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
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
50. False assumtions 1 model → 1 controller respond_to
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