Tech Talk @ Vingle. Devops in Startup Session 3. 1. Problems before Feature Flag 2. Benefits 3. Weak Points 4. Libraries Video: https://youtu.be/zGLRRLNYIHQ?list=PLSCpJ7HW2h8YS65XHVVVHsmav3T-g7kho

1. Feature Flag
Roll Out & Roll Back without Deployment

2. Feature Flag?
New Feature On/Off

3. Index
1. Problems before Feature Flag
2. Benefits
3. Weak Points
4. Libraries

4. Problems
before Feature Flag
Deployment == Roll Out

5. Deployment
before Feature
Flag

6. Problem 0.
No Test in Production

7. Test ENV != Prod ENV

8. Problem 1.
Unclear Delivery Time

9. From Click To Roll Out:
Maybe.. 30 minutes

10. Problem 2.
No Way to Dog
Fooding

11. QA => All Users

12. RollBack
before Feature
Flag

13. Problem 3.
Slow Delivery

14. From Click To Roll Out:
Maybe.. 30 minutes

15. Solution.
New Feature On/Off
to Some Users

16. One Click UI

17. Code Level
if FeatureFlag.active?('fetureFoo', user)
c = a/b
else
c = b == 0 ? 0 : a/b
end

18. Feature Flag Service
• Create if new flag is detected.
• List flags.
• Update a flag.
• Delete too old flags.

19. Infrastructure

20. After Feature Flag

21. Deployment
after Feature Flag

22. Benefit 0.
Test in Production

23. Benefit 1.
Clear & Fast Delivery
Time

24. One Click &
Real Time Roll Out

25. Benefit 2.
Easy Dog Fooding

26. QA => Internal User => All

27. Rollback
After Feature Flag

28. Benefit 3.
Fast Roll Back

29. One Click &
Real Time Roll Back

30. Unexpected Benefit 4.
Simple A/B Test

31. Weak Points
• Uncooperative Members
• Too Big Changes to Use Feature Flag
• Obsoleted Feature Flags are Debts
• Dependency on Each Feature Flags

32. No feature flag can be
better
• Brand New API
• Clear & Tiny Changes
• Fixing a bug that makes something worthless

33. Weak Point 0.
Uncooperative
Members

34. Solution 0.
Code Review!
No Flag No Merge

35. Weak Point 1.
Too Big Changes
to use Feature Flag

36. Solution 1.
Apply to End Point

37. Solution 1-0. in Method
if FeatureFlag.active?('fetureFoo', user)
c = foo(1, 2)
else
c = deprecated_foo(1, 2)
end
def foo(a,b)
...
...
end
def deprecated_foo(a,b)
...
...
end

38. Solution 1-0. in Class
if FeatureFlag.active?('fetureFoo', user)
c = Foo.new(1, 2)
else
c = DeprecatedFoo.new(1, 2)
end
class Foo(a,b)
...
...
end
class DeprecatedFoo(a,b)
...
...
end

39. Solution 1-0. in HTML
# Javascript
<option
ng-show=“FeatureFlag.is_active(‘fetureFoo', user)"
value="foo1"
/>
<option
ng-hide=“FeatureFlag.is_active('fetureFoo', user)"
value="foo2"
/>
# Server Rendering
<% if FeatureFlag.active?('fetureFoo', user) %>
<option value="foo1"/>
<% else %>
<option value="foo2"/>
<% end %>

40. Weak Point 2.
Obsoleted Feature Flags are
Debts

41. Solution 2.
Clean Up in The Sprint

42. Weak Point 3.
Dependency on Each Feature
Flag
Feature Flag in Feature Flag in Feature Flag in …

43. Libraries
• rollout for Ruby
• Gutter for Python
• Togglez for java

44. Reference
• https://martinfowler.com/articles/feature-
toggles.html
• https://martinfowler.com/bliki/FeatureToggle.html
• https://msdn.microsoft.com/en-
us/magazine/dn683796
• http://apptimize.com/feature-flags-launch/

45. Q & A