Code Refactoring or Rewrite: How to Properly Dispose of Legacy Code
- 1. Refactor vs. Rewrite by Roman Labunsky datree.io
- 2. AGENDA ● How to choose between the two ● A third option! ● A Practical example ● About me ● About datree ● What is legacy code? ● Refactor vs. Rewrite
- 3. ● 33 Years old ● Have 2 dogs ● Love unboxing ● Love clean code and elegant architecture ● Engineering manager at datree WHO AM I
- 4. See Your R&D Stack in Action Gain full visibility into your code components Enhance collaboration
- 5. Old technology | Old language | Old developer | No tests | Time Legacy code is source code that relates to a no-longer supported or manufactured operating system or other computer technology. - Wikipedia WHAT IS LEGACY CODE?
- 6. A rewrite is the act or result of re-implementing a large portion of existing functionality without re-use of its source code or writing inscription. Refactor Rewrite Fast iterations Long term commitment Same underlying technology/architecture Free to choose technology Same Project New Project/Component Maintain one system Maintain two systems(at least) Code refactoring is the process of restructuring existing computer code — changing the factoring — without changing its external behavior. REFACTOR VS. REWRITE
- 7. Programmers are, in their hearts, architects, and the first thing they want to do when they get to a site is to bulldoze the place flat and build something grand. - Joel Spolsky How to Choose? ● Are you doing a larger architectural shift? Microservices? Serverless? ● Will current underlying technology support future requirements? ● Is it the core of your business?
- 8. YOU DON’T HAVE TO CHOOSE!
- 9. 1. Write new code. 2. Intercept events triggering old code with new code. 3. Capture the assets! 4. Rinse repeat 1-3 till old code is “strangled” 5. Retire old system STRANGLER APPLICATION
- 10. USERS SERVICE DB Update UserGet UserCreate User Delete User
- 11. Update UserGet UserCreate User Delete User Update UserGet UserCreate User Delete User OLD USER SERVICE NEW USER SERVICE PHASE #1 Trigger
- 12. Update UserGet UserCreate User Delete User Update UserGet UserCreate User Delete User OLD USER SERVICE NEW USER SERVICE PHASE #2 Trigger
- 13. Update UserGet UserCreate User Delete User Update UserGet UserCreate User Delete User OLD USER SERVICE NEW USER SERVICE PHASE #3 Trigger
- 14. Update UserGet UserCreate User Delete User Update UserGet UserCreate User Delete User OLD USER SERVICE NEW USER SERVICE PHASE #4 Trigger
- 15. Update UserGet UserCreate User Delete User Update UserGet UserCreate User Delete User OLD USER SERVICE NEW USER SERVICE PHASE #5 Trigger
- 16. NEW USERS SERVICE DB Update UserGet UserCreate User Delete User
- 18. THANK YOU
Editor's Notes
- #6: As soon as it’s tagged as legacy it becomes the badlands, people forget the rules and do what they want, thinking it’s soon be dead.