Taming the Codebase: Strategies for Refactoring Legacy Code

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10/14/24

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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?

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3 ”TAMING THE CODEBASE MONSTER"

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4 WHAT IS LEGACY?

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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 • No longer maintained or supported by the original developers.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.

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6 EXAMPLE • CR for a simple Application:

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7 EXAMPLE

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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.

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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.

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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.

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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.

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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.

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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.

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14 SOFTWARE MIGRATION INSURANCE SOFTWARE Requirements: • Host to Cloud migration • Refactor existing Java applications • Cobol to Java refactoring • Infrastrucutre replacement • Step by step migration

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15 SOFTWARE MIGRATION INSURANCE SOFTWARE

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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?

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17 SOFTWARE MIGRATION INSURANCE SOFTWARE Strangler Fig Pattern:

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18 SOFTWARE MIGRATION INSURANCE SOFTWARE

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20 SOFTWARE MIGRATION INSURANCE SOFTWARE - Golden Master Technique

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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