Building testable APIs using functions & meshes

In this live coding talk you will learn about functional techniques that encourage separation of concerns. I will build a stateful HTTP API from highly isolated components that are easier to test than entangled spaghetti-like codebases. I will show you how tests can help us scaffold the architecture and how should we approach testing in the era of microservices. In the session I will use immutability, type parameters and function parameters as tools to implement a very practical example: Pac-Man game web server. I will code in Scala using Akka HTTP and deploy to Kubernetes with Istio service mesh.

Transcript

1. @miciek
   @miciek
   Michał Płachta
   www.michalplachta.com
   www.michalplachta.com
   Building testable APIs
   using functions & meshes
   @miciek
   

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2. @miciek
   Reinventing the Test Pyramid
   ?
   ?
   ?
   

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3. @miciek
   New Testing Pyramid: Part I
   ?
   ?
   Unit?
   

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4. @miciek
   Unit Tests
   

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5. @miciek
   What we really want...
   Fast!
   Stable!
   Quick to read/write!
   Documentation
   

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6. @miciek
   Mocking and Stubbing...
   Mocking interfaces
   with 3, 4, 5+ functions...
   Mocking interfaces
   with 0 or 1 functions...
   

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7. @miciek
   Part I
   ?
   ?
   Fast, Stable, Real
   

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8. @miciek
   Pac-Man Game Server
   ?
   Engine
   ?
   

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9. @miciek
   Pac-Man Engine Domain
   

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10. @miciek
    Pac-Man Engine Domain
    

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11. @miciek
    Pac-Man Engine Domain
    

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12. @miciek
    Pac-Man Engine Domain
    

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13. @miciek
    Immutable Pac-Man Engine
    GameState movePacMan GameState
    current new
    GameState changeDir GameState
    current new
    

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14. @miciek
    TDDing Pac-Man Engine
    

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15. @miciek
    TDDing Pac-Man Engine
    

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16. @miciek
    TDDing
    Pac-Man Engine
    Live coding
    

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17. @miciek
    TDDing Pac-Man Engine
    

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18. @miciek
    TDDing Pac-Man Engine
    

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19. @miciek
    TDDing Pac-Man Engine
    

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20. @miciek
    TDDing Pac-Man Engine
    

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21. @miciek
    Pure & Immutable
    

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22. @miciek
    TDDing Pac-Man Engine
    

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23. @miciek
    New Testing Pyramid: Part II
    ?
    Service?
    Integration?
    Fast, Stable, Real
    

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24. @miciek
    Pac-Man Game Server
    Engine
    HTTP
    ?
    

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25. @miciek
    HTTP layer requirements
    POST /games
    {
    “gridName”: “msPacManLevel1”
    }
    200 OK
    {
    “gameId”: 1
    }
    200 OK
    {
    "pacMan": {
    "position": { "x": 2, "y": 1 },
    "direction": "east"
    }
    }
    GET /games/1
    

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26. @miciek
    What we always want...
    Fast!
    Stable!
    Quick to read/write!
    Documentation
    

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27. @miciek
    Testing
    HTTP layer
    Live coding
    

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28. @miciek
    Fast, Stable, Real, Documenting
    

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29. @miciek
    Separation of Concerns
    I only know what
    I NEED to know...
    

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30. @miciek
    Pac-Man Game Server
    State
    Engine
    HTTP
    

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31. @miciek
    Requirements
    State
    holds multiple games at once
    updates (ticks) all the games
    every 200ms
    

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32. @miciek
    Holding multiple games at once
    A concurrent hash-trie or TrieMap is a concurrent
    thread-safe lock-free implementation of a hash array
    mapped trie.
    - Scala documentation
    http://lampwww.epfl.ch/~prokopec/ctries-snapshot.pdf
    

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33. @miciek
    Holding multiple games at once
    

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34. @miciek
    Ticking all the games every 200ms
    https://monix.io/docs/2x/execution/scheduler.html#schedule-with-a-delay
    

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35. @miciek
    Quick integration
    tests
    Live coding
    

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36. @miciek
    New Testing Pyramid: Part II
    ?
    Service?
    Integration?
    Fast, Stable, Real
    

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37. @miciek
    New Testing Pyramid: Part II
    ?
    Fast,
    Stable,
    Real
    

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38. @miciek
    Only one service so far...
    State
    Engine
    HTTP
    Backend service
    

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39. @miciek
    Communicating Services
    Backend service
    Frontend service
    Service Discovery
    Circuit Breaking
    Security
    Scalability & Routing
    Telemetry
    

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40. @miciek
    Testing on Production
    Backend service PROD
    Frontend service PROD
    Service Discovery
    Circuit Breaking
    Security
    Scalability & Routing
    Telemetry
    App Container App Container
    

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41. @miciek
    Testing on Production… in Isolation?
    Backend service PROD
    Frontend service PROD
    Sidecar Sidecar
    Service Discovery
    Circuit Breaking
    Security
    Scalability & Routing
    Telemetry
    App Container App Container
    

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42. @miciek
    Service Mesh
    Backend service PROD
    Frontend service PROD
    Sidecar Sidecar
    Another Service PROD
    Sidecar
    Service Mesh
    Control Plane
    

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43. @miciek
    Testing on Production… in Isolation
    Backend service PROD
    Frontend service PROD
    Sidecar Sidecar
    Backend service v2 (test)
    Sidecar
    Routing only test traffic to v2
    

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44. @miciek
    Isolated tests on
    Production
    Live coding
    

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45. @miciek
    New Testing Pyramid
    Real
    Fast,
    Stable,
    Real
    No HTTP Servers
    Function parameters
    Abstracting over data
    Routing test traffic
    Isolated tests on PROD
    

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46. @miciek
    Summary
    functional programming
    helps with
    separation of concerns
    service meshes
    may help with
    isolated testing
    ...but they are
    new & unproven
    

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47. @miciek
    Next steps
    ➔ Play around with https://www.github.com/miciek/pacman-multiplayer-fp project
    ➔ Play with Kubernetes and Istio using Katakoda
    https://www.katacoda.com/courses/istio/deploy-istio-on-kubernetes
    

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48. @miciek
    @miciek
    www.michalplachta.com
    

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49. @miciek
    @miciek
    Michał Płachta
    www.michalplachta.com
    www.michalplachta.com
    Building testable APIs
    using functions & meshes
    @miciek
    github.com/miciek/pacman-multiplayer-fp
    

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