The document discusses strategies for maintaining legacy code. It argues that a positive mindset and language is important when working on older projects. Modern techniques can and should be applied to legacy code while also respecting the past. The document recommends establishing maintenance systems like continuous integration and automated testing rather than goals to help reduce software entropy over time.

1. OLD CODE, NEW TRICKSOR, HOW I LEARNED TO LOVE LEGACY CODE AND YOU CAN, TOO.
By M. Scott Ford
Founder, Corgibytes @mscottford

2. @mscottford
WHY WAS THIS MY FAVORITE PROJECT?

3. @mscottford
DISSATISFIED?
WHY WAS I SO
• Product vs. Services?
• Desktop vs. Web?
• Startup vs. Enterprise?
• Hacker vs. Craftsman?
• Self Employed?

4. @mscottford
PRODUCT LIFE CYCLE
INTRODUCTION
GROWTH
MATURITY
DEVELOPMENT

5. @mscottford
PRODUCT LIFE CYCLE
INTRODUCTION
GROWTH
MATURITY
DEVELOPMENT
OBSCURITY
DECLINE

6. @mscottford
PRODUCT LIFE CYCLE
INTRODUCTION
GROWTH
MATURITY
DEVELOPMENT
OBSCURITY
DECLINE
MAKING

7. @mscottford
PRODUCT LIFE CYCLE
INTRODUCTION
GROWTH
MATURITY
DEVELOPMENT
OBSCURITY
DECLINE
MAKING
????

8. @mscottford
PRODUCT LIFE CYCLE
INTRODUCTION
GROWTH
MATURITY
DEVELOPMENT
OBSCURITY
DECLINE
MAKING
MENDING

9. MAKERS VS MENDERS
@mscottford

10. @mscottford
MAKERS
• Speed to Market
• Rapid Prototyping
• Minimum Viable Product
• Likes Experimenting
• Energized by Big Launch

11. @mscottford
MENDERS
• Repair Technical Debt
• Reduce Entropy
• Bug Fixes & Integrations
• Likes Stable & Steady
• Energized by Small Wins

12. @mscottford
DEVELOPER LANDSCAPE
HACKER CRAFTSMAN

13. @mscottford
DEVELOPER LANDSCAPE
HACKER CRAFTSMAN
MAKING
MENDING

14. @mscottford
DEVELOPER LANDSCAPE
HACKER CRAFTSMAN
RAPID
PROTOTYPING
MAKING
MENDING

15. @mscottford
DEVELOPER LANDSCAPE
HACKER CRAFTSMAN
RAPID
PROTOTYPING
SOLID
MAKING
MENDING

16. @mscottford
DEVELOPER LANDSCAPE
HACKER CRAFTSMAN
RAPID
PROTOTYPING
SOLID
FIRE
FIGHTING
MAKING
MENDING

17. @mscottford
DEVELOPER LANDSCAPE
HACKER CRAFTSMAN
RAPID
PROTOTYPING
SOLID
FIRE
FIGHTING
????
MAKING
MENDING

18. @mscottford
DEVELOPER LANDSCAPE
HACKER CRAFTSMAN
RAPID
PROTOTYPING
SOLID
FIRE
FIGHTING
SOFTWARE
REMODELING
MAKING
MENDING

19. SOFTWARE REMODELING
@mscottford

20. SOFTWARE REMODELING
@mscottford
activities that reduce software entropy

21. @mscottford
SOFTWARE ENTROPY

22. @mscottford
Modification increases complexity,
unless a conscious effort is made.
Using software means
continuous modification.1
2
Lehman,
M.
M.;
Belady,
L.A.
(1985),
Program
evolu=on:
processes
of
soCware
change,
Academic
Press
Professional,
Inc.,
San
Diego,
CA
SOFTWARE ENTROPY

23. @mscottford
The longer it’s been
since the last time a
program has been
modified, the more
expensive it will be
to make the next
modification.

24. BULLDOZE VS REMODEL
@mscottford

25. @mscottford
WHEN TO REMODEL?

26. @mscottford
WHEN TO REMODEL?
FEATURES
YOU HAVE

27. @mscottford
WHEN TO REMODEL?
FEATURES
YOU HAVE
FEATURES
YOU NEED

28. @mscottford
WHEN TO REMODEL?
FEATURES
YOU HAVE
FEATURES
YOU NEED
REMODELING
JUSTIFICATION

29. @mscottford
REMODELING PRINCIPLES

30. @mscottford
REMODELING PRINCIPLES
Language
Matters

31. project?
How do you describe a
LEGACY
@mscottford

32. @mscottford
WHAT COLOR IS YOUR FIELD?

33. • Talking positively about our work helps us feel good about it.
• Consider the following:
@mscottford
LANGUAGE MATTERS
NEGATIVE POSITIVE
Legacy
Brownfield
Rescue
Spaghetti Code
Antiquated
Existing Code
Restore
Remodel
Revitalize
Vintage/Classic

34. • Some terms used by the Agile community begin to break down
when talking about existing projects.
• Consider the following:
– Sprint vs. Iteration
– Estimate vs. Forecast
@mscottford
LANGUAGE MATTERS

35. @mscottford
Modern
Techniques
REMODELING PRINCIPLES
Language
Matters

36. • Would a doctor treat you using only medical knowledge
available in the year you were born?
• When working on an old house, would you limit yourself to only
tools available the year it was built?
• You DO NOT have to limit yourself to old tools and techniques.
@mscottford
USE MODERN TECHNIQUES

37. @mscottford
Modern
Techniques
REMODELING PRINCIPLES
Language
Matters
Respect
The Past

38. • Look at work as a form of software archaeology.
• Practice giving and receiving critiques.
• Retrospective Prime Directive becomes invaluable. Reserve
judgement.
“Regardless of what we discover, we understand and truly believe that
everyone did the best job they could, given what they knew at the time, their
skills and abilities, the resources available, and the situation at hand.”
@mscottford
RESPECT THE PAST

39. • How to give a good critique:
–Critique the code: never the author.
–Call attention to the good things,
as well as opportunities for improvement.
–Make it clear that you are stating opinion and not fact.
• Practice at http://exercism.io
• git blame
@mscottford
RESPECT THE PAST

40. @mscottford
Modern
Techniques
Systems,
Not Goals
REMODELING PRINCIPLES
Language
Matters
Respect
The Past

41. • Goals work great for initial launch, not so well for maintenance.
– Ex: Better to establish system where tests are added with
every commit than set a “goal” of 100% test coverage.
– Continuous Integration
– Continuous Deployment
– Automated Code Review
@mscottford
SYSTEMS, NOT GOALS

42. • Some of our favorite tools for creating maintenance systems:
– Style Cops (rubocop, FxCop)
– Linters (jslint, csslint, xmllint)
– Quality (Code Climate, BitHound)
– Continuous Monitoring (Honeybadger, Airbrake, New Relic)
– Continuous Deployment & Integration (CodeShip, Jenkins,
Travis CI, Circle CI)
– Chat-Ops (Slack, Gitter, HipChat) @mscottford
SYSTEMS, NOT GOALS

43. QUESTIONS?
@mscottford

44. @mscottford
Contact Info
@mscottford
corgibytes.com