Surrounded by Microservices

The slides for the 'Surrounded by Microservices' talk , Euruko 2019, Rotterdam.

Transcript

1. Surrounded by
   Microservices
   

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2. The DVD Rental Company
   

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3. Video on demand
   

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4. Original content
   

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5. Big Shift?
   

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6. Old industry
   !
   

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7. Remember these?
   

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8. Problem space
   !
   

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9. Studio apps
   

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10. Starting with a monolith
    

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11. Specialization
    !
    

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12. Starting fresh
    !
    

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13. Ruby On Rails
    !
    

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14. The Active Record Pattern
    !
    Domain Objects
    "
    Business Rules
    #
    Validations
    $
    Persistence
    

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15. Distributed data
    !
    

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16. Various data sources
    !
    REST API
    "
    JSON API
    #
    GRPC
    $
    GraphQL
    %
    Local Database
    

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17. "Data that lives in our database today
    might live in a service tomorrow"
    

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18. Architecture that clearly separates
    the business logic from any kind of
    implementation details and protocols
    

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19. Hexagonal
    Architecture
    

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21. Core concepts
    

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22. Entities
    

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23. The repositories
    

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24. The data sources
    

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25. Interactors
    

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26. Implementing
    business logic
    

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27. Entities
    module Workflows
    class ProductionEntity < BaseEntity
    attribute :id, AttrType::Strict::Integer
    attribute :title, AttrType::Strict::String
    attribute :logline, AttrType::Strict::String.optional
    end
    end
    

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28. dry-struct
    

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29. Entities
    class ProductionEntity < BaseEntity
    attribute :id, AttrType::Strict::Integer
    attribute :title, AttrType::Strict::String
    attribute :logline, AttrType::Strict::String.optional
    end
    

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30. Repositories (Custom DSL)
    class ProductionRepo < BaseRepo
    entity_class ProductionEntity
    def initialize(data_source: MovieProduction)
    super
    end
    def find_by_id(id)
    wrap(data_source.find_by_id(id))
    end
    def search_by_title(title)
    wrap(data_source.search_by_title(title))
    end
    end
    

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31. Data Sources
    class MovieProduction < ApplicationRecord
    def self.search_by_title(title)
    where('title LIKE ?', "#{sanitize_sql_like(title)}%") }
    end
    end
    

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32. Data Sources
    class MovieProductionAPI
    def self.search_by_title(title)
    SwaggerClient::MovieProductionsApi.advanced_search(
    search_param: title,
    headers: { ... },
    ...
    )
    end
    end
    

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33. Data Source Independent
    # using the default data source
    repo = ProductionRepo.new
    # swapping for a REST API data source
    repo = ProductionRepo.new(data_source: MovieProductionAPI)
    

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34. Interactor gem
    

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35. Interactors
    module Workflows
    class OnboardProduction
    include NetflixInteractor
    def self.call(production_id:, vertical_id:, repo: ProductionRepo.new)
    super
    end
    def call
    # validate inputs
    # is it okay to onboard a production?
    # cover edge cases
    # notify others about a production being onboarded
    end
    end
    end
    

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36. Hanami
    

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37. Implementing
    data sources
    

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38. API Clients
    

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39. Handwritten API Clients
    

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40. Autogenerated API Clients
    

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41. Autogenerated API Clients
    Swagger Code Generator
    GRPC
    JSON API Spec
    

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42. Dealing with
    errors
    

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43. The network is unreliable
    

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44. Graceful failure
    

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45. Logging downstream requests
    

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46. Metrics
    

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47. Error reporting
    

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48. Errors Must Be Actionable
    

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49. Avoid Alarm Fatigue
    

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50. Setting up thresholds
    

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51. Going straight
    to the data
    source
    

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52. Does it scale?
    

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53. Eventual consistency
    

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54. Consistency vs availability
    

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55. "Services should respond in a timely
    manner"
    

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56. What's in the future?
    

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57. Delaying
    decisions
    

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58. Project paradox
    

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59. The purpose of a good architecture is to delay decisions.
    Why? Because when we delay a decision, we have more
    information when it comes time to make it.
    - Uncle Bob
    

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60. Postgres? Cassandra? Redis?
    Elasticsearch?
    

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61. Testing
    Strategy
    

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62. The test suite must be reliable and fast
    

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63. Rails Testing
    

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64. Testing business logic
    

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65. Dependency Injection
    

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66. Testing with verified doubles
    describe Workflows::OnboardProduction do
    let(:production_id) { SecureRandom.uuid }
    let(:vertical_id) { SecureRandom.uuid }
    let(:response) do
    described_class.call(production_id: production_id, vertical_id: vertical_id, repo: repo)
    end
    describe 'when a production already exists' do
    let(:repo) { instance_double(Workflow::ProductionRepo, find_by_id: existing_production) }
    it 'the response is a failure' do
    expect(response).to be_a_failure
    end
    end
    ...
    end
    

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67. Integration specs
    data sources & end to end
    

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68. A fast and reliable spec
    suite
    Finished in 1 minute 2.35 seconds (files took 2.93 seconds to load)
    2015 examples, 0 failures
    

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69. Conclusion
    

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70. Separate business
    logic from
    implementation
    details
    

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71. Delay decisions
    

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72. Damir Svrtan
    Twitter: @DamirSvrtan
    

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