Taming the Codebase: Strategies for Refactoring Legacy Code

Inheriting a codebase riddled with technical debt is a common developer nightmare. This talk tackles the seemingly paradoxical challenge of making unmaintainable code maintainable. We'll explore real-world scenarios where new developers face a tangled mess left behind by previous team members. Through practical techniques and battle-tested approaches, we'll delve into strategies for safely refactoring and potentially migrating code without introducing new errors. The session will cover topics like: Identifying Code Smells: Learn to recognize common signs of unmaintainable code and prioritize your refactoring efforts. Test-Driven Refactoring: Explore how to write unit tests that not only identify bugs but also guide your refactoring process. Incremental Improvement: Discover how to break down complex refactoring tasks into smaller, manageable steps that minimize risk. Effective Communication: Learn how to collaborate with stakeholders and the remaining development team to ensure successful codebase improvements. This session is designed for developers who have inherited legacy code and are looking for practical strategies to tame the codebase monster.

Transcript

1. 10/14/24
2. Wir entwickeln Softwarelösungen: Cloud-native Softwareentwicklung Data insights Beratung, Workshops und Reviews Wir steigern die Effizienz von IT- Abteilungen: Platform Engineering Cloud Infrastructure Software Modernisierung Was wir machen?
3. 3 ”TAMING THE CODEBASE MONSTER"
4. 4 WHAT IS LEGACY?
5. 5 WHAT IS LEGACY CODE? • No longer maintained or supported by the original developers. • Code was written in a now-obsolete programming language or for a platform that is no longer in demand. • The code is difficult or very costly to modify. • There are no automated tests or (up-to-date) documentation for the code.
6. 6 EXAMPLE • CR for a simple Application:
7. 7 EXAMPLE
8. 8 MIGRATION STRATEGIES (6RS) 1. Rehost (Lift and Shift): • Applications are moved to a new infrastructure (often the cloud) without changes to the underlying code. • Pro: Quick and easy to implement, requires no code changes. • Con: Doesn’t fully leverage cloud benefits; can be more expensive and inefficient in the long term.
9. 9 MIGRATION STRATEGIES (6RS) 2. Replatform • Minor changes to the application to optimize it for the new environment without rearchitecting. • Pro: Improves efficiency and cost while utilizing some cloud benefits • Con: Requires moderate development resources and effort.
10. 10 MIGRATION STRATEGIES (6RS) 3. Replace • Replacing the legacy application with a new solution, often a SaaS (Software as a Service) product. • Pro: Less maintenance and faster to implement. • Con: Potential limitations due to out-of-the-box features and the complexity of data migration.
11. 11 MIGRATION STRATEGIES (6RS) 4. Retire • Applications or parts of them are not migrated but decommissioned because they are no longer needed. • Pro: Reduces complexity and cost. • Con: Requires a thorough analysis of system dependencies before retiring.
12. 12 MIGRATION STRATEGIES (6RS) 5. Retain • Applications remain in their current environment, either because they aren’t ready for migration or because they will be addressed later. • Pro: Avoid unnecessary changes where no immediate value can be gained. • Con: Delays future migration.
13. 13 MIGRATION STRATEGIES (6RS) 6. Refactoring / Rearchitecting • Fundamental redesign of the application architecture to take full advantage of the new plattform. • Pro: Maximum flexibility and ability to utilize advanced features of the new platform. • Con: Higher cost, complexity, and time-consuming.
14. 14 SOFTWARE MIGRATION INSURANCE SOFTWARE Requirements: • Host to Cloud migration • Refactor existing Java applications • Cobol to Java refactoring • Infrastrucutre replacement • Step by step migration
15. 15 SOFTWARE MIGRATION INSURANCE SOFTWARE
16. 16 SOFTWARE MIGRATION INSURANCE SOFTWARE Analyzing the code - How significant is the technical debt? - Analysis of infrastructure and surrounding systems. - Is a documentation available? - Do we have tests? - How much will it cost? How long will it take?
17. 17 SOFTWARE MIGRATION INSURANCE SOFTWARE Strangler Fig Pattern:
18. 18 SOFTWARE MIGRATION INSURANCE SOFTWARE
20. 20 SOFTWARE MIGRATION INSURANCE SOFTWARE - Golden Master Technique
21. 21 SOFTWARE MIGRATION INSURANCE SOFTWARE - Test-Driven Refactoring o write tests for the existing codebase - The Boy Scout Rule o Leave it cleaner than you found it
22. 22 SOFTWARE MIGRATION INSURANCE SOFTWARE
24. 24 FAILED PROJECT
25. 25 FAILED PROJECT
26. 26 FAILED PROJECT - What went wrong? I will skip the tests
27. 27 THANK YOU FOR YOUR ATTENTION
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