Re-Architecting Applications (Without a Rewrite!)

Talk given at DevFestMN 2018 & MinneBar 13.

Recording here: https://youtu.be/dKm7MKoxVIg

1. Re-architecting Applications (Without a Rewrite!) @danlew42
2. architecture: the structure and design of a system or product
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
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