Embrace multi-model thinking

Transcript

1. Embrace multi- model thinking! Ivan Nemytchenko, @inem, 2019

2. • Freelancing • Exploring apps architecture • Writing book •

   Teaching at Goodprogrammer.ru • Gitlabbing • Travelling Ivan Nemytchenko Omsk → Belgrade @inem http://inem.at

3. Rubytrip! 40 days, 4 conferences, 8 countries - RubyConfBY Minsk

   - April 6 - RubyDay Verona - April 11 - RubyWine Kishinev - April 13 - RailsConf Minneapolis - April 30 - Saint P RubyConf - June 1-2

4. Rubytrip! 40 days, 4 conferences, 8 countries - RubyConfBY Minsk

   - April 6 - RubyDay Verona - April 11 - RubyWine Kishinev - April 13 - RailsConf Minneapolis - April 30 - Saint P RubyConf - June 1-2

5. 1.System thinking 2.State 3.Layers of abstractions 4.Side-effects 5.Entry point pressure

   6.Building blocks

6. 1.System thinking 2.State 3.Layers of abstractions 4.Side-effects 5.Entry point pressure

   6.Building blocks

7. System thinking Lifecycle Roles ISO/IEC/ IEEE 42010 Systems and software

   engineering — Architecture description coursera.org/learn/system-thinking

8. : Roles System thinking

9. None
10. None
11. None
12. None
13. None
14. None
15. None
16. None
17. None
18. None
19. None

20. Architect role

21. Number of models 25 50 75+

22. Inception → Growth → Operation → (Decay) System thinking: Lifecycle

23. Design Stamina Hypothesis by Martin Fowler

24. Inception → Growth → Operation → (Decay)

25. Inception → Growth → Operation → (Decay)

26. Inception → Growth → Operation → (Decay)

27. Inception → Growth → Operation → (Decay)

28. State

29. 1.Invited 2.Registered 6.Deleted 3.Banned 5.Expired 4.Promoted User

30. 1.Invited 2.Registered 6.Deleted 3.Banned 5.Expired 4.Promoted User Invoice 1.Created 2.Sent

    3.Delivered 4.Paid 5.Expired Task 1.Created 2.Assigned 3.Sheduled 4.Completed 5.Archived

31. The natural way to implement states

32. - if current_organisation_subscribed? %p You are currently subscribed, using the

    following payment method: %p== #{@org.card_brand}: **** **** **** #{@org.card_last4} %p== Expires #{@org.card_exp_month} / #{@org.card_exp_year} - if @org.last_charge %p== The last payment of $#{@org.last_charge.amount/100} was taken on #{@org.last_charge.created_at.strftime("%d %b % %p== The next payment of $100 is due to be taken on #{(@org.last_charge.created_at + 1.month).strftime("%d %b %Y")} = link_to "Update credit card", edit_subscription_path, class: "btn btn-primary" %p = link_to "Cancel my subscription", subscription_path, method: "DELETE", class: "btn btn-danger", data: {confirm: 'Ar sure?'} - else - if @org.trial_ended? %h2 Thank you for trialing our product %h4 To continue using our product please subscribe to the following plan: - else %h2== Thank you for trialing our product (#{distance_of_time_in_words(@org.created_at, Time.zone.now)} left) %h4 To continue using our product after trial please subscribe to the following plan: %p $100/month %p Up to 500 devices and 200 users %p 3 admin users %p CSV/XLS upload = link_to "Subscribe", new_subscription_path, class: 'btn btn-primary'

33. - if current_organisation_subscribed? #... - if @org.last_charge #... - elsif

    @org.last_charge_status != 'success' #... #... - if @org.expires_at #... - else - if @org.trial_ended? #... - else #... #...

34. if current_user.active && current_user.account && !current_user.account.deleted && current_org.trial_ends_at > Time.current

35. Every flag doubles the number of states .trial_ended? .expired? .cancelled?

    .subscription_expired? 4 flags = 16 states!

36. Flags can be hidden dates ranges, associations, status fields -

    if current_organisation_subscribed? #... - if @org.last_charge #... - elsif @org.last_charge_status != 'success' #... #... - if @org.expires_at #... - else - if @org.trial_ended? #... - else #... #...

37. State Machines

38. State Machines

39. State Machines

40. State Machines

41. gem ‘aasm’ gem ‘state-machines’

42. state_machine :state, initial: :trial do state :trial state :trial_ended state

    :subscribed state :cancelled_subscription state :not_subscribed state :payment_error event :subscribe do transition [:trial, :not_subscribed, :trial_ended] => :subscribed end event :disable_trial do transition :trial => :trial_ended end event :usage_period_ended do transition :cancelled_subscription => :not_subscribed end #... end

43. - if current_org.trial? #... - elsif current_org.trial_ended? #... - elsif

    current_org.subscribed? #... - elsif current_org.cancelled_subscription? #... - elsif current_org.payment_error? #... - elsif current_org.not_subscribed? #... render partial: current_org.state

44. def something(org) if org.new_record? # ... 16*2 = 32 states!

45. Control the number of degrees of freedom of your app

46. Entry point pressure

47. None
48. None
49. None

50. False assumtions 1 model → 1 controller respond_to

51. None
52. None
53. None
54. None

55. Small scale respond_to do |format| format.html { render locals: {query:

    params[:q]} } format.json { @devices = @devices.first(5) @employees = @employees.first(3) } end

56. larger scale (REDMINE) respond_to do |format| format.html { @issue_count =

    @query.issue_count @issue_pages = Paginator.new @issue_count, per_page_option, params['page'] @issues = @query.issues(:offset => @issue_pages.offset, :limit => @issue_pages.per_page) render :layout => !request.xhr? } format.api { @offset, @limit = api_offset_and_limit @query.column_names = %w(author) @issue_count = @query.issue_count @issues = @query.issues(:offset => @offset, :limit => @limit) Issue.load_visible_relations(@issues) if include_in_api_response?('relations') } format.atom { @issues = @query.issues(:limit => Setting.feeds_limit.to_i) render_feed(@issues, :title => "#{@project || Setting.app_title}: #{l(:label_issue_plural)}") } format.csv { @issues = @query.issues(:limit => Setting.issues_export_limit.to_i) send_data(query_to_csv(@issues, @query, params[:csv]), :type => 'text/csv; header=present', :filename => 'issues.csv') } format.pdf { @issues = @query.issues(:limit => Setting.issues_export_limit.to_i) send_file_headers! :type => 'application/pdf', :filename => 'issues.pdf' } end

57. HTML, JSON, PDF, RSS they all used in different ways

    different subsets of data different ways to generate results So it makes sense to create separate REST representations

58. TOP-LEVEL namespaces class Web::ArticlesController < Web::ApplicationController #... end class Api::ArticlesController

    < Api::ApplicationController #... end

59. Hierarchy based on “BOUNDED CONTEXTS” scope module: :web do namespace

    :moderation do resources :articles, only: [:index, :edit, :update, :show] do member do patch :publish end end end resources :articles do member do patch :moderate end scope module: :articles do resources :comments do scope module: :comments do resources :likes, only: [:create] end end end end root 'welcome#index' end

60. Reduce entry point pressure

61. railshurts.com/lifecycle Rails developer Lifecycle

62. Rails developer Lifecycle railshurts.com/lifecycle

63. railshurts.com/lifecycle Rails developer Lifecycle

64. Painless Rails principles 1.Differentiate 'schema' from 'implementation' 2.Reduce entry point

    pressure 3.Control the number of degrees of freedom of the app 4.Don't mix layers of abstractions 5.Don't fight against the framework railshurts.com/rails-principles

65. Sources SICP (Structure and Interpretation of Computer Programs) TAPL (Types

    and Programming Languages) by Benjamin C. Pierce DDD (Domain-driven design) by Eric J. Evans CC2e (Code Complete 2nd edition) by Steve McConnell railshurts.com/rails-principles ISO/IEC/ IEEE 42010 Systems and software engineering — Architecture description

66. Email mini-course “Rails Pitfalls”: railshurts.com/rails-pitfalls inem.at, @inem