Lessons learned from a huge Rails app - RubyConf Brasil 2019

A set of experiences working on a very challenging project, with a domain model constantly evolving, 24/7 availability, multiple teams working in the same codebase, integration with many external services, and so on.
In this talk we'll try go through these experiences, focusing on these questions: How do we approach new features? How do we deal with tech debt or any other risks? What can we do to speed up delivery? Is Rails helping us to achieve our goals? How should be our testing strategy? How do we handle production errors?

Transcript

1. Lessons learned from a huge Rails app Nahuel Garbezza @ngarbezza
2. Olá! Hi! Hola!
3. Who I am!
4. How big is an application? How can we measure it?
5. Ways to measure an application size > ActiveRecord::Base.descendants.size => 557 $ git shortlog -s | wc -l 302
6. Ways to measure an application size > Rails::Engine.subclasses.sum { |e| e.routes.routes.size } => 1554 Bundle complete! 234 Gemfile dependencies, 459 gems now installed.
7. the context
8. Context I worked with
9. “big” means “out of control”
10. but “out of control” is not bad if you trust your team
11. Working together as a group! Building trust in your engineering team
12. what to do with non-Rails code? business logic
13. /lib $ tree lib/ lib/ ├── additional_params.rb ├── address_validator.rb ├── aol_integration.rb ├── api_throttled_client.rb ├── bad_login_detector.rb ├── cache_keys_invalidator.rb ├── command_interpreter.rb ├── customer_survey.rb ├── default_operation.rb ├── html_errors_formatter.rb ├── json_to_xml_to_json.rb ├── log_middleware.rb ├── measure_converter.rb ├── money_helper.rb ├── one_time_activation.rb ├── product_selector.rb ├── profit_calculator.rb ├── registration_step.rb ├── sharing_policy.rb ├── stuff.rb ├── unknown_identity.rb ├── url_generator.rb ├── user_search_result.rb ├── world_changer.rb ├── xml_utilities.rb └── ...
14. modularization
15. what to do with non-Rails code? interfaces entry points Modularization
16. modularization (level 1) namespaces
17. what to do with non-Rails code? api/integrations/facebook Api::Integrations::Facebook Modularization using Namespaces
18. modularization (level 2) Rails engines
19. what to do with non-Rails code? Modularization using Rails engines
20. build a test suite you can trust
21. build a test suite you can trust https://medium.com/@kentbeck_7670/test-desiderata-94150638a4b3
22. “self-growing” tests
23. build a test suite you can trust class Conference < ApplicationRecord has_many :attendants end class Attendant < ApplicationRecord belongs_to :conference end “Self-growing” test: check for factories validity FactoryBot.define do factory :conference do title { 'RubyConfBR 2019' } description { 'foo' } end factory :attendant do name { ‘Nahuel’ } conference end end
24. build a test suite you can trust class FactoriesValidityTest < ActiveSupport::TestCase all_factory_names = FactoryBot.factories.map(&:name) all_factory_names.each do |factory_name| test "factory #{factory_name} creates a valid object" do instance = FactoryBot.build(factory_name) assert_equal true, instance.valid? end end end “Self-growing” test: check for factories validity 1 test running N different instances
25. build a test suite you can trust class Conference < ApplicationRecord has_many :attendants validates :description, length: { minimum: 20 } end class Attendant < ApplicationRecord belongs_to :conference end “Self-growing” test: check for factories validity FactoryBot.define do factory :conference do title { 'RubyConfBR 2019' } description { 'foo' } end factory :attendant do name { ‘Nahuel’ } conference end end Oops
26. build a test suite you can trust class FactoriesValidityTest < ActiveSupport::TestCase all_factory_names = FactoryBot.factories.map(&:name) all_factory_names.each do |factory_name| test "factory #{factory_name} creates a valid object" do instance = FactoryBot.build(factory_name) assert_equal true, instance.valid? end end end “Self-growing” test: check for factories validity Feedback about problems in one of our factories
27. fight against flaky tests ツ
28. build a test suite you can trust Most common flaky tests causes
29. test your tests
30. build a test suite you can trust Mutation Testing expecting the tests to fail https://github.com/mbj/mutant Testing our tests with Mutation Testing
31. taking care of your production errors
32. track notified alerts protocol fix and improve Taking care of production errors
33. Errors give you great feedback Taking care of production errors
34. bonus
36. Muito obrigado! Thank you so much! Muchas gracias!
37. Creative Software Development