Feature State Based Toggles

A framework to map feature toggles to feature states to environments to simply toggles in Continuous Delivery without having an opinion on your project's feature states, environments or how you map them.

All of the control. None of the headache.

About the framework

The problem with traditional feature toggles

On a typical project toggles map to boolean values that have overrides for every environment

Environment	Feature Toggle Value
default	false
dev	true
qa	true
uat	true
prod	false

Accidents can happen.

It can accidentally be disabled for one of the environments (like QA)

Environment	Actual Value	Expected Value
default	false	false
dev	true	true
qa	false	true
uat	true	true
prod	false	false

Or worse, the default value can accidentally be turned on

Environment	Actual Value	Expected Value
default	true	false
dev	true	true
qa	true	true
uat	true	true
prod	true	false

Solution

The framework maps a feature toggle to a feature's state (in dev, in QA etc.). Feature states are mapped to environments (dev, QA etc.)

If a toggle is enabled on an environment, it is enabled on all environments below it.

If the feature state is in-user-acceptance-testing which maps to the uat environment (similar to the first table on top), the feature toggle will be turned on in the following environments

Environment	Toggle State
local	enabled
dev	enabled
qa	enabled
uat	enabled
prod	disabled

How to use

The entry point to the framework is FeatureTogglesForEnvironment. Sample usage is available in it's test.

// Setup
val env = new FeatureTogglesForEnvironment(fileName = "toggles.conf", baseKey = "me.karun.toggles", environmentName = "prod")

// Usage
if (env.toggleIsEnabled("feature-name")) newImplementation()
else oldImplementation()

Sample configuration is available in the test as well.

Your configuration file controls the state definitions (which map states to environments). The same configuration file also provides you the ability to map toggles to feature states (in any package structure you would like). Configure the framework based on your project's need.

Confused about what feature states you should have? Look at your story/feature development lifecycle. A sample is also available in the tests.

Confused about what environments to map to which states? Ask your self when you release software to a particular environment.

Configuration Rules

1. State Definitions are mandatory and must always be under me.karun.fsbt.stateDefinition
2. The list is order specific. Toggles mapped to states lower on the list will work on environments mapped above it.
3. If the environment value provided to FeatureTogglesForEnvironment during instantiation is not mapped to a state definition, an exception will be thrown (as shown in FeatureTogglesForEnvironmentTest)
4. If the feature toggle is mapped to a state that is not defined in the state definition, the FeatureTogglesForEnvironment instantiation will fail (as shown in FeatureTogglesForEnvironmentTest)