1. Technical Debt
Elizabeth Naramore
PHPBenelux
January 28, 2011
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2. Technical Debt:
What is it?
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3. Technical Debt:
Why should we care?
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4. "Shipping first time code is like going into
debt. A little debt speeds development so
long as it is paid back promptly with a
rewrite...
The danger occurs when the debt is not
repaid. Every minute spent on non-quite-
right code counts as interest on that debt.
--Ward Cunningham, 1992
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5. "I think that there were plenty of cases
where people would rush software out
the door and learn things but never put
that learning back into the program, and
that by analogy, was borrowing money
thinking that you never had to pay it
back.... eventually all your income
goes to interest and your purchasing
power goes to zero."
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6. What is technical debt?
Code or practices
that will hinder your progress
in the future.
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7. Why should we care?
Too much technical debt
can cripple your team
or organization.
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8. You have technical debt
if you have:
lack of documentation
untested code
suppressed errors
unshared knowledge between teams or people
confusing code, inconsistencies, "workarounds"
local changes you've not committed
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9. Or, if you have:
code that doesn't follow coding standards
non-existent or improperly used version control
unstable deployment process
duplicate code blocks
individual code ownership
3rd party software that needs updated or patched
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10. Guess what?
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11. We all have it.
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12. Don't panic.
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13. Some technical debt
is ok.
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14. It might make sense if:
It lets you hit a deadline
It lets you test an experimental feature
The code is rarely touched
You are coding based on reasonable expectations
It allows you to extend startup money
Your code is at the end of the life-cycle
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15. This is also known as
prudent
technical debt.
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16. So when is
technical debt
not ok?
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17. So when is
technical debt
not ok?
All the other times.
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18. This is also known as
reckless
technical debt.
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19. Sometimes we know
we are taking shortcuts,
but we do it anyway.
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20. This is also known as
deliberate
technical debt.
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21. Sometimes we don't
know any better, or
the debt is not our fault.
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22. This debt could
come from:
inexperienced team members
changing project requirements
post-release retrospectives
rd
security patches or updates from 3 parties
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23. This is also known as
inadvertent
technical debt.
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24. 4 ways to classify
technical debt:
Prudent vs. Reckless
Deliberate vs. Inadvertent
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25. Martin Fowler's Quadrant
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26. Martin Fowler's Quadrant
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27. By minimizing
deliberate debt,
you make it easier
to handle
inadvertent debt.
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28. So now that we know
what it is,
what do we do with it?
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29. We tackle our debt
with
D.E.B.T.
(see what I did there?)
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30. Discover
Estimate
Break Down
Task & Track
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31. Discover
Where is our technical debt?
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32. Discover
Where is our technical debt?
Ask the developers on your team
Use the checklist mentioned earlier
Use software like PHPUnderControl or Sonar
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33. Discover
lack of documentation
untested code
suppressed errors
unshared knowledge between teams or people
confusing code, inconsistencies, "workarounds"
local changes you've not committed
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34. Discover
code that doesn't follow coding standards
non-existent or improperly used version control
unstable deployment process
duplicate code blocks
individual code ownership
3rd party software that needs updated or patched
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35. Discover
Where is our technical debt?
Ask the developers on your team
Use the checklist mentioned earlier
Use software like PHPUnderControl or Sonar
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36. Discover
http://phpundercontrol.org/
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37. Discover
PhpUnderControl uses:
- PHPUnit
- phpDocumentor
- PHP_CodeSniffer
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38. Discover
http://sonarsource.com
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39. Discover
Sonar uses:
- PHPUnit
- PHP_CodeSniffer
- PHPDepend
- PHPMD
- phpcpd
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40. Estimate
What will it take to pay it off?
How badly is it hurting us?
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41. Estimate
The Sonar Formula
Debt(in man days)= cost_to_fix_duplications +
cost_to_fix_violations +
cost_to_comment_public_API +
cost_to_fix_uncovered_complexity +
cost_to_bring_complexity_below_threshold +
cost_to_cut_cycles_at_package_level
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42. Estimate
The Sonar Formula
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43. Estimate
http://nemo.sonarsource.org
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44. Estimate
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45. Estimate
But how much is it costing us?
The Simple-ish Formula
Amount of the “loan” = cost to fix
“Interest Rate” = Adverse impact on development
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46. Estimate
Quantifying is hard.
OK to use other techniques to generalize
the interest rate.
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47. Estimate
Use estimation technique that works for you
Get input and buy-in from the team
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48. Break it Down
What do we do with it?
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49. Break Down
What do we do with it?
Every task breaks down into 2 categories:
1. Debts where we continue paying interest
2. Debts where we pay the principal
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50. Task and Track
How can we make it visible?
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51. Task and Track
How can we make it visible?
Add it to bug tracker, task board, etc.
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52. Paying it Off
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53. Paying it Off
Focus on higher interest rate items first
OR
Focus on small ticket items first.
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54. Paying it Off
Dedicate time for technical debt reduction.
●
Use time right after a release
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Tech debt iteration
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Time each day for tech debt
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Refactor as you go
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Use off-season time
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55. Paying it Off
Keep track of your progress.
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56. Preventing Technical Debt
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Break past habits
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Group consensus & commitment
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Teach your “children” well
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Never file for bankruptcy
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Live within your means
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Anticipate your needs
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57. A Few Words About
CHANGE
MANAGEMENT
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58. Change Management
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59. Change Management
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60. Change Management
1. Direct the Rider
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61. Change Management
2. Motivate the Elephant
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62. Change Management
3. Shape the Path
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63. Make sure to see:
PHP UnderControl:
http://phpundercontrol.org
Sonar:
http://www.sonarsource.com/
(plus tech debt plugin)
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64. http://joind.in/talk/view/2418
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65. Want to contact me?
http://naramore.net/blog
@ElizabethN
elizabeth@naramore.net
Freenode IRC: ElizabethN
THANKS!
Image used with permission from Martin Fowler
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