CQRS & Event Sourcing in OLX

Transcript

1. CQRS
   Event Sourcing
   in OLX
   

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2. CQRS
   

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3. you can use a different
   model to update
   information than the
   model you use to read
   information
   http://martinfowler.com/bliki/CQRS.html
   „
   

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4. Command
   Query
   Responsibility
   Segregation
   

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5. Command
   Query
   Responsibility
   Segregation
   

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6. new AddCredits($userId, $amount);
   Command
   

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7. Command
   new AddCredits($userId, $amount);
   Query
   new GetCredits($userId);
   

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8. Event
   Sourcing
   

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9. http://www.martinfowler.com/eaaDev/EventSourcing.html
   „
   ensures that all
   changes to
   application state are
   stored as a sequence
   of events
   

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10. Not just can we query
    these events, we can
    also use the event log
    to reconstruct past
    states
    http://www.martinfowler.com/eaaDev/EventSourcing.html
    „
    

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11. Commad
    Event Model
    Event Storage Event Bus
    Command Handler
    Listeners
    Read Storage
    Read Model
    Query
    

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12. Commad
    Event Model
    Event Storage Event Bus
    Command Handler
    Listeners
    Read Storage
    Read Model
    Query
    Critical section - use transaction
    

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13. Commad
    Event Model
    Event Storage Event Bus
    Command Handler
    Listeners
    Read Storage
    Read Model
    Query
    Critical section - use transaction
    Treat like temporary cache
    

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14. That’s all
    

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15. E-Wallet
    Credits; Invoices; Refunds
    

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16. Wallet Credits Bonus Credits Refund Credits
    EXPIRE: X DAYS EXPIRE: X DAYS EXPIRE: X DAYS
    INVOICE: YES/NO INVOICE: YES/NO INVOICE: YES/NO
    

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17. Wallet Credits Bonus Credits Refund Credits
    EXPIRE: NEVER EXPIRE: 90 DAYS EXPIRE: 90 DAYS
    INVOICE: YES INVOICE: NO INVOICE: YES
    

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18. Opis walleta w
    Polsce
    specyfikacja
    komenty
    enventy
    Commands
    

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19. Add Wallet Credits
    Add Bonus Credits
    Add Refund Credits
    

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20. Sub Wallet Credits
    Sub Bonus Credits
    Sub Refund Credits
    SubCredits
    

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21. Opis walleta w
    Polsce
    specyfikacja
    komenty
    enventy
    Events
    

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22. Wallet CreditsWasAdded
    Bonus CreditsWasAdded
    Refund CreditsWasAdded
    

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23. Wallet CreditsWasSubtracted
    Bonus CreditsWasSubtracted
    Refund CreditsWasSubtracted
    

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24. specyfikacja
    komenty
    enventy
    7 commands
    6 events
    

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25. specyfikacja
    komenty
    enventy
    What about other
    stuff?
    

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26. Commad
    Event Model
    Event Storage Event Bus
    Command Handler
    Listeners
    Read Storage
    Read Model
    Query
    ?
    

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27. Broadway
    komponenty
    Broadway
    https://github.com/qandidate-labs/broadway
    

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28. Auditing
    log whether commands were
    successful or not
    

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29. CommandHandling
    Provides the interface and a
    CommandHandler base class for
    handling events
    

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30. Domain
    domain abstractions of the Broadway
    framework including the aggregate root,
    domain messages and domain events.
    

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31. EventDispatcher
    The component provides an event
    dispatcher interface and a simple
    implementation
    

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32. EventHandling
    provides interfaces for an event bus and event
    listeners, but also an implementation of a simple
    event bus and an event bus that will record
    published events
    

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33. EventSourcing
    Provides base classes for event sourced
    aggregate roots and entities, an event sourced
    repository implementation and testing helpers.
    

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34. EventStore
    implementation based on doctrine/dbal to store
    events in a relational database and an in-memory
    implementation that is useful for using in tests
    

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35. ReadModel
    provides storage for your read models, a
    projector implementation to create read models
    from event streams and testing helpers.
    

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36. Repository
    Component providing an abstraction of the
    storage of aggregates.
    

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37. Serializers
    provides a simple serializer interface and a
    serializer implementation based on "handwritten"
    serializers
    

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38. Commad
    Event Model
    Event Storage Event Bus
    Command Handler
    Listeners
    Read Storage
    Read Model
    Query
    Broadway
    

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39. Adding
    Wallet
    Credits
    

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42. Credits
    Query
    

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45. Lessons Learned
    

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46. Small Steps
    Don’t try to CQRS/EventSource everything
    

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47. Keep It Simple
    Avoid names like
    
    BonusCreditsWasSubtractedBecauseAdminHitSubtractBonusCr
    editsInAdminPanelEvent
    

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48. Event Storming
    is not that easy as it sounds
    

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49. It’s not RDBM
    Remember about analysts
    

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50. Code changes
    Events handle changes to data, what about changes to code?
    

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51. Synchronize
    Remember about synchronizing read layer - especially after fail
    

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52. Commad
    Event Model
    Event Storage Event Bus
    Command Handler
    Listeners
    Read Storage
    Read Model
    Query
    Critical section - use transaction
    

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53. Performance
    is not an issue - for this case
    

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54. Timezone Agnostic
    Implement your own EventStore if you want timezone aware records
    

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55. Our Team
    

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56. Paid Features
    

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57. Next challenge
    Open source Paid Features libraries
    
    with Hexagonal Architecture in mind
    

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58. Team Lead
    PHP Dev
    Junior PHP Dev
    You ?
    

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59. Łukasz Szymański
    Development Team Lead at
    @szymanskilukasz
    http://szymanskilukasz.github.io/
    https://www.linkedin.com/in/szymanskilukasz
    https://twitter.com/szymanskilukasz
    

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