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A Journey from Hexagonal Architecture to Event Sourcing
This document summarizes a company's evolution from a "spaghetti" architecture to using event sourcing. It describes how the company moved to hexagonal architecture and incorporated domain events to address growing complexity. As issues with performance and consistency arose, the document suggests preparing for event sourcing, where entities are loaded from stored events and the database acts as a cache. The overall maturity model progresses from initial architectures to full event sourcing and CQRS.
A Journey from Hexagonal Architecture to Event Sourcing
- 1. A Journey from HexagonalArchitecture to Event Sourcing Carlos Buenosvinos (@buenosvinos) Polycon, October 6th, 2017 Barcelona
- 2. 2 Who am I? CarlosBuenosvinos • Technical Director @ XING • Consultant • +10 years on Tech Leadership (CTO, VP of Engineering, Director) • Teams up to 100 people • E-Commerce, E-Learning, Payments, Classifieds, Recruiting • Atrápalo (500M EUR), PCComponentes (300M EUR)
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- 4. 4 Domain-Driven Design in PHPBook Carlos Buenosvinos, Christian Soronellas and Keyvan Akbary https://leanpub.com/ddd-in-php
- 5. I want totell you a real story about… 5
- 6. a Company evolving itsarchitecture. 6
- 7. Spaghetti Architecture 7 • Multiple ApplicationEntry Points - create_user.php, delete_user.php, … • Infrastructure and Domain Together - PHP and SQL within HTML • Lack of Testing • Difficult to Maintain
- 8. Framework Fanboy Architecture 8 • SingleApplication 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
- 9. 9 Application Service Any Random Action ina Web Controller
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- 11. Buenosvinos Maturity Model 11 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.
- 12. Buenosvinos Maturity Model 12 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.
- 13. Benefits of Hexagonal Architecture 13 •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
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- 16. Moving to Hexagonal Architecture 16 •Pick an action in the Web Controller - 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 - ORM flush() into Repositories • Start Unit Testing from Application Services
- 17. New Tech Policiesin 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 17
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- 19. Buenosvinos Maturity Model 19 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.
- 20. At this point, youcan be consultant too! 20
- 21. 21 “… and Iwant to notify the user by email, logging and sending a BI tracking” Company’s Product Owner
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- 23. Team starts to facenew issues 23 • # 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!!
- 24. Domain Events to therescue! 24
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- 34. TechPoliciesAdded (ok, it’sa 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. 34
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- 36. Buenosvinos Maturity Model 36 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.
- 37. 37 “Hey team! Haveyou realised that the item page is getting quite slow?” Company’s Product Owner
- 38. Perfomance! Multiple Costly Requests (#,external, joins, etc.) 38
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- 41. Have you eversent an email about something that didn’t finally happen? 41
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- 45. Problem #1: 2 Infras/ 1 Tx 45
- 46. What strategies todeal with these inconsistencies can we follow? 46 • 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!)
- 47. Problem #2: Diff(ORM) !==Diff(Events) 47
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- 50. Buenosvinos Maturity Model 50 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.
- 52. Buenosvinos Maturity Model 52 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.
- 53. What should benext? Getting Ready for Event Sourcing 53 • Entities are loaded from the Events already Stored • Our Main Database is nothing but a Cache (Can we get rid of it? How much does it cost?) • Watch Marco Pivetta’s Presentation and/or attend his Workshop on Sunday.
- 54. Thank you for yourattention.