Does Your Architecture Smell?

Is the quality of your software architecture good? Does it allow you to introduce changes easily? Is it easy enough to understand and explain? To answer these questions and to know their underlying reasons, one needs to know the issues, or more specifically smells in this context, that may occur in a software at architecture granularity. Architecture smells impair quality of the software and make the software hard to maintain and evolve. In this talk, I present seven architecture smells including Feature concentration, God component, Cyclic dependency, Scattered Functionality, and Dense Structure along with their real-world examples. Further, I discuss their impact on various dimensions of software development and propose some pragmatic strategies to avoid, detect, refactor, and manage them.

Transcript

1. Does Your Architecture Smell?
   Tushar Sharma
   

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2. Architecture smells
   Why to care?
   Types and granularities
   Examples
   How to detect
   Smells
   How to avoid
   

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3. http://www.tusharma.in
   

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4. • Continuing Growth
   • All in-use software systems will grow
   • Increasing Complexity
   • As a software system evolves, the complexity increases unless efforts are
   made to contain the complexity
   • Declining Quality
   • The quality of the software will decline unless it is rigorously maintained
   Lehman’s laws of software evolution
   

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5. Evolution of JUnit
   3.7 4.0
   4.5 4.11
   

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6. Which one is easy to work with?
   

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7. Code Quality: Why to care?
   Impacted Quality
   • Changeability
   • Understandability
   • Extensibility
   • …
   Product
   Quality
   Code/
   Design
   Quality
   Quality
   issues or
   Smells
   • Time to market
   • Reliability: Impacted by
   poor understandability
   • …
   Indicators
   • Rigidity & Fragility
   • Immobility & Opacity
   • Needless complexity
   • Needless repetition
   • …
   Productivity
   

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9. “Jugaad is a colloquial Hindi word that can mean an
   innovative fix or a simple work-around, used for solutions
   that bend rules, or a resource that can be used as such,
   or a person who can solve a complicated issue.”
   … a work-around or hack
   जुगाड़
   9
   “Jugaad”
   

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10. 10
    “Jugaad”
    

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11. “Jugaad”
    11
    

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12. “Jugaad”
    12
    

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13. “Jugaad”
    13
    

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14. “Jugaad”
    14
    

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15. Smells are Jugaads in software
    15
    

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17. What is a smell?
    …certain structures in the code that
    suggest (sometimes they scream for) the
    possibility of refactoring.
    - Kent Beck
    20 Definitions of smells: http://www.tusharma.in/smells/smellDefs.html
    

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18. Types of smells
    • Code smells
    • Implementation smells
    • Architecture smells
    • Design smells
    • Test smells
    • Performance smells
    • Configuration smells
    • Database smells
    • Models smells
    • Usability smells
    • Web smells
    • …
    

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19. Smells: Types
    http://www.tusharma.in/smells/
    

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20. Granularity of code smells
    - Implementation
    - Design
    - Architecture
    

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21. Implementation smells
    

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22. Design Smells
    

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23. Architecture Smells
    

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24. Architecture smells: examples
    

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25. Demo
    http://www.designite-tools.com
    

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26. Designite is a software design quality
    assessment tool for C#.
    Key features
    • Detects 7 architecture smells
    • Detects 19 design smells
    • Detects 11 implementation smells
    • Computes various object-oriented code metrics
    • Provides smell trend analysis of Git repositories
    • Many visualization aids including smell treemap,
    and smell sunburst
    • Detects code duplication
    • Allows customization of analysis
    • Smart tracking of detected smells
    http://www.designite-tools.com
    Academic license is free!
    

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27. God Component
    when a component is excessively large
    either in the terms of
    LOC or number of classes.
    

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28. Cyclic Dependency
    When two or more architecture
    components depend on each
    other directly or indirectly
    

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29. Stable Dependencies Principle (SDP)
    dependencies between packages should be in the direction of the
    stability of the packages.
    =
    
    (
    +
    )
    Ca - afferent coupling (or incoming dependencies)
    Ce - efferent coupling (or outgoing dependencies)
    

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30. Unstable Dependencies
    when a component depends on
    other components that are less
    stable than itself.
    IA
    < IB
    A
    B
    

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31. Feature Concentration
    A1, A2
    D1 C1, C2, C3, C4
    when a component is realizing more
    than one architectural
    concern/feature.
    In other words, the component is not
    cohesive.
    B1
    

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32. Ambiguous interface
    when a component offers only a
    single, general entry-point into the
    component.
    

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33. Scattered functionality
    when multiple components are
    responsible for realizing the same
    high-level concern
    

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34. Dense Structure
    Average degree = 2 ∗||
    ||
    when components have excessive
    and dense dependencies without
    any particular structure.
    

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35. Architecture smells in open-source projects
    Arch smells #Instances Smell density
    Cyclic dependency 34,556 0.415
    Feature concentration 17,420 0.209
    Scattered functionality 11,623 0.139
    Unstable dependency 10,195 0.122
    God component 4,774 0.057
    Ambiguous interface 852 0.010
    Dense structure 302 0.003
    Repositories: 3,209
    containing > 83
    MLOC (C#)
    

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36. Managing smells in practice
    

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37. Managing smells
    Prevent
    Detect and remove
    Awareness
    Processes
    Strategies
    

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38. Awareness
    Does the development team well aware about:
    • Smells and resultant technical debt
    • Their impact on their project
    • Code quality, clean code practices
    Train
    • Training
    • Books
    • Workshops/conferences
    • …
    

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39. Processes
    Employ pragmatic processes to bring discipline
    Review process
    • Code reviews
    Architecture governance
    • Adherence to collection of guidelines and controls
    People care about things that you measure and reward!
    

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40. Detecting and refactoring smells:
    Key strategies
    

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41. Detecting and refactoring smells: strategies
    1. Identify and track
    2. Prioritize
    3. Refactoring installments
    4. Follow the ‘Boy’s scout rule’
    5. Motivate
    6. Periodically, aim for large-scale
    refactoring
    7. Refactor, except
    

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42. Let us conclude
    

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43. A Hack
    

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44. J
    U
    G
    A
    A
    D
    Quality issues
    at architecture
    granularity
    

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45. An
    architecture
    smell
    A R C H I T E C T U R E S M E L L S
    J
    U
    G
    A
    A
    D
    

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46. Tool to detect
    smells
    A R C H I T E C T U R E S M E L L S
    O D C O M P O N E N T
    J
    U
    G
    A
    A
    D
    

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47. A way to
    improve
    A R C H I T E C T U R E S M E L L S
    O D C O M P O N E N T
    J
    U
    G
    A
    A
    D
    D
    E
    S
    I
    G
    N
    I
    T
    E
    

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48. A W A R E E S S
    G O D C O M P O N E N T
    D
    S
    I
    G
    N
    I
    T
    E
    J
    U
    G
    A
    A
    D
    A R C H I T E C T U R E S M E L L S
    

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49. Tushar Sharma
    tusharsharma@ieee.org
    http://www.tusharma.in
    Thank you!!
    Courtesy: spikedmath.com
    

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