Introduction au DDD sous l’angle stratégique — hyf mai 2020

Le DDD, est une approche de la conception logicielle dirigée par le domaine, fondée sur deux principes :

- les conceptions complexes doivent être basées sur un modèle
- l’accent doit être sur le domaine et la logique associée

Dans cette présentation nous nous intéressons à la partie essentielle, mais souvent oubliée du DDD : les patterns stratégiques.

Transcript

1. www.lilobase.me
   The strategies
   behind DDD
   @lilobase
   #MeetupDeconfinement
   lgo.group
   

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2. Let’s start a new project !
   

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3. Let’s start a new project !
   We just receive the
   customer’s requirements,
   we still need to clarify a few
   things.
   But you can start the
   preliminary design phase !
   Let's do a sprint zero !
   

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4. SQL or NoSQL ?
   Java or C# ?
   Spring Boot or
   Quarkus ?
   PostgreSQL or
   MySQL ?
   Kafka or Redis ?
   Microservices or
   Monolith ?
   Kubernetes or
   Nomad ?
   Angular or
   React ?
   

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5. What are you working on ?
   There are still some
   uncertainties, but we’re
   gonna use kafka
   …
   

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6. Java or C# ? PostgreSQL or
   MySQL ?
   Kafka or Redis ?
   Microservices or
   Monolith ?
   Kubernetes or
   Nomad ?
   SQL or NoSQL ?
   Spring Boot or
   Quarkus ?
   These issues address
   only the solution
   

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7. Java or C# ? PostgreSQL or
   MySQL ?
   Kafka or Redis ?
   Microservices or
   Monolith ?
   Kubernetes or
   Nomad ?
   SQL or NoSQL ?
   Spring Boot or
   Quarkus ?
   These issues address
   only the solution
   But not the problem
   What should we do ?
   

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8. These issues address
   only the solution
   But not the problem
   What should we do ?
   How are we going to do it ?
   

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9. These issues address
   only the solution
   And that's why we keep being
   treated as technical specialists
   

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10. These issues address
    only the solution
    It is an important discussion to
    have
    But not the problem
    But only after we've figured
    out
    what to do
    

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11. These issues address
    only the solution
    And are the hardest to refactor
    

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12. Let’s rewind
    

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13. Let’s start a new project !
    

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14. Let’s start a new project !
    We just receive the
    customer’s requirements,
    we still need to clarify a few
    things.
    But you can start the
    preliminary design phase !
    Let's do a sprint zero !
    

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15. I heard about
    « Domain Driven Design »,
    maybe we should use it !
    Yeah, that's a great idea.
    

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16. Aggregate
    Repository
    Bounded Context
    as Microservices
    Domain
    Service
    Event Driven
    CQRS
    Entity
    Value Object
    Hexagonal
    Architecture
    

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17. What are you working on ?
    There are still some
    uncertainties, but we’re
    gonna use an event-driven
    hexagonal architecture
    …
    

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18. These issues still address
    only the solution
    Aggregate
    Repository
    Bounded Context
    as Microservices
    Domain
    Service CQRS
    Entity
    Value Object
    Hexagonal
    Architecture
    Event Driven
    

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19. These issues still address
    only the solution
    This is what we call « DDD Lite »
    

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20. These issues still address
    only the solution
    And that's why we keep being
    treated as technical specialists
    

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21. www.lilobase.me
    DDD is all about
    Alignment
    @lilobase
    

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22. DDD is all about
    Alignment
    What should we do ?
    How are we going to do it ?
    

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23. DDD is all about
    Alignment
    What should we do ?
    How are we going to do it ?
    

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24. Domains & Subdomains
    Business Domain discovery
    THE Software
    Authoring
    &
    Publishing
    Printing &
    Supply
    Chain
    Customer
    Care
    Retail
    Store
    You need to acknowledge the fact that
    you have several domains
    

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25. Retail
    Store
    Inventory
    Customer
    Care
    Shipping
    Only one VP should be
    angry at a time
    Retail
    Store
    Inventory
    Customer
    Care
    Shipping
    Authoring
    &
    Publishing
    Printing &
    Supply
    Chain
    Customer
    Care
    Retail
    Store
    Domains & Subdomains
    Business Domain discovery
    

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26. Retail
    Store
    Inventory
    Customer
    Care
    Shipping
    These are neither Bounded
    Contexts nor Microservices
    Authoring
    &
    Publishing
    Printing &
    Supply
    Chain
    Customer
    Care
    Retail
    Store
    Domains & Subdomains
    Business Domain discovery
    

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27. Retail
    Store
    Inventory
    Customer
    Care
    Shipping
    These are your domains
    Authoring
    &
    Publishing
    Printing &
    Supply
    Chain
    Customer
    Care
    Retail
    Store
    Domains & Subdomains
    Business Domain discovery
    

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28. Your domains contain domains
    Domains & Subdomains
    Business Domain discovery
    Online Retail Store
    Payment
    processor
    Catalogue Invoicing
    

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29. Domain Mapping
    Business Domain Classification
    Authoring
    Plateform
    Publishing &
    Printing
    Inventory
    Management
    Payment
    Processor
    Catalogue
    Invoicing
    Shipping
    Order
    Processing
    Proofreading
    

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30. Supporting
    Subdomain
    Generic
    Subdomain
    Core
    (sub)Domain
    Key differentiator
    Domains & Subdomains
    Business Domain Classification
    Essential to the
    organization’s success
    Required for the
    organization’s success
    Critical to the
    organization’s success
    

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31. Domains & Subdomains
    Business Domain Classification
    Authoring
    Plateform
    Inventory
    Management
    Shipping
    Payment
    Processor
    Catalogue
    Invoicing
    Order
    Processing
    Publishing &
    Printing
    Proofreading
    

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32. Domains & Subdomains
    Business Domain Classification
    Authoring
    Plateform
    Inventory
    Management
    Payment
    Processor
    Catalogue
    Invoicing
    Each business context is specific
    Shipping
    Order
    Processing
    Publishing &
    Printing
    Proofreading
    

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33. Authoring
    Plateform
    Domains’ Connexion
    Reveal Business Relationships
    Inventory
    Management
    Shipping
    Catalogue
    Invoicing
    Order
    Processing
    Payment
    Processor
    It can highlight significant
    sub-domain
    Publishing &
    Printing
    Proofreading
    

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34. www.lilobase.me
    DDD is all about
    Context
    @lilobase
    

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35. From Problem to Solution
    Business Domain & Architecture alignment
    Authoring
    Plateform
    Publishing
    & Printing
    Inventory
    Management
    Shipping
    Payment
    Processor
    Catalogue
    Invoicing
    Order
    Processing
    problem
    Proofreading
    

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36. From Problem to Solution
    Business Domain & Architecture alignment
    Authoring
    Plateform
    Publishing
    & Printing
    Inventory
    Management
    Shipping
    Payment
    Processor
    Catalogue
    Invoicing
    Order
    Processing
    problem
    solution
    Payment
    processor
    Invoicing
    Order
    Processing
    Shipping
    Authoring
    Plateforme
    Inventory
    Management
    Catalogue
    Publishing
    Proofreading
    Proofreading
    Inventory E-commerce platform
    Authoring
    Publishing
    

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37. Domains & Subdomains
    Development Strategy
    Supporting
    Subdomain
    In-House development with
    external support if possible
    Generic
    Subdomain
    Outsourcing is an option
    Core
    (sub)Domain
    In-House development
    with Your best teams
    Key differentiator
    

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38. Domains & Subdomains
    Development Strategy
    Supporting
    Subdomain
    Customized Off The Shelf Software
    is an option
    Generic
    Subdomain
    Try to find Off The Shelf solution
    Cost saving opportunities
    Core
    (sub)Domain
    Custom-made software
    High Cost & Quality
    Key differentiator
    

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39. From Problem to Solution
    Business Domain & Architecture alignment
    Authoring
    Plateform
    Publishing
    & Printing
    Inventory
    Management
    Shipping
    Payment
    Processor
    Catalogue
    Invoicing
    Order
    Processing
    problem
    solution
    Payment
    processor
    Invoicing
    Order
    Processing
    Shipping
    Authoring
    Plateforme
    Inventory
    Management
    Catalogue
    Publishing
    Proofreading
    Proofreading
    Inventory E-commerce platform
    Authoring
    Publishing
    

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40. From Problem to Solution
    Business Domain & Architecture alignment
    Authoring
    Plateform
    Publishing
    & Printing
    Inventory
    Management
    Shipping
    Payment
    Processor
    Catalogue
    Invoicing
    Order
    Processing
    problem
    solution
    Proofreading
    Inventory E-commerce platform
    Authoring
    Authoring
    Plateforme Publishing
    Catalogue
    Publishing
    Proofreading
    

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41. From Problem to Solution
    Business Domain & Architecture alignment
    Inventory E-commerce
    platform
    Authoring
    Authoring
    Plateforme Publishing
    Catalogue
    Publishing
    Proofreading
    These are your bounded contexts
    

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42. P
    Authoring
    Publishing
    E-commerce
    Stripe
    ShipMonk Shopify
    Context Mapping
    Relationship Hierarchy
    These are your bounded contexts
    OHS
    OHS
    ACL
    OHS
    C/S
    

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43. Authoring
    Publishing
    E-commerce
    Specific Architecture style
    You don’t need one architectural style
    Beware of the CRUD
    ES
    CQRS
    CRUD ?
    Stripe
    ShipMonk Shopify
    

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44. Stripe
    Still no microservices
    Bounded Context ≠ Deployment units
    ShipMonk
    Authoring
    Publishing
    E-commerce
    Shopify
    Deployment Unit
    

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45. Deployment Unit
    Stripe
    Still no microservices
    Bounded Context ≠ Deployment units
    ShipMonk
    Authoring
    Publishing
    E-commerce
    Shopify
    Deployment Unit
    

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46. Domains are not immutable
    Understanding is a never-ending process
    Stripe
    ShipMonk
    Authoring
    Publishing
    E-commerce
    Shopify
    Printing
    

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47. www.lilobase.me
    DDD is all about
    Boundaries
    @lilobase
    

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48. Semantic Boundaries
    Between BC meaning are different
    Authoring Publishing
    Book
    Chapter
    Chapter
    They are not the same book
    What
    happens if
    the author
    revises his
    book?
    

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49. Semantic Boundaries
    Between BC meaning are different
    Chapter
    This is why you must start by understand
    strategically your domain
    Author
    Book
    Reviews
    Release
    Catalogue
    

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50. Semantic Boundaries
    Between BC meaning are different
    Authoring Publishing
    Book
    Chapter
    Chapter
    Book
    Chapter
    Chapter
    Inside a
    Bounded
    Context,
    Don’t
    Repeat
    Yourself
    Between
    Bounded
    Context,
    Write
    Everything
    Twice
    

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51. Don’t cross them
    Between BC meaning are different
    Authoring Publishing
    Author
    Reviews
    Author
    Book Book
    Release
    Never create relationships
    between entities from two BC
    

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52. Don’t cross them
    Between BC meaning are different
    Authoring Publishing
    Book Book
    Release
    Author
    Author
    Reviews
    This is exactly the same
    

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53. Don’t cross them
    Between BC meaning are different
    Authoring Publishing
    Book Book
    Release
    Author
    Author
    Reviews
    API API
    

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54. Same for Events
    Between BC meaning are different
    Authoring Publishing
    This is exactly the same
    Event
    Bus
    Book Book
    Release
    Author
    Author
    Reviews
    

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55. Same for Events
    Between BC meaning are different
    Authoring Publishing
    Event
    Bus
    Book Book
    Release
    Author
    Author
    Reviews
    Translator Translator
    

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56. Transactional Boundaries
    Protect your integrity
    Authoring
    Book
    Chapter
    Chapter
    Chapter
    Statistics
    Inside your
    bounded
    Context
    live
    Entities
    They are
    grouped in
    Aggregates
    

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57. Transactional Boundaries
    Protect your integrity
    Book
    Chapter
    Chapter
    Chapter
    Statistics
    They are
    retrieved
    and
    persisted
    as a whole
    Inside an
    aggregate,
    Entities
    share the
    same
    lifecycle
    

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58. Transactional Boundaries
    Protect your integrity
    Book
    Chapter
    Chapter
    Chapter
    Statistics
    Who
    ensures the
    aggregate
    integrity
    All
    interactions
    are done
    through the
    Aggregate
    Root
    Write a new chapter
    

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59. Transactional Boundaries
    Protect your integrity
    Book
    Chapter
    Chapter
    Chapter
    Statistics
    Write a new chapter
    Chapter
    Inconsistency
    

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60. Transactional Boundaries
    Protect your integrity
    Book
    Chapter
    Chapter
    Chapter
    Statistics
    But don’t
    put to much
    in it
    Author
    What
    happens if
    we delete
    the book ?
    They must share the same lifecycle
    

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61. Transactional Boundaries
    Protect your integrity
    Book
    Chapter
    Chapter
    Chapter
    Statistics
    Author
    reference
    Author
    Id
    

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62. Designing Boundaries
    Protect your domain
    Printing Team
    We need
    printing margin
    Book
    Chapter
    Chapter
    Chapter
    Release
    We need the
    colorimetric
    profile
    Printing
    margin
    Colorimetric
    profile
    API
    Publishing Team
    

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63. Designing Boundaries
    Protect your domain
    API
    We need
    printing margin
    Book
    Chapter
    Chapter
    Chapter
    Release
    We need the
    colorimetric
    profile
    Printing
    margin
    Colorimetric
    profile
    Domain Leakage
    Publishing Team Printing Team
    

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64. Designing Boundaries
    Protect your domain
    Publishing Team Printing Team
    Publishing
    API
    We
    need printing
    margin
    Book
    We
    need the
    colorimetric
    profile
    Printing
    margin
    Colorimetric
    profile
    Printing
    API
    We discovered the need
    for an ACL
    

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65. www.lilobase.me
    DDD is all about
    Compassion
    @lilobase
    

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66. A A
    A
    Ubiquitous language
    Stakeholders & Team Alignement
    Dev Domain
    Expert
    Dev
    

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67. A A
    A
    not « just » a glossary
    Ubiquitous language
    Stakeholders & Team Alignement
    Dev Domain
    Expert
    Dev
    

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68. Ubiquitous language
    Each BC has its own
    Authoring Publishing
    A A
    

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69. Ubiquitous language
    Each BC has its own
    Authoring Publishing
    A A
    A A
    It is a common cause of
    miscommunication
    

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70. Pair Programing
    The best way to share a domain understanding
    Dev Domain
    Expert
    

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71. Know your users
    They might not be who you think they are
    Dev Domain
    Expert
    Product
    Owner
    Customer User
    

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72. Know your users
    They might not be who you think they are
    Dev Domain
    Expert
    Product
    Owner
    Customer User
    He has the last word regarding
    domain implementation
    

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73. Know your users
    They might not be who you think they are
    Dev Domain
    Expert
    Product
    Owner
    Customer User
    Prioritize development &
    formalize users’ feedback
    

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74. Know your users
    They might not be who you think they are
    Dev Domain
    Expert
    Product
    Owner
    Customer User
    Power of Life and Death over the
    project
    

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75. Know your users
    They might not be who you think they are
    Dev Domain
    Expert
    Product
    Owner
    Customer User
    Too often forgotten
    

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76. Know your users
    They might not be who you think they are
    Dev Domain
    Expert
    Product
    Owner
    Customer User
    Maybe you could spend a day per
    month working with them ?
    

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77. Know your users
    They might not be who you think they are
    Dev Domain
    Expert
    Product
    Owner
    Customer User
    They design the software
    specification
    

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78. Know your users
    They might not be who you think they are
    Dev Domain
    Expert
    Product
    Owner
    Customer User
    What he understood goes
    into production
    

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79. “A loosely coupled software
    architecture and org
    structure to match” is a key
    predictor of:
    • Continuous Delivery
    Performance
    • Ability to scale
    organization and increase
    performance linearly
    This is what DDD is All About !
    — Michael Plöd (@bitboss)
    

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80. www.lilobase.me
    Thanks
    @lilobase
    https://roti.express/r/ddd-hyf
    lgo.group
    

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