Video: https://www.youtube.com/watch?v=JKYktDRoRxw Pycon 2015 Montreal Nina Zakharenko Technical Debt - The Code Monster in Your Closet Description Technical debt is the code monster hiding in everyone's closet. If you ignore it, it will terrorize you at night. To banish it and re-gain your productivity, you'll need to face it head on. Abstract I've worked at many institutions with many programming languages over the past 8 years They all have technical debt. Putting on a band-aid and ignoring the real issues can be disastrous. We'll go through several case studies, review big red flags, and learn how to start chipping away at the problem with confidence.

1. TECHNICAL DEBT
!
THE CODE MONSTER IN
YOUR CLOSET
Nina Zakharenko
@nnja

2. WHAT IS
TECHNICAL
DEBT?

3. (BOTH BUSINESS & TECHNICAL)
A SERIES OF
BAD DECISIONS

4. WHICH LEAD TO
ERROR PRONE CODE
& ARCHITECTURE

5. … AND USING MORE
TO ACCOMPLISH
RESOURCES
LESS

6. What decisions were
made in the past

7. that prevent me from
getting sh** done today?

8. WHAT CAUSES IT?

9. ME.
AND YOU.

10. Mistakes I Made Early On
Not knowing how to say NO to features
Not seeing the value in Unit Tests

11. Mistakes I Made Early On
Overly Optimistic Estimates
Putting releases over good design & reusable code

12. TIME CRUNCH
The project was due yesterday!
I’ll take a shortcut, and clean up the mess tomorrow.

13. UNNEEDED COMPLEXITY
Lines of code committed != amount of work
accomplished.

14. Step 1: Have a problem.
Step 2: Look up How to do it on Stack Exchange
LACK OF UNDERSTANDING
Step 3: Copy and Paste it into your codebase
Step 4: ???
Step 5: Bugs!

15. CULTURE OF DESPAIR
This is already a heap of trash.
Will anyone really notice if I add something to the top?

16. RED FLAGS
Houston, We Have a Problem.

17. CODE SMELLS?
Not bugs.
An indication of a deeper problem.

18. CODE SMELLS
• Half implemented features
• No or poor documentation

19. CODE SMELLS
• Commented out code, incorrect comments
• No tests or broken tests

20. POOR DOCUMENTATION
class OrganicGlutenFreePizzaFactory:
def get_dough(self):
"""
Return amazing, organic, GMO and Gluten Free Dough
"""
# ran out of organic gluten free, use the other
stuff.
!
# return 'organic gluten free dough'
return 'gmo white pesticide dough'

21. ARCHITECTURE & DESIGN… SMELLS
• Parts of the code that no one wants to touch
• Changing code in one area breaks other parts of the
system
• Severe outages caused by frequent & unexpected
bugs

22. GOOD DESIGN
Implementing new features comes easily.
BAD DESIGN
Shoe-horning new features into the system.

23. PYTHON SPECIFIC SMELLS

24. Functionality Changes,
Variable names Don’t.
employees = ['John', 'Mary', 'Dale']
!
employees = 'Bob'
!
employees[0]

25. Monkey Patching
def new_init(self):
pass
!
some_library.SomeClass.__init__ = new_init

26. What exactly does that decorator do?
def decorator_evil(target):
return False
!
@decorator_evil
def target(a,b):
return a + b
!
>>> target
False
!
>>> target(1,2)
TypeError: 'bool' object is not callable

27. Circular Dependencies
def some_function(x):
from some.module import some_method
some_method(x)

28. CASE STUDIES

29. IRS CHIEF:
"We Still Have Applications That Were Running When
JFK Was President"

30. 50 Year old Technology
"And we continue to use the COBOL programming
language, it is extremely difficult to find IT experts who
are versed in this language.”

31. It’s not just the IRS.
Banks & Financial Insitutions
Universities
Air Traffic Control
!
… all use COBOL.

32. STORY TIME
I used to work in finance.
At the time I was there, all of the banking systems were
run on mainframes.
The bankers were getting frustrated. They wanted a UI.

33. IDEA!
Let’s write a fancy new web front end.
It’ll do ALL the things.

34. BUT
Rewriting the backend is too expensive.
!
It already does what we need.
!
Let’s leave the mainframe.

35. CURSORS
The mainframe would output a text screen from a
program result, based on a query.
The results would be parsed by reading variables from
the screen in certain positions.

36. RESULT?
The new system was incredibly slow.
And error prone.
!
After months of work, the multi-million dollar rewrite
was scrapped.

37. YOU CAN PUT LIPSTICK ON A PIG

38. THE MVP
(Minimum Viable Product)
Get the product to early customers as soon as possible.

39. A GREAT IDEA
I worked on a project that was created by a lone
developer in a coffee fueled 48 hours.
It was a great success.

40. THERE WAS A PROBLEM
Years went on, but the initial code and design didn’t go
away.
Instead, it became the base for an expanding project,
with expanding features.
Worse, there was never any time to refactor.

41. SCOPE CREEP
Features that someone thought was a good idea one
day, stuck around forever.
“In case we need them. Later.”

42. SAD DEVELOPERS
That made it feel like your fault.
When a release was pushed, something was bound to
break.
There were no working tests.

43. GRINDING TO A HALT
Development time for new features skyrocketed.
The project was deemed too difficult to maintain.
… and cancelled.

44. SOMETIMES YOU NEED
TO BURN IT. WITH FIRE.

45. BATTLING THE MONSTER

46. Technical Debt is a team-wide problem.
Everybody needs to be a part of the solution.
DON’T POINT FINGERS

47. WORK TOGETHER
Code Standards
Pair Programming
Code Reviews

48. Unless something is on fire, or you’re losing money,
unreviewed code should never be merged into master.

49. STAY ACCOUNTABLE
Unit & Integration Tests
Pre-Commit Hooks
Continuous Integration

50. SELL IT TO MANAGEMENT
By allocating some project time to tackling debt, the
end result will be less error prone, easier to maintain,
and easier to add features to.

51. TIME
COST
Source: https://msdn.microsoft.com/en-us/magazine/ee819135.aspx
NOT BROKEN, WHY FIX IT?

52. SKI RENTAL PROBLEM
You’re going skiing for an unknown number of days.
!
It costs $1 a day to rent, or $10 to buy.
Source: http://en.wikipedia.org/wiki/Ski_rental_problem

53. Technical debt frustrates developers.
Frustrated developers are more likely to leave.
THERE’S ANOTHER COST
Hiring developers is hard.

54. Figure out the project tolerance and work with it.
Don’t be a perfectionist.
Some lingering technical debt is inevitable.

55. Use these arguments to justify the additional
time it takes you to do things right.

56. “Always code as if the guy who ends up
maintaining your code will be a violent
psychopath who knows where you
live.”
- Martin Golding
@

57. TO WIN THE FIGHT
PAY DOWN YOUR DEBT

58. PRIORITIZE
What causes the biggest & most frequent pain points for
developers?

59. What is the life expectancy of this project?
longer shelf life —> higher interest
SHELF LIFE

60. Just like with monetary debt, pay off the high interest
loan first.

61. If you don’t have to pay it off, you got something for
nothing.
Technical Debt can be strategic.

62. Is the single greatest tool in your toolbox.
REFACTORING

63. Systematically changing the code without changing
functionality, while improving design and readability.
WHAT IS IT?

64. Slow and steady wins the race.
REFACTORING
The end goal is to refactor, without breaking existing
functionality.

65. Replace functions and modules incrementally.
REFACTORING
Test as you go.
Tests are MANDATORY at this step.

66. How you make time for refactoring depends on the size
of your team.
MAKING TIME
(And the size of your problem)

67. Devote a week every 6 - 8 weeks.
SMALL
MEDIUM
Devote a person per week, rotate.
LARGE
Everyone devotes 10% of their time.

68. A FEW LAST TIPS

69. CODE IS FOR HUMANS
Source: http://despairsoftware.blogspot.com/2014/05/engineering-principles-software-best.html
Despite common misconception, code is not for
computers.
!
Code is for humans to read.

70. DON’T REPEAT YOURSELF
Source: http://despairsoftware.blogspot.com/2014/05/engineering-principles-software-best.html
If being DRY requires mind-bending backflips and
abstractions, stop.
(BUT)

71. THE BOY SCOUT RULE
The Boy Scouts have a rule: "Always leave the
campground cleaner than you found it."
Source: http://programmer.97things.oreilly.com/wiki/index.php/The_Boy_Scout_Rule
"Always check a module in cleaner than when you
checked it out."

72. EXPECT TO BE FRUSTRATED
The process of cleaning up days / months / years
of bad code can be analogous with untangling a ball of
yarn.
!
Don’t give up.

73. THANK YOU!
I’m Nina Zakharenko
@nnja /nnja
nnja.dev@gmail.com