Re-Architecting Applications (Without a Rewrite!)

Transcript

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

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   architecture: the structure and design of a system or product

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

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

   Architecture
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    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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    Goals • Introduce new architectures to existing codebase • Push

    releases while re-architecting codebase
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    </Housing Metaphors>

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    Goal #1: Introduce new architectures to existing codebase

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

    architecture choices • Steps • Explore • Experiment • Expand • Embrace
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    Explore • What is the problem? • Define goals •

    Define constraints • What are the solutions? • Brainstorm • Research
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    Experiment • Pick a project • Minimize work • Small

    project • Simplified implementations • Minimize damage • Self-contained project • Unimportant project
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    Expand • Run more experiments • Pick projects wisely •

    Use architecture in new ways • Pick hardest problems • Stretch architecture to limits
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    Embrace • Write all new code with new architecture •

    Deprecate old architecture • Delete old code (optional)
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    Disclaimer Not an exact science

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    Goal #2: Push releases while re-architecting codebase

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

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    Old New Old + New

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    Parallel Development

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    Decouple Code BAD GOOD

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    Feature Flags

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    Shims

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    Shims

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    Offline Mode A parallel development success story

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    Online Only Offline Enabled

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    Decoupling Services Before After

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    Feature Flags

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    Shims Before After

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    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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    Failures With real life examples!

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    Explore Failures • Architecting with no purpose • Navi •

    Choosing new and shiny without understanding • RxJava
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    Experiment Failures • Making the experiment too large • JavaScript:

    The Good Parts • Not recognizing a failed experiment • Operations
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    Expand Failures • Choosing only easy problems • Identifiers •

    Not recognizing a failed corner case • RxLifecycle
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    Embrace Failures • Continuing to expend effort on old architecture

    • Fresh boards
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    Pet Peeve Telling everyone about an architecture before proving it

    out!
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    Current Architecture Thoughts

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

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

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    Thanks for listening! @danlew42