Le projet Legacy, quelles stratégies pour s'en sortir ? — Tech.rocks 2019

Transcript

1. What is Legacy Code ? Definition
2. A code you want to change that no one understands but still provides value. Definition
3. A code without predictability Definition
4. A code without predictability Definition Developers have no idea how long a change can take 01.
5. A code without predictability Definition Developers have no idea how long a change can take 01. 02. There is no correlation between the business and the technical complexity
6. A code without predictability Definition Developers have no idea how long a change can take 01. 02. There is no correlation between the business and the technical complexity 03. You don’t know when something will break
7. A code with no test Definition
8. A code with no test Definition « Most of the fear involved in making changes to large code bases is fear of introducing subtle bugs; fear of changing things inadvertently. Without test, you just don’t know whether things are getting better or worse. » — Michael Feathers
9. Hello, I work in the finance industry at Lgo.group. My name is Arnaud LEMAIRE, And my twitter handle is @lilobase Who am I?
10. This talk is focused on strategic considerations and not tactical ones Disclaimer
11. A natural process Why does it appear?
12. A natural process Why does it appear? Add lines of code
13. A natural process Why does it appear? Add lines of code More complexity
14. A natural process Why does it appear? Add lines of code More complexity Increase in software entropy
15. A natural process Why does it appear? Add lines of code More complexity Increase in software entropy Legacy Code
16. You need to let your software die* A natural process that cannot be stopped
17. You need to let your software die* * part of your software 01. A natural process that cannot be stopped
18. You need to let your software die* * part of your software 01. 02. Without bringing the remaining parts with it A natural process that cannot be stopped
19. You need to let your software die* * part of your software 01. 02. Without bringing the remaining parts with it 03. Optimize your software for replacement A natural process that cannot be stopped
20. But that can be slowed down A natural process that cannot be stopped
21. Strategies at the code level Legacy Code
22. Would you rather go to the dentist twice a year or brush your teeth every day? When to refactor
23. When to refactor Always leave the campground cleaner than you found it.
24. Always leave the campground cleaner than you found it. When to refactor This is the « boy scout rule » 01.
25. Always leave the campground cleaner than you found it. When to refactor This is the « boy scout rule » 01. Developing a new feature and refactoring doesn’t mix well! 02.
26. Always leave the campground cleaner than you found it. When to refactor This is the « boy scout rule » 01. 03. When you found a bug, first write a test that triggers it, then fix it. Developing a new feature and refactoring doesn’t mix well! 02.
27. Stop the weekly technical debt repayment session When to refactor
28. Stop the weekly technical debt repayment session When to refactor The « We’ll fix it later » syndrome 01.
29. Stop the weekly technical debt repayment session When to refactor The « We’ll fix it later » syndrome 01. 02. The same cause always produces the same effect
30. Stop the weekly technical debt repayment session When to refactor The « We’ll fix it later » syndrome 01. 02. The same cause always produces the same effect Instead provide a learning time, so you stop writing legacy code 03.
31. Avoid the big bang refactoring
32. The mikado™ method How to refactor
33. The mikado™ method How to refactor Undo when an experiment fail
34. The Hotspot™ method How to refactor
35. The Hotspot™ method How to refactor
36. The Hotspot™ method How to refactor
37. The Hotspot™ method How to refactor
38. Strategies at the system level Legacy system
39. Refactoring ? How to tackle it?
40. Refactoring ? How to tackle it?
41. Refactoring ? How to tackle it?
42. Rewrite ? How to tackle it?
43. Rewrite ? How to tackle it?
44. Ask your business to help you map your (business) domain 01. Invoice Generation Invoicing Car rental
45. Starting from your existing system Don’t start from your existing system
46. Ask them to tag where there is room for improvement. 02. Invoice Generation Invoicing Car rental
47. Select a tagged support service with few dependencies 03. Invoice Generation Invoicing
48. Starting with your core business Don’t start by your core business Invoice Generation Invoicing Car rental
49. Starting with your core business Don’t start by your core business Invoice Generation Invoicing Car rental !
50. Starting with your core business Don’t start by your core business Invoice Generation Invoicing Car rental !
51. Don’t do horizontal slicing ! Don’t do horizontal slicing UI Persistence Service !
52. Don’t do horizontal slicing ! UI Persistence Service Don’t do horizontal slicing
53. Rewrite it… 04. Invoice Generation Invoicing New invoice Generation
54. And put an anti-corruption layer to prevent legacy leakage 05. Invoicing New invoice Generation Legacy API Legacy Database New Api ACL
55. Invoicing New invoice Generation Legacy DB Event bus
56. Invoicing New invoice Generation Legacy DB Event bus Hidden dependencies
57. Invoicing New invoice Generation Legacy DB Event bus
58. Replace the old legacy system 06. Invoicing Invoice Generation New invoice Generation
59. Replace the old legacy system 06. Invoicing New invoice Generation
60. Repeat 07. Invoice Generation Invoicing Car rental
61. Until you can reach the core 08. Invoice Generation Invoicing Car rental
62. The Ship of Theseus strategy also known as the Strangler pattern How to tackle it?
63. The Ship of Theseus strategy also known as the Strangler pattern How to tackle it? You’ll need to coordinate your actions at the system level 01.
64. The Ship of Theseus strategy also known as the Strangler pattern How to tackle it? You’ll need to coordinate your actions at the system level 01. 02. Beware of functional debt
65. The Ship of Theseus strategy also known as the Strangler pattern How to tackle it? You’ll need to coordinate your actions at the system level 01. 02. Beware of functional debt 03. Optimise your new system for replacement!
66. • The Mikado method (Ellnestam & Brolund) • Software Design X-Rays (Thornhill) • Working Effectively with Legacy Code (Feather) • Refactoring (Fowler) Going further Thanks to Michael C. Feather, Adam Thornhill, Cyrille Martraire, Thomas Pierrain, Martin Fowler, Jean-Baptiste Dusseaut, Ola Ellnestam, Daniel Brolund, Adrian Bolboaca
67. Thank you! I work in the finance industry at Lgo.group. My name is Arnaud LEMAIRE, And my twitter handle is @lilobase