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
2. @miciek Reinventing the Test Pyramid ? ? ?
3. @miciek New Testing Pyramid: Part I ? ? Unit?
4. @miciek Unit Tests
5. @miciek What we really want... Fast! Stable! Quick to read/write! Documentation
6. @miciek Mocking and Stubbing... Mocking interfaces with 3, 4, 5+ functions... Mocking interfaces with 0 or 1 functions...
7. @miciek Part I ? ? Fast, Stable, Real
8. @miciek Pac-Man Game Server ? Engine ?
9. @miciek Pac-Man Engine Domain
10. @miciek Pac-Man Engine Domain
11. @miciek Pac-Man Engine Domain
12. @miciek Pac-Man Engine Domain
13. @miciek Immutable Pac-Man Engine GameState movePacMan GameState current new GameState changeDir GameState current new
14. @miciek TDDing Pac-Man Engine
15. @miciek TDDing Pac-Man Engine
16. @miciek TDDing Pac-Man Engine Live coding
17. @miciek TDDing Pac-Man Engine
18. @miciek TDDing Pac-Man Engine
19. @miciek TDDing Pac-Man Engine
20. @miciek TDDing Pac-Man Engine
21. @miciek Pure & Immutable
22. @miciek TDDing Pac-Man Engine
23. @miciek New Testing Pyramid: Part II ? Service? Integration? Fast, Stable, Real
24. @miciek Pac-Man Game Server Engine HTTP ?
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
26. @miciek What we always want... Fast! Stable! Quick to read/write! Documentation
27. @miciek Testing HTTP layer Live coding
28. @miciek Fast, Stable, Real, Documenting
29. @miciek Separation of Concerns I only know what I NEED to know...
30. @miciek Pac-Man Game Server State Engine HTTP
31. @miciek Requirements State holds multiple games at once updates (ticks) all the games every 200ms
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
33. @miciek Holding multiple games at once
34. @miciek Ticking all the games every 200ms https://monix.io/docs/2x/execution/scheduler.html#schedule-with-a-delay
35. @miciek Quick integration tests Live coding
36. @miciek New Testing Pyramid: Part II ? Service? Integration? Fast, Stable, Real
37. @miciek New Testing Pyramid: Part II ? Fast, Stable, Real
38. @miciek Only one service so far... State Engine HTTP Backend service
39. @miciek Communicating Services Backend service Frontend service Service Discovery Circuit Breaking Security Scalability & Routing Telemetry
40. @miciek Testing on Production Backend service PROD Frontend service PROD Service Discovery Circuit Breaking Security Scalability & Routing Telemetry App Container App Container
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
42. @miciek Service Mesh Backend service PROD Frontend service PROD Sidecar Sidecar Another Service PROD Sidecar Service Mesh Control Plane
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
44. @miciek Isolated tests on Production Live coding
45. @miciek New Testing Pyramid Real Fast, Stable, Real No HTTP Servers Function parameters Abstracting over data Routing test traffic Isolated tests on PROD
46. @miciek Summary functional programming helps with separation of concerns service meshes may help with isolated testing ...but they are new & unproven
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
48. @miciek @miciek www.michalplachta.com
49. @miciek @miciek Michał Płachta www.michalplachta.com www.michalplachta.com Building testable APIs using functions & meshes @miciek github.com/miciek/pacman-multiplayer-fp