I've Made a Huge Mistake - GoRuCo 2018

How we got services wrong and what we learned along the way

Transcript

1. I’ve Made a Huge Mistake
   How we got services wrong and what we learned along the way
   Kelly Sutton — GoRuCo 2018
   

   View Slide

2. Overview
   I. About Me
   
   II. Breaking the Monolith
   
   III. 5 Sweet Tips
   
   IV. Wrap Up
   

   View Slide

3. Part I:
   
   About Me
   

   View Slide

4. About Me
   

   View Slide

5. About Greta
   

   View Slide

6. About Greta
   

   View Slide

7. About Greta
   

   View Slide

8. About Greta
   

   View Slide

9. But that’s not why we’re here
   

   View Slide

10. We’re here to talk about Rails
    projects that push the limits
    

    View Slide

11. View Slide

12. Time Geography
    Money People
    

    View Slide

13. Correctness > Performance
    

    View Slide

14. So let’s talk about how things go
    wrong, and when things get too big
    

    View Slide

15. Part II:
    
    Breaking the Monolith
    

    View Slide

16. The Swamp
    

    View Slide

17. View Slide

18. View Slide

19. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

20. “Let’s Extract a Service!”
    

    View Slide

21. Photo by Thomas Halfmann
    

    View Slide

22. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

23. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

24. The Swamp
    Payroll
    HR
    Benefits
    Infra
    HR v2
    

    View Slide

25. The Swamp
    Payroll
    HR
    Benefits
    Infra
    HR v2
    

    View Slide

26. The Swamp
    Payroll
    Old HR
    Benefits
    Infra
    HR v2
    

    View Slide

27. But there is a better way
    

    View Slide

28. View Slide

29. Applications vs. Services
    

    View Slide

30. View Slide

31. Applications vs. Services
    

    View Slide

32. Applications vs. Services
    Have their own process Might have their own process
    

    View Slide

33. Applications vs. Services
    Have their own process Might have their own process
    Have their own database Probably share a database
    

    View Slide

34. Applications vs. Services
    Have their own process Might have their own process
    Have their own database Probably share a database
    Scale independently Scales with the host app
    

    View Slide

35. Applications vs. Services
    Have their own process Might have their own process
    Have their own database Probably share a database
    Scale independently Scales with the host app
    Might be an another language Share the same language
    

    View Slide

36. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

37. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

38. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

39. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

40. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

41. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

42. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

43. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

44. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

45. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

46. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

47. The Swamp
    Payroll
    HR
    Benefits
    Infra
    

    View Slide

48. Conceptual
    Compression
    

    View Slide

49. View Slide

50. Conceptual
    Expansion
    

    View Slide

51. Part III:
    
    5 Sweet Tips
    

    View Slide

52. Recommendation #1
    
    Mind and Avoid Circular
    Dependencies
    

    View Slide

53. As your Rails code base grows,
    question bidirectional relationships
    

    View Slide

54. 1 # app/models/company.rb
    2 class Company < ApplicationRecord
    3 has_many :employees
    4 end
    5
    6 # app/models/employee.rb
    7 class Employee < ApplicationRecord
    8 belongs_to :company
    9 end
    

    View Slide

55. 1 # app/models/company.rb
    2 class Company < ApplicationRecord
    3 has_many :employees
    4 end
    5
    6 # app/models/employee.rb
    7 class Employee < ApplicationRecord
    8 belongs_to :company
    9 end
    Do we need this?
    

    View Slide

56. Company Employee
    

    View Slide

57. Company Employee
    

    View Slide

58. Recommendation #2
    
    Use Value Objects to
    Traverse Edges
    

    View Slide

59. 1 # app/services/company_signed_up.rb
    2 class CompanySignedUp
    3 def self.call(company)
    4 CompanyMailer.welcome_email(company)
    5 StatsTracker.company_signed_up(company)
    6 end
    7 end
    

    View Slide

60. 1 # app/services/company_signed_up.rb
    2 class CompanySignedUp
    3 def self.call(company)
    4 user_first_name = company.admin_first_name
    5 email = company.admin_email
    6
    7 CompanyMailer.welcome_email(email, user_first_name)
    8 StatsTracker.company_signed_up(company.id)
    9 end
    10 end
    

    View Slide

61. Recommendation #3
    
    Avoid Callbacks
    

    View Slide

62. 1 # app/models/company.rb
    2 class Company < ApplicationRecord
    3 after_create :send_update_email, if: :has_email?
    4
    5 private
    6
    7 def send_update_email
    8 CompanyMailer.welcome_email(self)
    9 end
    10 end
    

    View Slide

63. Company CompanyMailer
    

    View Slide

64. 1 # app/services/create_company.rb
    2 class CreateCompany
    3 def self.call(company_params)
    4 company = Company.create!(company_params)
    5
    6 CompanyMailer.welcome_email(company)
    7 end
    8 end
    

    View Slide

65. Company CompanyMailer
    CreateCompany
    

    View Slide

66. Recommendation #4
    
    Extract Services first,
    then extract Applications
    

    View Slide

67. Recommendation #5
    
    Move slowly!
    

    View Slide

68. Part IV:
    
    Wrap Up
    

    View Slide

69. –Kent Beck
    “Make the hard change easy
    (this may be hard),
    then make the easy change.”
    

    View Slide

70. Thanks!
    Slides and more available at kellysutton.com
    

    View Slide

71. References
    • Bernhardt, Gary. “Boundaries.” 2012.
    
    • Bernhardt, Gary. “Functional Core, Imperative Shell.” 2012.
    
    • Evans, Eric. “Domain-Driven Design: Tackling Complexity in the Heart of Software.” 2003.
    
    • Fowler, Martin, et al. “Refactoring: Improving the Design of Existing Code.” 1999.
    
    • Feathers, Michael. “Working Effectively with Legacy Code.” 2004.
    
    • Hickey, Rich. “Simple Made Easy.” 2011.
    
    • Scott, James C. “Seeing Like a State.” 1999.
    
    • Searls, Justin. “My Preferred Method of TDD.” 2017
    
    • Spolsky, Joel. “Things You Should Never Do, Part I.” 2006.
    

    View Slide

72. Special Thanks
    • Noa Elad
    
    • Matan Zruya
    
    • Sihui Huang
    
    • Natalie Wong
    
    • Karlo Hoa
    
    • Amelie Meyer-Robinson
    
    • Quentin Balin
    

    View Slide