Re-Architecting Applications (Without a Rewrite!)

Transcript

1. Re-architecting Applications (Without a Rewrite!) @danlew42

2. architecture: the structure and design of a system or product

3. None
4. None
5. None
6. None
7. None

8. “Model-View- Controller is the best thing since sliced bread.” ~Evil

   Dan Lew

9. “OMG, I’m switching to MVC ASAP!” ~You Stability Some New

   Architecture

10. Danger • Pure architectures require fresh code • Rewrites always

    take longer than expected • Old code == battle tested • Expectations may not match reality

11. Goals • Introduce new architectures to existing codebase • Push

    releases while re-architecting codebase
12. None

13. </Housing Metaphors>

14. Goal #1: Introduce new architectures to existing codebase

15. Re-Architecting Safely • Prevent overly ambitious rewrites • Prevent regrettable

    architecture choices • Steps • Explore • Experiment • Expand • Embrace

16. Explore • What is the problem? • Define goals •

    Define constraints • What are the solutions? • Brainstorm • Research

17. Experiment • Pick a project • Minimize work • Small

    project • Simplified implementations • Minimize damage • Self-contained project • Unimportant project

18. Expand • Run more experiments • Pick projects wisely •

    Use architecture in new ways • Pick hardest problems • Stretch architecture to limits

19. Embrace • Write all new code with new architecture •

    Deprecate old architecture • Delete old code (optional)

20. Disclaimer Not an exact science

21. Goal #2: Push releases while re-architecting codebase

22. Can’t simultaneously use old and new architecture Can’t keep releasing

23. Old New Old + New

24. Parallel Development

25. Decouple Code BAD GOOD

26. Feature Flags

27. Shims

28. Shims

29. Offline Mode A parallel development success story

30. Online Only Offline Enabled

31. Decoupling Services Before After

32. Feature Flags

33. Shims Before After

34. Offline Mode • Project length: 1.5 years • Never stopped

    releasing • Minimal UI changes • Gradual experimentation via flags • Switched over without anyone noticing • https://tech.trello.com/sync-architecture/

35. Failures With real life examples!

36. Explore Failures • Architecting with no purpose • Navi •

    Choosing new and shiny without understanding • RxJava

37. Experiment Failures • Making the experiment too large • JavaScript:

    The Good Parts • Not recognizing a failed experiment • Operations

38. Expand Failures • Choosing only easy problems • Identifiers •

    Not recognizing a failed corner case • RxLifecycle

39. Embrace Failures • Continuing to expend effort on old architecture

    • Fresh boards

40. Pet Peeve Telling everyone about an architecture before proving it

    out!

41. Current Architecture Thoughts

42. Omni Models • Single model • Deserialized from JSON •

    Written to ORM • Used by UI • Problems • Which fields are present? • How do we avoid mutability issues?

43. Domain-specific models • ApiModel • Only used when talking to

    server • DbModel • Mutable, flexible • UiModel • Immutable, guarantees values • ApiModel <-> DbModel <-> UiModel

44. Unidirectional Architecture

45. Thanks for listening! @danlew42