How we have moved from releases via Deploys to launches using Feature Flags Presentation given by Viktor Bruzhyna at Wise TechTalks

1. Launch safely with Feature Flags
Viktor Bruzhyna, software engineer at Wise Engineering
20.10.2018

2. Largest marketplace for teachers
5M users 3M products

3. What are Feature Flag?
This is a mechanism which allows to turn on/off the particular functionality
without changing the code.
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On
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4. How we have moved
from releases via Deploys
to launches using Feature Flags

5. Releasing process via deploys
● Create feature branch
● Write code
● Test on local/beta
● Fix bugs
● Resolve conflicts
● Merge
● Deploy
● Test on production
● Hotfix
● Enjoy or Rollback

6. Drawbacks of launching via deploys
● Changes have not been checked on live environment
● No real users passed through a new feature
● Deploy might cause errors spike*
● Requires extra deploy if something goes wrong
● Long lived branches

7. Long lived branches
● Maintenance is time consuming
● Plenty of merge conflicts
● Big piece of code is hidden
● Painful code reviews
● High risks of hotfixes
● High risks of rollback

8. How Feature Flags have derived?

9. Dark launching

10. Dark launching with Feature config

11. Dark launching with Feature config

12. Feature config + overriding

13. Few variants of a new feature
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14. Feature Flags framework requirements
● Ability to turn on/off without deployment
● Ability to turn on/off for particular users
● Ability to turn on/off for particular groups
● Ability to launch for percent of users
● Ability to make A/B experiments

15. Implementation

16. Our Feature Flags flow
Express + ReactJS
application
Old PHP application
Other services
Other services
Other services
Separate git repo
Feature Flags
config file
API

17. Feature Flags config file

18. Feature Flags graphQL request
Query: Response:

19. Launch a new feature
● Setup feature flag
● Get feature flag value using API
● Make conditional in code
● Deploy code darkly
● Test on production
● Launch for everybody
Feature flag value

20. Launch A/B experiment

21. A/B experiment analysis
Register button clicks
time
clicks

22. What do we get by using Feature Flags?
● Dark launching is easy
● Deploy big features by smaller parts
● Ability to test isolated code on production
● Ability to launch feature for particular users or percent of users
● Do an experiment and launch the best variant of the same feature
● Launch immediately
● Fast rollback without actual deployment

23. What do we get in addition?
● Codebase becomes more complex
● Extra work with auto tests
● Necessity to do code cleanup after launching

24. Thanks

25. Questions?