Graham Brooks - Agile East 2011

1. Technical Debt
The ‘Silent’ Application Killer
© ThoughtWorks 2011
Tuesday, 8 November 11

2. Graham Brooks
http://www.thoughtworks.com/blogs/current
http://www.grahambrooks.com/blog
@wookie870
© ThoughtWorks 2011
Tuesday, 8 November 11

3. Outline
• Definition
• Why is it important?
• Symptoms and signs
• Debt resolution strategies
Tuesday, 8 November 11

4. Technical Debt
Tuesday, 8 November 11

5. Technical Debt
Metaphor coined by Ward Cunningham to
explain the misalignment between code and
current understanding
Tuesday, 8 November 11

6. Consciously taking on debt might allow
you to get something sooner
Tuesday, 8 November 11

7. Burden
• Not paying off - borrowing without paying
it back
• Spending power goes to 0
• All your money goes into paying interest
Tuesday, 8 November 11

8. Some might see this as an excuse to write
poor code.
Never write poor code
Tuesday, 8 November 11

9. Reckless Prudent
We must ship now
We don’t
Deliberate and deal with the
have time
consequences
for design
Now we know
Inadvertent What is layering? how we should
have built it
source: http://martinfowler.com/bliki/TechnicalDebtQuadrant.html
Tuesday, 8 November 11

10. Evidence is anecdotal and based on personal
experience of many projects
Tuesday, 8 November 11

11. No debt Management
Cost of Change
Time
Tuesday, 8 November 11

12. A re-write will...
• Solve all our problems
• If we use language X
• The latest framework
• A new code generator
• A new database
• .....
Tuesday, 8 November 11

13. Cost of change
Time
Tuesday, 8 November 11

14. Teams like these get better at rewrites.
They don’t learn how to continuously
deliver value indefinitely.....
Tuesday, 8 November 11

15. No debt Management
Cost of Change
Technical Debt Managed
Time
Tuesday, 8 November 11

16. Your codebase can never be in Credit
For commercial projects technical debt is a
fact of life
You either have enough or too much
Tuesday, 8 November 11

17. Symptoms and Signs
Tuesday, 8 November 11

18. Productivity
Tuesday, 8 November 11

19. Velocity
Iteration
Tuesday, 8 November 11

20. Velocity
Iteration
Tuesday, 8 November 11

21. Velocity
Iteration
Tuesday, 8 November 11

22. Velocity
Iteration
Tuesday, 8 November 11

23. Velocity
Iteration
Tuesday, 8 November 11

24. Velocity
Iteration
Tuesday, 8 November 11

25. Tracer Stories
11Point
Point
11Point
Point
11Point
Point
11Point
Point
Velocity
7h 5h 7h 10h
Time 5-10 months
Iteration
Tuesday, 8 November 11

26. Code
Tuesday, 8 November 11

27. Code Review
Tuesday, 8 November 11

28. “You know you are working on clean code
when each routine you read turns out to be
pretty much what you expected.You can call
it beautiful code when the code also makes it
look like the language was made for the
problem”
Ward Cunningham
Clean Code by Robert C Martin
Tuesday, 8 November 11

29. http://www.osnews.com/story/19266/WTFs_m
Tuesday, 8 November 11

30. Readability is a key
Tuesday, 8 November 11

31. How often features are
used
Never
Rarely
Sometimes
45%
Often NEVER USED
Always
0 12.5 25 37.5 50
Source: Standish Group
Tuesday, 8 November 11

32. Remove Unused ‘stuff’
• Unused features
• Unused files and tools
• Unused classes
• Unused methods
• Unused lines
Tuesday, 8 November 11

33. Duplication
Direct duplication
Exact Code copies
Aggressive
Algorithmically Equivolent
Tool tip: Simian
Tuesday, 8 November 11

34. !"
#!"
$!"
%!"
&!"
'!!"
'#!"
'$!"
'%!"
0569?-**"
50-:?-**"
(>4,+@?2A"
59.-5?-**"
(;50-:?A"
01D8?F=+"
Tuesday, 8 November 11
340569?A"
0159.-5?A"
+.509?-**"
:6D+6?.="
H.5.?-**"
==01?A"
01H.5.?A"
?-*90I6-5"
>4,+@?F=+"
(?*90I6-5"
.869?-**"
(25@.LF?A"
?-*90I6-5"
:6D+6?.="
K625?-**"
5K625?-**"
509<?-**"
.869?-**"
1C+.22?A"
0++69?-**"
C+.22?-**"
0<NO?F=+"
.1.869?A"
22,01?-**"
1590+?-**"
!"##$%&!"'(%&
-4+.509?A"
01D8?F=+"
(?*90I6-5"
15?-2*90I"
Volatility
+,615?-**"
<Q4<?-**"
+,615?-**"
5K625?-**"
+,615?-**"
+,615?-**"
@,.509?-2"
+,615?-**"
590++69?A"
1,509?-**"
K625?-**"
@+69?-**"
,/.+,U69?A"
9K625?-**"
09=?962F"
C0==,5"C0415"

35. Toxicity
250 branches in a single class
Tuesday, 8 November 11

36. Clean Toxic
Volatile
Volatile requirements? !Refactor Now!
Monitor
Stable Leave alone Refactor later
Tuesday, 8 November 11

37. ures
/feat
te sts
r of O C
m be on
L
u ti
N
pl ica
Ap C
LO
Te st
Time
Tuesday, 8 November 11

38. Debt resolution
strategies
Tuesday, 8 November 11

39. Stop the Line
• Works for major changes
• Challenging to implement
• Smells of a rewrite
• Short
Tuesday, 8 November 11

40. Little and often
• Make improvement part of the process:
• “Improvement as part of every change”
• Stangler pattern
Tuesday, 8 November 11

41. It’s going to get worse
before it gets better
Desired State
Productivity
Current Situation
Cost of Change
Time
Tuesday, 8 November 11

42. Closing Thoughts
Tuesday, 8 November 11

43. First Steps
• Imagine you have joined a new team
• Run metrics
• Estimate debt
• Plan next steps
• Execute the plan
Tuesday, 8 November 11

44. Software Rusts
Things Change
New capabilities
Libraries
Frameworks
OS
Tuesday, 8 November 11

45. Every modification of a system might incur
technical debt unless it is accompanied by
some effort to bring the design into line with
the requirements.
Tuesday, 8 November 11

46. Questions?
Tuesday, 8 November 11

47. Thank You!
http://www.thoughtworks.com/blogs/current
http://www.grahambrooks.com/blog
@wookie870
gbrooks@thoughtworks.com
© ThoughtWorks 2008
Tuesday, 8 November 11