This document discusses feature-driven development and the use of feature toggles. It notes that concurrent development can lead to merge conflicts and bugs, but that feature branches and toggles can help address these issues. Feature toggles allow features to be independently activated and deactivated, and provide fallback options, helping with incremental development and release. The document recommends using short-lived feature branches, metadata to describe features, and administration interfaces to manage feature states.

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Feature Driven Development

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default branchAbout me
Hendrik Ebbers @hendrikEbbers
www.guigarage.com
JUG DortmundMastering
JavaFX 8
Controls
DataFX, AquaFX,
Vagrant-Binding

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default branchContent
features workflows feature toggles

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default branchWhat is a feature?
„play“ button
feature

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default branchWhat is a feature?
„play“ button
feature

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private single developer project
Ribbon interface
removed
„play“ button added
multi touch
support Hibernate version
changed

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structure of a complex application
Backend
Frontend / UI
Persistence

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Let’s start with the UI
trunk
button on UI

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Diff of the first commit
<form >
<input type="button" value=„play“ onclick=„rpc.play()“>
</form>
class PlayService {
!
public void play() {
throw new RuntimeException(„Not implemented!“);
}
!
}

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Commit history
button on UI
JPA classes
new media service
bugfix #235
trunk

11. @hendrikEbberswww.guigarage.com
Houston, we have a problem
button on UI
JPA classes
new media service
bugfix #235
Application can’t be released!
trunk

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Concurrent development = Concurrent problems
Jim
Bob
Martin
John
bugfix 7
new
middleware
rest
services
security
issues

13. @hendrikEbberswww.guigarage.com
Concurrent development = Concurrent problems
button on UI
JPA classes
new media service
bugfix #235
trunk
Ribbon interface
removed (50%)
Ribbon interface
removed (100%)
testcommit
refactored most
entities

14. @hendrikEbberswww.guigarage.com
Concurrent development = Concurrent problems
button on UI
JPA classes
new media service
bugfix #235
trunk
Ribbon interface
removed (50%)
Ribbon interface
removed (100%)
testcommit
refactored most
entities
Application can NEVER be released!

15. @hendrikEbberswww.guigarage.com
Using a feature branch
button on UI
JPA classes
new media service
mergebranch
develop
feature
branch

16. @hendrikEbberswww.guigarage.com
Release cycle?
Application can be released!

17. @hendrikEbberswww.guigarage.com
Concurrent development?
Application can be released!
feature 1
feature 2

18. @hendrikEbberswww.guigarage.com
Problem: merge hell
Application can be released!
merge hell
f# 1 f# 4 f# 2 f# 3 f# 5
t = 2 month

19. @hendrikEbberswww.guigarage.com
Application can be released!
hidden button
and middleware
backend
visible
button
easy
merge
easy
merge
easy
merge
Solution: Dark launching & small branches

20. @hendrikEbberswww.guigarage.com
Solution: update the feature branch
Application can be released!
merge merge merge
adding button
localization of
button title
final
button icon
!
easy merge /
pull request

21. @hendrikEbberswww.guigarage.com
Problem: changes creates bugs
Application can be released!
bugs?
Point of no return

22. @hendrikEbberswww.guigarage.com
Solution: Feature Toggles
!
if(MY_FEATURE.isActive( )) {
showPlayButton( );
} activate
feature
the feature
check

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Fallback to old implementations
!
if(NEW_PERSISTENCE.isActive( )) {
return jpaCall( );
} else {
return jdbcCall( );
}
old new

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Java APIs
JSF
Support
Spring
Support Java EE
Support
Admin
Console
Activation
Strategies
State
Repositories
User
Authentification
Java SE
Support

25. @hendrikEbberswww.guigarage.com
Java APIs
JavaFX
Support
Observer
pattern
Binding
Supports
predefined
annotations

26. @hendrikEbberswww.guigarage.com
Define Features as enum
!
@Issue(„JFX-638“)
@EnabledByDefault
NEW_PERSISTENCE,
!
@Issue(„JFX-492“)
@EnabledByDefault
TWITTER_SUPPORT,
. . .
add
metadata to
describe the
feature

27. @hendrikEbberswww.guigarage.com
Features state and activation
!
MY_FEATURE.isActive( )
always
always on
dev system
next 3 hours
for random
users
stored in db
defined in
property file

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Administration view
< >
!
http://www.my-app/administration/togglz

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Fronted support
!
<h:panelGroup rendered="#{features['PLAY_FEATURE']}">
<h:commandButton value=„play" />
</h:panelGroup>
@FXML
@HideByFeature("PLAY_FEATURE")
private Button playButton;
JavaFX
JSF

30. @hendrikEbberswww.guigarage.com
Take care of your features
FEATURE_1,
FEATURE_2,
FEATURE_3,
FEATURE_4,
FEATURE_5,
. . .
FEATURE_1462,
FEATURE_11463,
Where is my
feature???
Don’t forget
to clean up!
(once a feature is
live for a defined
period of time)

31. @hendrikEbberswww.guigarage.com
Conclusion
button &
feature toggle
backend
remove
feature toggle
use feature
toggles
clean upuse short
living
branches
describe your
features with
metadata
&
provide
feature
administration
&

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Q
&
A