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Re-Architecting Applications (Without a Rewrite!)
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Daniel Lew
February 10, 2018
Programming
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2.6k
Re-Architecting Applications (Without a Rewrite!)
Talk given at DevFestMN 2018 & MinneBar 13.
Recording here:
https://youtu.be/dKm7MKoxVIg
Daniel Lew
February 10, 2018
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Transcript
Re-architecting Applications (Without a Rewrite!) @danlew42
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
“OMG, I’m switching to MVC ASAP!” ~You Stability Some New
Architecture
Danger • Pure architectures require fresh code • Rewrites always
take longer than expected • Old code == battle tested • Expectations may not match reality
Goals • Introduce new architectures to existing codebase • Push
releases while re-architecting codebase
None
</Housing Metaphors>
Goal #1: Introduce new architectures to existing codebase
Re-Architecting Safely • Prevent overly ambitious rewrites • Prevent regrettable
architecture choices • Steps • Explore • Experiment • Expand • Embrace
Explore • What is the problem? • Define goals •
Define constraints • What are the solutions? • Brainstorm • Research
Experiment • Pick a project • Minimize work • Small
project • Simplified implementations • Minimize damage • Self-contained project • Unimportant project
Expand • Run more experiments • Pick projects wisely •
Use architecture in new ways • Pick hardest problems • Stretch architecture to limits
Embrace • Write all new code with new architecture •
Deprecate old architecture • Delete old code (optional)
Disclaimer Not an exact science
Goal #2: Push releases while re-architecting codebase
Can’t simultaneously use old and new architecture Can’t keep releasing
Old New Old + New
Parallel Development
Decouple Code BAD GOOD
Feature Flags
Shims
Shims
Offline Mode A parallel development success story
Online Only Offline Enabled
Decoupling Services Before After
Feature Flags
Shims Before After
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/
Failures With real life examples!
Explore Failures • Architecting with no purpose • Navi •
Choosing new and shiny without understanding • RxJava
Experiment Failures • Making the experiment too large • JavaScript:
The Good Parts • Not recognizing a failed experiment • Operations
Expand Failures • Choosing only easy problems • Identifiers •
Not recognizing a failed corner case • RxLifecycle
Embrace Failures • Continuing to expend effort on old architecture
• Fresh boards
Pet Peeve Telling everyone about an architecture before proving it
out!
Current Architecture Thoughts
Omni Models • Single model • Deserialized from JSON •
Written to ORM • Used by UI • Problems • Which fields are present? • How do we avoid mutability issues?
Domain-specific models • ApiModel • Only used when talking to
server • DbModel • Mutable, flexible • UiModel • Immutable, guarantees values • ApiModel <-> DbModel <-> UiModel
Unidirectional Architecture
Thanks for listening! @danlew42