Mine Your Own Code
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The document discusses the challenges of determining when and how to refactor code, emphasizing the importance of analyzing software evolution, code decay, and technical debt. It introduces methodologies for identifying 'god classes,' code churn, and architectural weaknesses through mining software repositories and utilizing tools like Code Maat. Ultimately, it aims to provide metrics that guide refactoring efforts by highlighting the business value and urgency of maintaining code quality.
Mine Your Own Code
- 1. MINE YOUR OWN CODE
- 2. vs
- 3. How do I know what to refactor?
- 4. BACKGROUND • Married for 25+ years • Working as software developer/architect for 25 years • Weighs 20+ kg more • Will work 15(+/-?) more years trying to answer that question
- 5. EXTENDA
- 6. HOW SOFTWARE EVOLVE OVER TIME Time Very often becomes
- 7. POTENTIAL INDICATORS Code Decay Lack of design patterns Architecture violations Code Smell God Class Data Class Code Clones Tradition Breaker Intensive Coupling …
- 8. SHOW ME THE NUMBERS I want to refactor the code! Why? What’s the business value? Show me the numbers! ?
- 9. FIND THE HOTSPOTS Problems Degraded velocity Long and breaking builds Increasing size and complexity SLA issues Diagnose/Action Test Code Review Refactor
- 11. WHERE TO START?
- 12. LARGE/GOD CLASS ATFD > 5 Access to foreign data WMC > 46 Weighted method count TCC > 0.33 Tight class cohesion God Class
- 14. MINING SOFTWARE REPOSITORIES Uses other sources as well Version Control Systems (Git, Mercurial, Perforce, …) Incident Systems (Jira, Bugtracker, ALM, …) Communication Platforms (Stack Overflow, Intranets, …) Build Servers (Jenkins, TeamCity, GO, …) Review Tools (Swarm, Organization Schemas … Adds time aspect Time
- 15. MINING SOFTWARE REPOSITORIES Mining software repositories gives us technical and social/ organizational information that we can’t derive from a snapshot.
- 16. GOD CLASS ATFD > 5 Access to foreign data WMC > 46 Weighted method count TCC > 0.33 Tight class cohesion God Class God classes are 4-17 times more defect prone God classes are 5-7 times more change prone
- 17. DESIGN/TECHNICAL DEBT Finding the sweetspot When do the cost of maintenance exceed the cost to refactor – Value of debt (how much is it going to cost to fix it?) – Interest rate (how much does it slow down development?) – Probability (what is the chance that the debt affects productivity?)
- 18. CODE CHURN
- 19. CODE CHURN Research has shown that frequent changes to complex code generally indicate declining quality The number of times code changes is a better predictor of defects than pure size Modules that change frequently are linked to maintenance problems and low quality (An Empirical Study on the Impact of Duplicate Code) Including a measure of change in the prior release is an essential component of our fault prediction method. Individually, counts of adds and modifications outperform counts of deletes, while the sum of all three counts was most effective (Does Measuring Code Change Improve Fault Prediction?)
- 20. CODE MAAT Command line tool to analyse VCS (Git, Mercurial, Subversion, Team Foundation Server, Perforce) Input : VCS log file for the last X days/months/year(s) Output : File Statistics (Number of files, age, …) Organizational Metrcis (number of authors, code ownership, …) Coupling Code Churn
- 22. DEMO – CODE CHURN Code Maat https://github.com/adamtornhill/code-maat Docker image https://github.com/peternorrhall/code-maat
- 23. DEMO EMPEAR Code Maat + Hotspots Settings/Filtering and Visualization Performance Only support for Git
- 24. EXTENDA - MSR Time Changelist/Files Job Defect Requirement Refactoring Code Analysis Categorisation
- 26. FINDINGS New module Self Checkout Client (device integration) A lot of development 2014 A lot of defects and refactorings in 2015 forthe files with highest code churn and complexity. In accordance with the result in Empear XML complexity as well
- 27. STREAMS Task streams for larger work Purpose stable main main dev @ @ task
- 28. TEMPORAL COUPLING Static code dependencies (Structure 101 on the Spring project)
- 29. TEMPORAL COUPLING TestClassA ClassA ClassB Research • Change coupling points to architectural weakness • Hotspots of refactoring candidates • Helps comprehension of system modularization • Spotting of misplaced components • Correlates with defects (in some cases) Module A Module B
- 30. DEMO - TEMPORAL COUPLING
- 31. EMPEAR
- 32. GRAPHVIZ
- 33. TEMPORAL COUPLING – USE CASES Find patterns (.properties should be changed together) Find hidden dependencies (modules) Lack of unit tests or too high velocity of unit tests Interesting to see how it changes over time
- 34. ORGANIZATION AND OWNERSHIP Time Ownership where person is about to leave or has left + Age of code
- 35. WHAT IS YOUR BUSINESS CASE? Do you need to care about it in the first place? How long will your product/system live? Extenda 20+ years for some of our products Data Scientist spend most of their time cleaning data Remove ”Build user”, Streams, … What type of commit – defect/refactor/new feature (explicit labeling works well) Finding the False Positives Use the metrics you have
- 36. USE AND VISUALIZE YOUR DATA Free material from www.gapminder.org
- 37. THE GOAL I want to refactor the code! Why? Show me the numbers! No problem Boss!
- 38. QUESTIONS
- 39. THANK YOU FOR LISTENING! Please ask or give feedback Email : peter.norrhall@extenda.com LinkedIn : https://www.linkedin.com/in/peternorrhall Twitter : https://twitter.com/peternorrhall
- 40. REFERENCES "Making Software, What Really Works, and Why We Believe It", Oram/Wilson "Object-Oriented Metrics in Practice", Lanza/Marinescu "Your Code as a Crime Scene", Tornhill "Investigating the Impact of Design Debt on Software Quality", Zazworka/Seaman/Shull/Shaw MSR International Conference - http://2016.msrconf.org/
- 41. TOOLS Code Maat - https://github.com/adamtornhill/code-maat Code Maat Docker Image - https://github.com/peternorrhall/code-maat Docker - https://www.docker.com/ Empear – http://www.empear.com Graphviz – http://www.graphviz.org Git - https://git-scm.com/ Git-P4 - https://git-scm.com/docs/git-p4 MS Excel - https://products.office.com/sv-se/excel Pentaho - http://community.pentaho.com/ Perforce - https://www.perforce.com/ R Studio - https://www.rstudio.com/ SonarQube - http://www.sonarqube.org/ Structure101 - http://structure101.com/