Re-Architecting Applications (Without a Rewrite!)

Talk given at DevFestMN 2018 & MinneBar 13.

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

Transcript

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

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

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

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

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10. Danger
    • Pure architectures require fresh code
    
    • Rewrites always take longer than expected
    
    • Old code == battle tested
    
    • Expectations may not match reality
    

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11. Goals
    • Introduce new architectures to existing codebase
    
    • Push releases while re-architecting codebase
    

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13. 
    

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

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15. Re-Architecting Safely
    • Prevent overly ambitious rewrites
    
    • Prevent regrettable architecture choices
    
    • Steps
    
    • Explore
    
    • Experiment
    
    • Expand
    
    • Embrace
    

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16. Explore
    • What is the problem?
    
    • Define goals
    
    • Define constraints
    
    • What are the solutions?
    
    • Brainstorm
    
    • Research
    

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17. Experiment
    • Pick a project
    
    • Minimize work
    
    • Small project
    
    • Simplified implementations
    
    • Minimize damage
    
    • Self-contained project
    
    • Unimportant project
    

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18. Expand
    • Run more experiments
    
    • Pick projects wisely
    
    • Use architecture in new ways
    
    • Pick hardest problems
    
    • Stretch architecture to limits
    

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19. Embrace
    • Write all new code with new architecture
    
    • Deprecate old architecture
    
    • Delete old code (optional)
    

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20. Disclaimer
    Not an exact science
    

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

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

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23. Old
    New
    Old + New
    

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24. Parallel Development
    

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25. Decouple Code
    BAD GOOD
    

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26. Feature Flags
    

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27. Shims
    

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28. Shims
    

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29. Offline Mode
    A parallel development success story
    

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30. Online Only Offline Enabled
    

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31. Decoupling Services
    Before After
    

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32. Feature Flags
    

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33. Shims
    Before After
    

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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/
    

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35. Failures
    With real life examples!
    

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36. Explore Failures
    • Architecting with no purpose
    
    • Navi
    
    • Choosing new and shiny without understanding
    
    • RxJava
    

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37. Experiment Failures
    • Making the experiment too large
    
    • JavaScript: The Good Parts
    
    • Not recognizing a failed experiment
    
    • Operations
    

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38. Expand Failures
    • Choosing only easy problems
    
    • Identifiers
    
    • Not recognizing a failed corner case
    
    • RxLifecycle
    

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

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

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41. Current Architecture Thoughts
    

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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?
    

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43. Domain-specific models
    • ApiModel
    
    • Only used when talking to server
    
    • DbModel
    
    • Mutable, flexible
    
    • UiModel
    
    • Immutable, guarantees values
    
    • ApiModel <-> DbModel <-> UiModel
    

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44. Unidirectional Architecture
    

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45. Thanks for listening!
    @danlew42
    

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