The problem

Old systems were written when processor time was cheap and energy invisible. They run continuously, are replicated widely and have never been profiled, but nobody wants to touch them.

The fix you can use today

• Rank systems by how much they run and how many instances exist.
• Map and test the top candidates before changing them.
• Fund modernisation as maintenance with a measured energy and cost outcome.

Published research puts legacy code at 60 to 80% of the software still in use. GreenCode's legacy work starts from this.

Tools that help

• cloc: counts lines of code by language, a quick way to size a codebase
• SonarQube: static analysis for code smells, bugs and security issues, with quality gates in CI
• OpenRewrite: automated refactoring recipes applied across a whole codebase

How GreenCode helps

GreenCode helps tackle this by mapping a legacy codebase and generating the tests and documentation it never had. Only then does it refactor, returning each change as a pull request you can review. More on this.

Tags

#legacy#cost#refactoring

Sources

• Legacy code modernisation
• Legacy share of enterprise systems (International Journal of Automation and Computing)

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