Feature toggle widely used in industry to release incomplete features and do A/B testing on features. The presentation covers pros and cons of the approach and share some tips and tricks.

1. Anand Agrawal

2. Feature branches
&
Continuous Integration

3. Feature Braches
Trunk
Developer A
Developer B

4.  Pros
 Code for new feature could not make to
production
 No fear to check-in in branch
 Cons
 Merge hell
 Fear of refactoring
 Difficult to share code across branches

5. Continuous Integration

6.  Pros
 Avoid big merges
 Each check-in is production ready
 Continuously Integrate thorough out the
progress path of the feature
 Cons
 Incomplete feature may go to production
 Fear to commit code

7. Then how to do Continuous
Integration?
Feature Toggles

8. What are toggles?

9. It’s a simple if statement

10. Feature toggle is a if
statement that hides certain
execution path

11. Types of Feature toggle
 Release toggles
 Business toggles

12. Release Toggles
 To hide incomplete feature
 Short lived
 Removed as soon as feature is ready
 Have pre-decided values across
environments (except dev)

13. Business Toggles
 To enable A / B testing
 Release feature to certain groups of
people to get early feedback
 Could be enabled or disabled on the fly

14. Testing the Toggles
 Unit Test
 Test for both conditions i.e. toggle on and off
 Integration Test
 Test with toggle states that are going live
 Test with toggle on
 With business toggles be smart about what
you want to test than try and test all
combinations

15. Tips and tricks to implement
Feature Toggle

16. In case of building new API end
point that is not public facing
No feature toggle needed

17. In case of creating new
model or table
No feature toggle needed

18. In case of adding a new column
in database and exposing it
through service
No feature toggle needed
May feature toggle validations
or provide default value

19. In case of new endpoint that is
public facing
Just feature toggle the url

20. In case of UI component
embedded in existing page
Feature toggle the view
element

21. In case of logic change like
change the way payment is
processed
Feature toggle by abstraction

22. Things to keep in mind
 Don’t try to toggle each and every line of
code. Use only where its needed.
 Keep the number of toggles under
control
 Try to create mutually exclusive toggles
 Clean up release toggles and dead code

23. Ways to implement toggles
 Config file
 Toggle manager for Admin to manage
 Cookie store
 … or whatever that makes sense

24. They are riding on the same
boat

25. Feature Toggle is second best
solution. The best solution is to
find a way to gradually
integrate, without Feature
Branches or Feature Toggles.
Martin Fowler

26. No free lunch
 Good test suite (unit and acceptance)
 Fix or Revert the breaking change
immediately
 Break down features into smaller stories
 Break down stories into smaller tech
tasks
 Think of how to take your code to
production everyday than creating
blockers

27. References
 http://martinfowler.com/bliki/FeatureToggle.html
 http://www.infoq.com/presentations/Feature-Bits
 http://blog.pluralsight.com/favor-feature-toggles-
over-feature-branches
 http://paulhammant.com/blog/branch_by_abstracti
on.html
 http://labs.spotify.com/2014/03/27/spotify-
engineering-culture-part-1/

28. Questions ?