2. This is meant to be a take away!
3. Architecture
4. Architecture Presentation Domain Data
5. Presentation Domain Data
6. model Domain Driven Design Eric Evans - 2003
7. The value of a structured Model
8. Who believes in this?
9. Structured models are always created from a single viewpoint!
15. A model can only be optimized for one thing… and one thing only!
16. Presentation layer Data layer Domain layer Send DTO Send DTO Map DTO Map DTO Write data Write data Map DTO Write data Write data Send DTO Request DTO Map DTO Request DTO Map DTO Query data Query data Request data Map DTO Query data Query data Request DTO Send update Update screen
17. TWO FUNDAMENTALS
18. Information
19. Transitions
20. WRITING != READING
21. From 3-tier to CQRS Presentation layer Domain layer Data layer
22. Presentation layer Domain layer Data layer Just re-order the tiers
23. Presentation layer Domain layer Data layer Switch dependency
24. Presentation layer Domain layer Data layer CQRS! Query side Command side
25. FROM CONCEPT TO ARCHITECTURE HERE WE GO!
26. User interface
27. Demand for information
28. User interface Read side
29. We read a lot
30. We have multiple screens to fill
31. Data should be close to us
32. Relational databases are sub optimal for view data!
33. SELECT CCUS.CUST_FIRST_NAME , CCUS.CUST_LAST_NAME , CINT.CUST_INTEREST_RANK , CILO.CUST_INTERST FROM CUST_CUSTOMER AS CCUS , CUST_INTEREST_LOOKUP AS CILO , CUST_INTEREST AS CINT WHERE ( CCUS.CUST_CITY = 'Singapore' AND CCUS.CUST_PROV_STATE = 'Singapore' AND CCUS.CUST_CODE IN ( SELECT COHE.CUST_CODE FROM CUST_ORDER_HEADER AS COHE , CUST_ORDER_STATUS AS COST WHERE ( COHE.CUST_ORDER_DATE >='2009-01-01 00:00:00.001' AND COST.CUST_ORDER_STATUS IN( 'Shipped', 'Back-ordered', 'In-process' ) AND COHE.CUST_ORDER_STATUS_CODE = COST.CUST_ORDER_STATUS_CODE ) ) AND CCUS.CUST_CODE = CINT.CUST_CODE AND CINT.CUST_INTEREST_CODE = CILO.CUST_INTEREST_CODE ) ORDER BY CCUS.CUST_LAST_NAME ASC , CCUS.CUST_FIRST_NAME ASC , CINT.CUST_INTEREST_RANK ASC
34. Bottom line • Getting data should be simple – select * from x where y • Examples: – Get all products of user X – Get total price of all orders of month May
35. User interface Read side
36. Read side User interface Read databases
37. Read side User interface Read databases Facade
38. Read side User interface Facade Read databases DTO’s
39. Demand for change
40. I want to tell the system something
41. Read side User interface Facade Read databases DTO’s Write side
42. User interface Commandhandlers Read databases Read side commands DTO’s Write side Facade
43. Commands • Simple message contains all info needed • Lower coupling (law of demeter) • Causes a state transition • Contains the intend of the user • Exists in a bounded context • Examples: – AddProductToShoppingCart – PurchaseOrder – MoveUserToNewAddress – CorrectAddressForUser – FinalizeOrder
44. Commands example Create Cart Add item Add item Add item Remove item Purchase
45. Users don’t make changes for nothing, intent is important!
46. Change has intent • Users don’t make changes for nothing • This intent has value! Correct the address for user X Customer X moved to new address VS.
47. User interface Commandhandlers Read databases Read side commands DTO’s Write side Facade
48. User interface Commandhandlers Read databases Read side commands DTO’s Domein Write side Repository Facade
49. Event Sourcing
50. Events • Simple message that describes an event • Contains intent • Contains all the data related to the event • Past tense CustomerMoved { CustomerId, NewAddress }
51. Transitional flow
52. User interface Commandhandlers Read databases Read side commands DTO’s Domein Write side Repository Facade
53. User interface Commandhandlers Read databases Read side commands DTO’s Domein Write side Repository Facade
54. Event store • Contains all domain events • Does not need to be relational • Write are *awesomely* fast! • Rock solid audit log • Read models can (re)build themself of it • The domain uses it to get the current state • Can be used to build any structural model you want!
55. User interface Commandhandlers Read databases Read side commands DTO’s Domein Write side Repository ? Facade
56. User interface Commandhandlers Repository Event bus Read databases Write side Read side events commands DTO’s Domein Facade
57. User interface Commandhandlers Repository Event bus Denormalizers Read databases Write side Read side events events events commands DTO’s Domein Facade
58. Application flow
59. Wrap up • Optimize for reading and writing • Makes changes part of the problem domain • Free rock solid audit log • Capture the intent of changes • Allow multiple read models
60. Thank you! You’ve been a great audience!