Feature Flag: Roll Out & Roll Back without Deployment

What is Feature Flag?

Martin Fowler said:
The basic idea is to have a configuration file that defines a bunch of toggles for various features you have pending.

Also known as feature toggle, feature switch, feature flipper, conditional feature.

Pros

• Test in Production
• Clear & Fast Delivery Time
• Easy Dog Fooding
• Fast Roll Back
• Simple A/B Test

Cons

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

No feature flag can be better

• Brand New API
• Clear & Tiny Changes
• Fixing a bug that makes something worthless

Libraries

• Feature Flags in Java: Togglz, FF4J, Fitchy, Flip
• Feature Flags in Python: Gargoyle, Gutter
• Feature Flags in .NET, C#: FeatureSwitcher, NFeature, FlipIt, FeatureToggleNET, List on NUget, FeatureBee
• Ruby on Rails: rollout, feature_flipper, flip, setler, switches, FluidFeatures
• Refer to http://enterprisedevops.org/feature-toggle-frameworks-list/