CQRS, or did you mean CARS?

Everything you would want to discover when you're googling for CQRS for the first time. From general OOP principles to CQRS and Event Sourcing

Transcript

1. CQRS DID YOU MEAN CARS?
2. STIJN VANNIEUWENHUYSE @STIJNVNH ONE AGENCY - AUSY BELGIUM SOFTWARE DEVELOPER TDD, DDD, CQRS, ES & PHP
3. SOME REMARKS I know where I'm heading I don't know where I'll arrive I have assumptions about your knowledge I want to know if my assumptions were correct I try to answer every question I want to be stopped when something is not clear I want to be stopped when it has been long enough I want to know if you don't agree I know the examples are over-simplified I want to know if there are mistakes in my slides ;-)
4. SOFTWARE WHY DO WE WANT SOFTWARE?
5. VALUE
6. STATE
7. BEHAVIOUR
8. FLEXIBLE
9. SOFTWARE HOW DO WE BUILD GOOD SOFTWARE?
10. ABBREVIATIONS FTW! TDD BDD DDD GO4 SOA OOP
11. OBJECT ORIENTED HOW DO WE BUILD OBJECT ORIENTED SOFTWARE?
12. SOLID
13. SRP SINGLE RESPONSIBILITY PRINCIPLE a class should have a single responsibility
14. OCP OPEN-CLOSED PRINCIPLE software should be open for extension, but closed for modification
15. LSP LISKOV SUBSTITUTION PRINCIPLE subtypes should be useable without affecting the correctness of the software
16. ISP INTERFACE SEGREGATION PRINCIPLE many client-specific interfaces are better than one general-purpose one
17. DIP DEPENDENCY INVERSION PRINCIPLE depend upon abstractions, do not depend upon concretions
18. CQS COMMAND QUERY SEPARATION methods should either modify state or return state, never both.
19. ENCAPSULATION TELL, DON'T ASK PRINCIPLE try to use the query methods as little as possible
20. SOFTWARE HOW DO WE BUILD SOFTWARE NOW?
21. MODEL DB CLIENT user interacts orm persists orm hydrates dto
22. CQRS COMMAND QUERY RESPONSIBILITY SEGREGATION split up your model in separate classes for either returning state or either changing state similar to CQS, but applied to classes design principle
23. WRITE MODEL DB CLIENT command orm persists orm hydrates dto READ MODEL
24. i n t e r f a c e S h o p p i n g C a r t { / / p u b l i c f u n c t i o n _ _ c o n s t r u c t ( $ s h o p p i n g C a r t I d ) ; p u b l i c f u n c t i o n a d d I t e m ( I t e m $ i t e m ) ; p u b l i c f u n c t i o n r e m o v e I t e m ( I t e m $ i t e m ) ; p u b l i c f u n c t i o n c h e c k o u t ( ) ; p u b l i c f u n c t i o n g e t I d ( ) ; p u b l i c f u n c t i o n g e t I t e m s ( ) ; p u b l i c f u n c t i o n g e t T o t a l ( ) ; }
25. i n t e r f a c e S h o p p i n g C a r t R e p o s i t o r y { p u b l i c f u n c t i o n f i n d A l l ( ) ; p u b l i c f u n c t i o n f i n d O n e B y I d ( $ s h o p p i n g C a r t I d ) ; p u b l i c f u n c t i o n s a v e ( S h o p p i n g C a r t $ s h o p p i n g C a r t ) ; }
26. c l a s s S h o p p i n g C a r t A p i C o n t r o l l e r { p u b l i c f u n c t i o n a d d I t e m T o S h o p p i n g C a r t ( $ s h o p p i n g C a r t I d , $ i t e m I d ) { $ s h o p p i n g C a r t = $ t h i s - > s h o p p i n g C a r t R e p o s i t o r y - > f i n d O n B y I d ( $ s h o p p i n g C a r t I d ) ; $ i t e m = $ t h i s - > i t e m R e p o s i t o r y - > f i n d O n e B y I d ( $ i t e m I d ) ; $ s h o p p i n g C a r t - > a d d I t e m ( $ i t e m ) ; $ t h i s - > s h o p p i n g C a r t R e p o s i t o r y - > s a v e ( $ s h o p p i n g C a r t ) ; } p u b l i c f u n c t i o n g e t S h o p p i n g C a r t I n f o ( $ s h o p p i n g C a r t I d ) { $ s h o p p i n g C a r t = $ t h i s - > s h o p p i n g C a r t R e p o s i t o r y - > f i n d O n B y I d ( $ s h o p p i n g C a r t I d ) ; r e t u r n j s o n _ e n c o d e ( ( o b j e c t ) [ ' i d ' = > $ s h o p p i n g C a r t - > g e t I d ( ) , ' n u m b e r O f I t e m s ' = > c o u n t ( $ s h o p p i n g C a r t - > g e t I t e m s ( ) ) , ' t o t a l ' = > $ s h o p p i n g C a r t - > g e t T o t a l ( ) ] ) ; } / / . . . }
27. CQRS SPLIT YOUR MODEL split up your DTOs into read-entities and commands make a separate repository for your read-entities you are able to use your entities for write only you are able to use your read-entities for read only
28. i n t e r f a c e S h o p p i n g C a r t { / / p u b l i c f u n c t i o n _ _ c o n s t r u c t ( $ s h o p p i n g C a r t I d ) ; p u b l i c f u n c t i o n a d d I t e m ( I t e m $ i t e m ) ; p u b l i c f u n c t i o n r e m o v e I t e m ( I t e m $ i t e m ) ; p u b l i c f u n c t i o n c h e c k o u t ( ) ; }
29. i n t e r f a c e S h o p p i n g C a r t R e p o s i t o r y { p u b l i c f u n c t i o n f i n d O n e B y I d ( $ s h o p p i n g C a r t I d ) ; p u b l i c f u n c t i o n s a v e ( S h o p p i n g C a r t $ s h o p p i n g C a r t ) ; }
30. c l a s s A d d I t e m T o S h o p p i n g C a r t i m p l e m e n t s C o m m a n d { p r i v a t e $ s h o p p i n g C a r t I d ; p r i v a t e $ i t e m I d ; p u b l i c f u n c t i o n _ _ c o n s t r u c t ( $ s h o p p i n g C a r t I d , $ i t e m I d ) { $ t h i s - > s h o p p i n g C a r t I d = $ s h o p p i n g C a r t I d ; $ t h i s - > i t e m I d = $ i t e m I d ; } p u b l i c f u n c t i o n g e t S h o p p i n g C a r t I d ( ) { r e t u r n $ t h i s - > s h o p p i n g C a r t I d ; } p u b l i c f u n c t i o n g e t I t e m I d ( ) { r e t u r n $ t h i s - > i t e m I d ; } }
31. COMMANDS message user intention verb, imperative command handler can be refused (ACK-NACK)
32. c l a s s A d d I t e m T o S h o p p i n g C a r t C o m m a n d H a n d l e r i m p l e m e n t s C o m m a n d H a n d l e r { p u b l i c f u n c t i o n h a n d l e ( A d d I t e m T o S h o p p i n g C a r t $ c o m m a n d ) { $ s h o p p i n g C a r t = $ t h i s - > s h o p p i n g C a r t R e p o s i t o r y - > f i n d O n B y I d ( $ c o m m a n d - > g e t S h o p p i n g C a r t I d ( ) ) ; $ i t e m = $ t h i s - > i t e m R e p o s i t o r y - > f i n d O n e B y I d ( $ c o m m a n d - > g e t I t e m I d ( ) ) ; $ s h o p p i n g C a r t - > a d d I t e m ( $ i t e m ) ; $ t h i s - > s h o p p i n g C a r t R e p o s i t o r y - > s a v e ( $ s h o p p i n g C a r t ) ; } / / . . . }
33. COMMANDS explicit user intention task based user interface Ubiquitous language
34. QUERIES read model DTOs read-entities database views
35. i n t e r f a c e S h o p p i n g C a r t I n f o { / / p u b l i c f u n c t i o n _ _ c o n s t r u c t ( $ s h o p p i n g C a r t I d , $ n u m b e r O f I t e m s , $ t o t a l ) ; p u b l i c f u n c t i o n g e t I d ( ) ; p u b l i c f u n c t i o n g e t N u m b e r O f I t e m s ( ) ; p u b l i c f u n c t i o n g e t T o t a l ( ) ; p u b l i c f u n c t i o n j s o n S e r i a l i z e ( ) ; }
36. i n t e r f a c e S h o p p i n g C a r t I n f o R e p o s i t o r y { p u b l i c f u n c t i o n f i n d A l l ( ) ; p u b l i c f u n c t i o n f i n d O n e B y I d ( $ s h o p p i n g C a r t I d ) ; }
37. c l a s s S q l S h o p p i n g C a r t I n f o R e p o s i t o r y i m p l e m e n t s S h o p p i n g C a r t I n f o R e p o s i t o r y { / / . . . p u b l i c f u n c t i o n f i n d O n e B y I d ( $ s h o p p i n g C a r t I d ) { $ s q l = ' S E L E C T . . . ' ; / / s o m e c o m p l e x s q l s t a t e m e n t $ r e s u l t = $ t h i s - > d a t a b a s e - > f e t c h ( $ s q l ) ; r e t u r n n e w S h o p p i n g C a r t I n f o ( $ r e s u l t - > i d , $ r e s u l t - > n u m b e r O f I t e m s , $ r e s u l t - > t o t a l ) ; } }
38. c l a s s S h o p p i n g C a r t A p i C o n t r o l l e r { / / . . . p u b l i c f u n c t i o n g e t S h o p p i n g C a r t I n f o ( $ s h o p p i n g C a r t I d ) { r e t u r n j s o n _ e n c o d e ( $ t h i s - > s h o p p i n g C a r t I n f o R e p o s i t o r y - > f i n d O n B y I d ( $ s h o p p i n g C a r t I d ) ) ; } }
39. c l a s s C o m m a n d A p i C o n t r o l l e r { / / . . . p u b l i c f u n c t i o n h a n d l e ( $ c o m m a n d ) { $ c o m m a n d = $ t h i s - > c o m m a n d D e s e r i a l i z e r - > d e s e r i a l i z e ( $ c o m m a n d ) ; $ t h i s - > c o m m a n d D i s p a t c h e r - > d i s p a t c h ( $ c o m m a n d ) ; } }
40. DESIGN move logic to your model instead of application layer make domain language explicit in your code
41. PROGRAMMER OPTIMIZATION let senior developers work the write side let junior developers work the read side let front-end developers work the client side or not...
42. SOFTWARE HOW DO WE BUILD SOFTWARE NOW?
43. WRITE MODEL DB CLIENT command orm persists sql resultset dto READ MODEL COMMAND HANDLER DTO BUILDER
44. CQRS COMMAND QUERY RESPONSIBILITY SEGREGATION split up your persistence in separate parts for either returning state or either changing state architectural choice
45. WRITE MODEL DB CLIENT command orm persists sql resultset dto READ MODEL COMMAND HANDLER DTO BUILDER DB
46. WRITE MODEL DB CLIENT command orm persists sql resultset dto READ MODEL COMMAND HANDLER DTO BUILDER DB event
47. EVENT message history, a change in the system sentence, passed tense publish-subscribe is the truth
48. c l a s s I t e m W a s A d d e d T o S h o p p i n g C a r t i m p l e m e n t s D o m a i n E v e n t { p r i v a t e $ s h o p p i n g C a r t I d ; p r i v a t e $ i t e m I d ; p r i v a t e $ p r i c e ; p u b l i c f u n c t i o n _ _ c o n s t r u c t ( $ s h o p p i n g C a r t I d , $ i t e m I d , $ p r i c e ) { $ t h i s - > s h o p p i n g C a r t I d = $ s h o p p i n g C a r t I d ; $ t h i s - > i t e m I d = $ i t e m I d ; $ t h i s - > p r i c e = $ p r i c e ; } p u b l i c f u n c t i o n g e t S h o p p i n g C a r t I d ( ) { r e t u r n $ t h i s - > s h o p p i n g C a r t I d ; } p u b l i c f u n c t i o n g e t I t e m I d ( ) { r e t u r n $ t h i s - > i t e m I d ; } p u b l i c f u n c t i o n g e t P r i c e ( ) { r e t u r n $ t h i s - > p r i c e ; } }
49. COMMAND HANDLER turns a command into events uses an aggregate to protect invariants publishes events
50. c l a s s A d d I t e m T o S h o p p i n g C a r t C o m m a n d H a n d l e r i m p l e m e n t s C o m m a n d H a n d l e r { p u b l i c f u n c t i o n h a n d l e ( A d d I t e m T o S h o p p i n g C a r t $ c o m m a n d ) { $ s h o p p i n g C a r t = $ t h i s - > s h o p p i n g C a r t R e p o s i t o r y - > f i n d O n B y I d ( $ c o m m a n d - > g e t S h o p p i n g C a r t I d ( ) ) ; $ i t e m = $ t h i s - > i t e m R e p o s i t o r y - > f i n d O n e B y I d ( $ c o m m a n d - > g e t I t e m I d ( ) ) ; $ s h o p p i n g C a r t - > a d d I t e m ( $ i t e m , $ t h i s - > e v e n t P u b l i s h e r ) ; $ t h i s - > s h o p p i n g C a r t R e p o s i t o r y - > s a v e ( $ s h o p p i n g C a r t ) ; } / / . . . }
51. c l a s s S h o p p i n g C a r t i m p l e m e n t s A g g r e g a t e R o o t { p u b l i c f u n c t i o n a d d I t e m ( I t e m $ i t e m , E v e n t P u b l i s h e r $ e v e n t P u b l i s h e r ) { $ t h i s - > i t e m s [ ] = $ i t e m ; $ e v e n t P u b l i s h e r - > p u b l i s h ( n e w I t e m W a s A d d e d T o S h o p p i n g C a r t ( $ t h i s - > g e t I d ( ) , $ i t e m - > g e t I d ( ) , $ i t e m - > g e t P r i c e ( ) ) ) ; } / / . . . }
52. PROJECTOR turns events into state produces read-models subscribes to events
53. c l a s s S h o p p i n g C a r t I n f o P r o j e c t o r i m p l e m e n t s P r o j e c t o r { p u b l i c f u n c t i o n p r o j e c t ( I t e m W a s A d d e d T o S h o p p i n g C a r t $ e v e n t ) { $ s h o p p i n g C a r t I n f o = $ t h i s - > s h o p p i n g C a r t I n f o R e p o s i t o r y - > f i n d O n B y I d ( $ e v e n t - > g e t S h o p p i n g C a r t I d ( ) ) ; $ s h o p p i n g C a r t I n f o - > u p d a t e ( 1 , $ e v e n t - > g e t P r i c e ( ) ) ; $ t h i s - > s h o p p i n g C a r t I n f o R e p o s i t o r y - > s a v e ( $ s h o p p i n g C a r t I n f o ) ; } / / . . . }
54. PERFORMANCE reading goes faster writing goes slower
55. DESIGN make domain language explicit in your code decouple components
56. READ MODEL READ MODEL WRITE MODEL DB CLIENT command orm persists dto READ MODEL COMMAND HANDLER DTO BUILDER RDB event KVS DDB
57. INFRASTRUCTURE OPTIMIZATION choose other infrastructure that suits better for the problem at hand
58. BTW EVENTSTORMING workshop format to detect commands & events of the business with domain experts introduced by Alberto Brandolini
59. SOFTWARE HOW DO WE BUILD SOFTWARE NOW?
60. READ MODEL READ MODEL WRITE MODEL DB CLIENT command orm persists dto READ MODEL COMMAND HANDLER DTO BUILDER RDB event KVS DDB
61. EVENT SOURCING all events produce the current state all events of an aggregate produce the current state of the aggregate use events as persistence instead of state
62. READ MODEL READ MODEL WRITE MODEL ES CLIENT command event dto READ MODEL COMMAND HANDLER DTO BUILDER RDB event KVS DDB
63. CHANGING STATE an aggregate records its own new events newly recorded events are appended to an event store
64. c l a s s S h o p p i n g C a r t { p u b l i c f u n c t i o n a d d I t e m ( $ i t e m I d , $ p r i c e ) { $ t h i s - > c h a n g e s [ ] = n e w I t e m W a s A d d e d T o S h o p p i n g C a r t ( $ t h i s - > s h o p p i n g C a r t I d , $ i t e m I d , $ p r i c e ) ; } / / . . . }
65. c l a s s A d d I t e m T o S h o p p i n g C a r t C o m m a n d H a n d l e r i m p l e m e n t s C o m m a n d H a n d l e r { p u b l i c f u n c t i o n h a n d l e ( A d d I t e m T o S h o p p i n g C a r t $ c o m m a n d ) { $ s h o p p i n g C a r t = $ t h i s - > s h o p p i n g C a r t R e p o s i t o r y - > f i n d O n B y I d ( $ c o m m a n d - > g e t S h o p p i n g C a r t I d ( ) ) ; $ i t e m = $ t h i s - > i t e m R e p o s i t o r y - > f i n d O n e B y I d ( $ c o m m a n d - > g e t I t e m I d ( ) ) ; $ s h o p p i n g C a r t - > a d d I t e m ( $ i t e m - > g e t I d ( ) , $ i t e m - > g e t P r i c e ( ) ) ; $ t h i s - > e v e n t S t o r e - > c o m m i t ( $ s h o p p i n g C a r t - > g e t C h a n g e s ( ) ) ; } / / . . . }
66. c l a s s E v e n t S t o r e S h o p p i n g C a r t R e p o s i t o r y i m p l e m e n t s S h o p p i n g C a r t R e p o s i t o r y { p u b l i c f u n c t i o n f i n d O n B y I d ( $ s h o p p i n g C a r t I d ) { $ s h o p p i n g C a r t E v e n t s = $ t h i s - > e v e n t S t o r e - > f i n d F o r ( $ s h o p p i n g C a r t I d ) ; r e t u r n S h o p p i n g C a r t : : r e c o n s t i t u t e ( $ s h o p p i n g C a r t I d , $ s h o p p i n g C a r t E v e n t s ) ; } / / . . . }
67. INVARIANTS an aggregate needs history to protect invariants apply all events to the aggregate to rebuild relevant state
68. c l a s s S h o p p i n g C a r t i m p l e m e n t s A g g r e g a t e R o o t { p u b l i c s t a t i c f u n c t i o n r e c o n s t i t u t e ( $ s h o p p i n g C a r t I d , a r r a y $ s h o p p i n g C a r t E v e n t s ) { $ s h o p p i n g C a r t = n e w s e l f ( $ s h o p p i n g C a r t I d ) ; f o r e a c h ( $ s h o p p i n g C a r t E v e n t s a s $ e v e n t ) { $ s h o p p i n g C a r t - > a p p l y ( $ e v e n t ) ; } r e t u r n $ s h o p p i n g C a r t ; } p r i v a t e f u n c t i o n a p p l y ( D o m a i n E v e n t $ e v e n t ) { / / f o r w a r d t o s p e c i f i c a p p l y - m e t h o d } p r i v a t e f u n c t i o n a p p l y I t e m W a s A d d e d T o S h o p p i n g C a r t ( I t e m W a s A d d e d T o S h o p p i n g C a r t $ e v e n t ) { } / / . . . }
69. c l a s s S h o p p i n g C a r t i m p l e m e n t s A g g r e g a t e R o o t { p r i v a t e $ n u m b e r O f I t e m s = 0 ; p u b l i c f u n c t i o n a d d I t e m ( $ i t e m I d , $ p r i c e ) { i f ( $ t h i s - > n u m b e r O f I t e m s > 2 ) { t h r o w n e w E x c e p t i o n ( ' Y o u c a n o n l y h a v e 3 i t e m s i n y o u r s h o p p i n g c a r t ' ) ; } $ e v e n t = n e w I t e m W a s A d d e d T o S h o p p i n g C a r t ( $ t h i s - > s h o p p i n g C a r t I d , $ i t e m I d , $ p r i c e ) ; $ t h i s - > c h a n g e s [ ] = $ e v e n t ; $ t h i s - > a p p l y ( $ e v e n t ) ; } p r i v a t e f u n c t i o n a p p l y I t e m W a s A d d e d T o S h o p p i n g C a r t ( I t e m W a s A d d e d T o S h o p p i n g C a r t $ e v e n t ) { $ t h i s - > n u m b e r O f I t e m s + + ; } }
70. TESTABILITY given a history, when I act upon the system, then something should have changed given certain events, when I issue a command, then events should have happened given a history, how is it represented given certain events, then a certain state should be present
71. c l a s s A d d I t e m T o S h o p p i n g C a r t C o m m a n d H a n d l e r T e s t e x t e n d s T e s t C a s e { / * * @ t e s t * / p u b l i c f u n c t i o n s h o u l d _ r e s u l t _ i n t o _ a n _ I t e m W a s A d d e d T o S h o p p i n g C a r t _ e v e n t ( ) { $ t h i s - > s c e n a r i o - > g i v e n ( n e w S h o p p i n g C a r t W a s C r e a t e d ( / * . . . * / ) ) ; $ t h i s - > s c e n a r i o - > w h e n ( n e w A d d I t e m T o S h o p p i n g C a r t ( / * . . . * / ) ) ; $ t h i s - > s c e n a r i o - > t h e n ( n e w I t e m W a s A d d e d T o S h o p p i n g C a r t ( / * . . . * / ) ) ; } / * * @ t e s t * / p u b l i c f u n c t i o n s h o u l d _ t h r o w _ w h e n _ t r y i n g _ t o _ a d d _ m o r e _ t h e n _ t h r e e _ i t e m s ( ) { $ t h i s - > s c e n a r i o - > g i v e n ( n e w S h o p p i n g C a r t W a s C r e a t e d ( / * . . . * / ) ) ; $ t h i s - > s c e n a r i o - > g i v e n ( n e w I t e m W a s A d d e d T o S h o p p i n g C a r t ( / * . . . * / ) ) ; $ t h i s - > s c e n a r i o - > g i v e n ( n e w I t e m W a s A d d e d T o S h o p p i n g C a r t ( / * . . . * / ) ) ; $ t h i s - > s c e n a r i o - > g i v e n ( n e w I t e m W a s A d d e d T o S h o p p i n g C a r t ( / * . . . * / ) ) ; $ t h i s - > s c e n a r i o - > w h e n ( n e w A d d I t e m T o S h o p p i n g C a r t ( / * . . . * / ) ) ; $ t h i s - > s c e n a r i o - > t h e n ( n e w E x c e p t i o n ( / * . . . * / ) ) ; } p u b l i c f u n c t i o n s e t U p ( ) { $ t h i s - > s c e n a r i o = n e w S c e n a r i o ( / * . . . * / ) ; } p u b l i c f u n c t i o n t e a r D o w n ( ) { $ t h i s - > s c e n a r i o - > v e r i f y ( ) ;
72. } }
73. c l a s s S h o p p i n g C a r t I n f o P r o j e c t o r T e s t e x t e n d s T e s t C a s e { / * * @ t e s t * / p u b l i c f u n c t i o n s h o u l d _ p r o j e c t _ a n _ I t e m W a s A d d e d T o S h o p p i n g C a r t _ e v e n t ( ) { $ t h i s - > s c e n a r i o - > g i v e n ( n e w S h o p p i n g C a r t W a s C r e a t e d ( / * . . . * / ) ) ; $ t h i s - > s c e n a r i o - > g i v e n ( n e w I t e m W a s A d d e d T o S h o p p i n g C a r t ( / * . . . * / ) ) ; $ t h i s - > s c e n a r i o - > t h e n ( n e w S h o p p i n g C a r t I n f o ( / * . . * / ) ) ; } / / . . . }
74. IMMUTABILITY an event store is append only, no database migrations needed messages are immutable, event versioning is needed tests don't need adaptation
75. TEMPORAL QUERIES use read-models to search for certain behaviour over time all history is present
76. CHANGING REQUIREMENTS read-models are temporary, you can throw them away don't change read-models, just make a new one add commands and events as needed
77. SOFTWARE HOW DO WE BUILD SOFTWARE NOW?
78. READ MODEL READ MODEL WRITE MODEL ES CLIENT command event dto READ MODEL COMMAND HANDLER DTO BUILDER RDB event KVS DDB
79. MESSAGES enables messaging enables asynchronous messaging
80. COMMAND BUS receive commands dispatch commands to correct command handler keep track of the command state
81. EVENT QUEUE receive events publish events to correct event listeners
82. READ MODEL READ MODEL WRITE MODEL ES CLIENT command event dto READ MODEL COMMAND HANDLER DTO BUILDER RDB event KVS DDB MQ
83. INFRASTRUCTURE OPTIMIZATION
84. READ MODEL READ MODEL WRITE MODEL ES CLIENT command event query READ MODEL COMMAND HANDLER DTO BUILDER RDB event KVS DDB MQ
85. EVENTUAL CONSISTENCY clients get immediate ACK-NACK projectors receive events asynchronously read-models are not always up to date read-models are always valid
86. SOFTWARE HOW DO WE BUILD SOFTWARE NOW?
87. READ MODEL READ MODEL WRITE MODEL ES CLIENT command event dto READ MODEL COMMAND HANDLER DTO BUILDER RDB event KVS DDB MQ
88. RESPONSIBILITIES
89. WRITE MODEL TURNS A COMMAND INTO EVENTS
90. READ MODEL TURNS EVENTS INTO STATE
91. USER TURNS STATE INTO A COMMAND STATE IS A REPRESENTATION OF EVENTS
92. PROCESS TURNS EVENTS INTO A COMMAND
93. SUMMARY
94. CQRS COMMAND QUERY RESPONSIBILITY SEGREGATION Single Responsiblity Principle applied on class level Single Responsiblity Principle applied on architectural level not an architecture not a framework not a library not event sourcing
95. ES EVENT SOURCING use events as persistence
96. CQRS+ES THEY WORK BETTER TOGETHER
97. BENEFITS components are easy testability programmer optimization infrastructure optimization performance optimization immutability temporal queries changing requirements
98. PITFALLS eventual consistency possible infrastructural chaos boiler plate code immutability
99. QUESTIONS?
100. USEFULL RESOURCES @gregyoung - CQRS guru @ericevans0 - DDD guru @martinfowler - EAA guru @mathiasverraes - DDD & PHP guru @ziobrando - DDD & eventstorming guru @DDDBE - DDD & CQRS gurus DDD/CQRS - https://groups.google.com/forum/#!forum/dddcqrs DDDinPHP - https://groups.google.com/forum/#!forum/dddinphp
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