How to Eat a Whale

You know you need to make changes. Upgrade your software, pull a Humpy Dumpty on the test suite, tame your production emergencies. And yet you never quite get there.

Let's talk through the strategies that are most effective, and how I've succeeded - and often failed - to get to the other side.

Transcript

1. HOW TO EAT A WHALE MAKING THE CHANGES YOU KNOW YOU NEED TO
2. Have you heard of tiny Melinda Mae, Who ate a monstrous whale? She thought she could, She said she would, So she started in right at the tail. - Shel Silverstein
3. not a criticism
4. WE HAVE TO CHANGE
5. ▸ Hard to Maintain ▸ New Features ▸ Better Performance ▸ Security ▸ Ergonomics ▸ Hiring
6. RAILS 5 AS A CASE STUDY
7. it’s a common upgrade
8. ▸ 1.2 ➡ 4.2 ▸ 3.0 ➡ 5.0 ▸ 4.2 ➡ 5.0 ▸ 4.2 ➡ 5.0 success success failure ongoing!
9. this works for other big changes
10. WHY WE DON’T CHANGE
11. the changes are ambiguous
12. the risk is high
13. it’s a lot of work
14. source: git log -L 5,6:Gemfile Date Rails Version Jun ‘19 4.2.11 Aug ‘17 4.2.7.1 Dec ‘16 4.2.7 Mar ‘16 4.1.13 Mar ‘16 4.2.5.2 Feb ‘16 4.2.5.1 Aug ‘15 4.1.13 Jan ‘15 4.1.9 Dec ‘14 4.0.0 … … May ‘13 3.2.8
15. but there is hope!
16. 1. REDUCE AMBIGUITY
17. try to get a list of changes
18. ▸ changelogs ▸ upgrade guide ▸ gem dependency graph ▸ try changes and see what explodes
21. uncover sneaky problems
22. # old class FactoryGirl # new class FactoryBot
23. class Money::Arithmetic def ==(other) # don’t allow comparison w/ non-Money objects unless other.is_a? Money || other.zero? raise ArgumentError end # ... do comparison end end
24. class Money::Arithmetic def ==(other) # warn about problems if other.is_a?(Numeric) && other.nonzero? trigger_warning_and_rollbar end super # run actual comparison end end
25. keep strong test coverage
26. 2. REDUCE RISK
27. take tiny steps
28. ‣ rails 5 ‣ factory_bot ‣ belongs_to ‣ protected_attributes ‣ strong params ‣ activeadmin ‣ devise ‣ upgrade ruby ‣ rails 4.2.11 ‣ sass ‣ coffee ‣ money ‣ etc… ‣ quiet_assets*
29. ‣ factory bot ‣ add shim ‣ use shim for existing cases ‣ upgrade factory girl to most recent version ‣ switch to factory bot and remove shim lots of changes, low risk tiny change, highest risk
31. update code, then dependency
32. FactoryBot.define AtlRollout do # ... end
33. # warning: BigDecimal.new is deprecated; # use BigDecimal() method instead. (BigDecimal.new('-50.00')..BigDecimal.new('50.00')) => 'cold',
34. # in rails 4, this is optional # in rails 5, it’s required belongs_to :packing_facility # this works in both! belongs_to :packing_facility, required: false
35. Make the change easy, Then make the easy change. - Kent Beck
36. surface errors quickly, in the right place
37. NoMethodError: undefined method 'sellout_limit' for nil:NilClass # ./app/models/meal.rb:531:in 'sellout_limit_for' # ./app/models/menu.rb:254:in 'meal_sold_out?' # ./app/models/meal_selection.rb:208:in 'validate_meal_selection'
38. ArgumentError: Couldn’t find 3rd meal for plan 'Standard' in menu ’15-jul-2019' (2 meals for plan) # ./spec/factories/weekly_baskets.rb:131:in `validate_selection!' # ./spec/factories/weekly_baskets.rb:61:in `block (5 levels)’ # ./spec/factories/weekly_baskets.rb:58:in `times' # ./spec/factories/weekly_baskets.rb:58:in `block (4 levels)’
39. 3. REDUCE EFFORT
40. it’s okay to be a bit clever
41. # in rails 4, this is optional # in rails 5, it’s required belongs_to :packing_facility
42. WeeklyBasket.reflect_on_all_associations.each do |association| next if association.macro != :belongs_to foreign_key_field = klass.reflections[association.name.to_s].foreign_key column = klass.columns.find { |c| c.name == foreign_key_field.to_s } required = association.options.fetch(:required, true) && !association.options.fetch(:optional, false) if required && column.null exceptions << sprintf(“%-50s required, but column is nullable", "#{klass}##{association.name}") elsif !required && !column.null exceptions << sprintf("%-50s not required, but column is not nullable", "#{klass}##{association.name}") end end
43. WeeklyBasket.reflect_on_all_associations.each do |association| end next if association.macro != :belongs_to foreign_key_field = klass.reflections[association.name.to_s].foreign_key column = klass.columns.find { |c| c.name == foreign_key_field.to_s } required = association.options.fetch(:required, true) && !association.options.fetch(:optional, false) if required && column.null exceptions << sprintf(“%-50s required, but column is nullable", "#{klass}##{association.name}") elsif !required && !column.null exceptions << sprintf("%-50s not required, but column is not nullable", "#{klass}##{association.name}") end
44. WeeklyBasket#address will be required, but column is nullable WeeklyBasket#meal_plan will be required, but column is nullable WeeklyBasket#shipping_box will be required, but column is nullable WeeklyBasket#shipping_region will be required, but column is nullable
45. namespaces and shims
46. class Money::Arithmetic def ==(other) if other.is_a?(Numeric) && other.nonzero? trigger_warning_and_rollbar end super end end
48. namespace :rails_5 do task check_belongs_to_associations: :environment do silence_warnings do print "Eager Loading..." Rails.application.eager_load! puts “done.” # ... do comparison end end end
49. do the hard work
51. MOVING TARGETS: PEOPLE RISKS
52. it's hard to relearn everything
53. short lived changes (again)
54. make it easier to do the right thing
55. TO SUM THINGS UP
56. ambiguity happens, risk happens, effort happens. but you minimize them
58. THANKS!