Arquitecturas basadas en eventos tales como Event Sourcing tienen múltiples beneficios: escalabilidad, gestión de la complejidad, auditoría, etc. Pero llegar a ellas es duro. Nos faltan conocimientos, experiencia y coraje. En esta charla, mostraré algunos trucos y consejos para evolucionar vuestra arquitectura actual hacia Event Sourcing paso a paso. Empezaremos desde una aplicación con arquitectura hexagonal y acabaremos a las puertas de Event Sourcing.

1. De Arquitectura Hexagonal
a Event Sourcing
Carlos Buenosvinos (@buenosvinos)
Bilbostack, 26 de Enero, 2019
Bilbao

3. Carlos Buenosvinos
@buenosvinos
3
VP Technology @ XING
Consultor y Formador como Hobby
+10 años como CTO, VPs, Director
Equipos de hasta 100 personas
E-Commerce, E-Learning,
Payments, Classifieds, Recruiting
Atrápalo (500M EUR),
PCComponentes (300M EUR)

4. Domain-Driven
Design in PHP
Carlos Buenosvinos, Christian Soronellas and Keyvan Akbary
https://leanpub.com/ddd-in-php

5. Ansistrano
https://ansistrano.com
5

6. @buenosvinos
6

8. Barcelona Valencia
Remote
https://corporate.xing.com/en/career/jobs/

9. a Company
9
evolving its architecture.

11. Buenosvinos
Maturity Model
Level 1: Spaghetti
Level 2: Framework Fanboy
Level 3: Hexagonal Architecture
Level 4: Hex. + Domain Events
Level 5: Stepping Stone (CQRS)
Level 6: Event Sourcing + CQRS
11

12. Buenosvinos
Maturity Model
Level 1: Spaghetti
Level 2: Framework Fanboy
Level 3: Hexagonal Architecture
Level 4: Hex. + Domain Events
Level 5: Stepping Stone (CQRS)
Level 6: Event Sourcing + CQRS
12

13. I want to tell
1
3
you a real story about…

14. a Company
1
4
evolving its architecture.

15. I don’t rewrite
Apps from
Scratch 15

18. Level 1:
Spaghetti Architecture
• Multiple Application Entry Points
- create_user.php, delete_user.php, …
• Infrastructure and Domain Together
- PHP and SQL within HTML
• Lack of Testing
• Difficult to Maintain
1
8

19. New App Old App
Matching by
URL
Moving Away:
Middleware Approach
https://carlosbuenosvinos.com/migrating-progressively-to-symfony-without-pain-with-stackphp/

20. Level 2:
Layered Architecture /
Framework Fanboy Architecture
• Single Application Entry Point
- app.php
• Some structure is present (MVC)
• Still Mixing Infrastructure and Domain
- Long Controllers with SQL and
Business Logic, Dummy Entities
(getters and setters)
• No testing or using Web Framework
• Difficult to upgrade Infrastructure
Components
2
0

28. Moving to
Hexagonal Architecture
• Pick an action in the Web Controller
- Coloring Exercise: Identify Infrastructure
references (ORM, HTTP Rest Calls, Caching,
etc.)
- Extract Variable and to the top
• Extract Business Logic into Application Services
(Copy and Paste)
• Move Infrastructure references away
- Interfaces Infrastructure and the Rest
- Database Tx can be move to Repositories
• Start Unit Testing from Application Services
28

32. Benefits of
Hexagonal Architecture
• Separation of Concerns
• Decoupled from the Framework
• Delays Infrastructure Decisions
- Persistence Storage or Delivery
Mechanism (Web, API, CLI, etc.)
• Easy to Test
- Testing Application Services (or CH)
- Testing Entities
- Mocking between the boundaries
32

33. https://carlosbuenosvinos.com/rigor-talks-php-13-refactor-use-case-i-spanish/
https://carlosbuenosvinos.com/rigor-talks-php-14-refactor-use-case-ii-spanish/
https://carlosbuenosvinos.com/rigor-talks-php-15-refactor-use-case-iii-spanish/
https://carlosbuenosvinos.com/rigor-talks-php-16-refactor-use-case-iv-spanish/
https://carlosbuenosvinos.com/rigor-talks-php-17-refactor-use-case-v-spanish/
https://carlosbuenosvinos.com/rigor-talks-php-18-tell-dont-ask-spanish/
https://carlosbuenosvinos.com/rigor-talks-php-19-refactor-use-case-vi-spanish/

34. New Tech Policies in the Team:
1. Everything New: Hexagonal Architecture
2. Touching an Old Feature: Boy Scout Rule ("Always leave
the campground cleaner than you found it.”)
3. 100% Coverage in the Application Services
34

35. Coverage
going up!
35

36. Buenosvinos
Maturity Model
Level 1: Spaghetti
Level 2: Framework Fanboy
Level 3: Hexagonal Architecture
Level 4: Hex. + Domain Events
Level 5: Stepping Stone (CQRS)
Level 6: Event Sourcing + CQRS
36

37. At this point,
37
you can be consultant too!

38. “… and I want to
notify the user by
email, logging and
sending a BI tracking”
Company’s Product Owner
38

39. 2
2

40. Team starts to
face new issues
• # of Dependencies Grows
• Application Service complexity Grows
• More Chances to Introduce Bugs
- More developers touching the same
file (Main Task and Subtasks mixed)
• More Subtasks in the same feature,
Worse Performance!!
40

41. Domain Events
41
to the rescue!

42. Domain Event
Example
42

43. Firing a Domain
Event
43

44. Domain Event
Publisher
Example
44

45. Domain Event
Listener
(Elastic Example)
45

47. Domain Event
Listener
(MySQL Example)
47

48. Domain Event
Listener
(Rabbit Example)
48

49. Registering
Domain Event
Listeners
49

50. Sync all the
things!
50

51. TechPoliciesAdded (ok, it’s a bad joke!)
1. Subtasks of a Feature are developed in a different
Application Service and attached via Listener
2. Fire any new Event that Business may be interested
3. Let’s have a TV screen to monitor realtime Business
metrics to be proactive.
51

52. Composition by
Domain Events
52

53. Buenosvinos
Maturity Model
Level 1: Spaghetti
Level 2: Framework Fanboy
Level 3: Hexagonal Architecture
Level 4: Hex. + Domain Events
Level 5: Stepping Stone (CQRS)
Level 6: Event Sourcing + CQRS
53

54. “Hey team! Have you
realised that the item
page is getting quite
slow?”
Company’s Product Owner
54

55. Perfomance!
55
Multiple Costly Requests
(#, external, joins, etc.)

56. Async all the
things!
56

57. 57

58. Restaurant
Page 1 Query
Redis o
Elastic
WorkerDomain
Event
Command
(Application
Service)
QUERY
COMMAND
RESPONSIBILITY SEGREGATION (CQRS)

60. NOT PROPER CQRS

61. Problem #1:
2 Infras / 1 Tx
61

62. What strategies to deal with these
inconsistencies can we follow?
• Let inconsistencies happen
- The Command Handler will manage
itself (firing ArticleWasAdded, sent to
RabbitMQ, but failed Database Tx)
- Feasible for most operational tasks
(sending email, non-critical tracking,
etc.)
• New Article Added Action and its Event
persisted in the same Tx. Then Worker
to move Events to Rabbit.
• Global TX (Noooooooooo!)
62

63. Problem #2:
Diff(ORM) !== Diff(Events)
63

66. Max
Performance!
66

67. Buenosvinos
Maturity Model
Level 1: Spaghetti
Level 2: Framework Fanboy
Level 3: Hexagonal Architecture
Level 4: Hex. + Domain Events
Level 5: Stepping Stone (CQRS)
Level 6: Event Sourcing + CQRS
* Tested with just 20 companies aprox.
67

69. Buenosvinos
Maturity Model
Level 1: Spaghetti
Level 2: Framework Fanboy
Level 3: Hexagonal Architecture
Level 4: Hex. + Domain Events
Level 5: Stepping Stone (CQRS)
Level 6: Event Sourcing + CQRS
69

70. Moving to Event Sourcing
• Every Entity is reconstituted from
Events
• Benefits:
• Historical Logs of our Entities
• Audit Environments
• Realtime processing
• Reproduce environments up to
specific state
70

72. Our Main Database is nothing
but a Cache (Can we get rid
of it? How much does it
cost?)
72

76. Buenosvinos
Maturity Model
Level 1: Spaghetti
Level 2: Framework Fanboy
Level 3: Hexagonal Architecture
Level 4: Hex. + Domain Events
Level 5: Stepping Stone (CQRS)
Level 6: Event Sourcing + CQRS
76

78. @buenosvinos
7
8

79. Thank you
for your attention.