A feature flag lets a team deploy code for a new feature while keeping that feature hidden until it is ready to expose. A running application evaluates the flag to decide which behavior to use; the flag can then be changed without restarting the application. This separates releasing software from deciding when customers see a feature. section 7.3.4 section 7.5
An environment variable such as FEATURE_DEBUG_ENABLED=true is a simple starting point, but it becomes awkward across services: containers must restart to reread changed ConfigMaps, and teams need conventions for flag types, defaults, and status. A shared flagging capability instead gives services a consistent way to consume flags while the platform team manages how they are stored and updated. section 7.3.4 section 7.2
In the Conference application, each service uses the OpenFeature SDK to evaluate flags, with flagd configured as the provider. Application code can retain its flag checks if the platform team changes providers. This gives product-facing teams a way to decide when deployed features become visible without making that decision part of the deployment itself. section 7.3.5 section 7.4
Listing 7.7 Feature flag definitions, including variants
"eventsEnabled": {
"state": "ENABLED",
"variants": {
"all": {
"agenda-service": true,
"notifications-service": true,
"c4p-service": true
},
"decisions-only": {
"agenda-service": false,
"notifications-service": false,
"c4p-service": true
},
"none": {
"agenda-service": false,
"notifications-service": false,
"c4p-service": false
}
},
"defaultVariant": "all"
The eventsEnabled definition has an enabled state and three variants: all enables events for three services, decisions-only enables them only for c4p-service, and none disables them for all three. Its default variant is all. section 7.3.5
Evaluate the flag in a service
A Conference service calls the OpenFeature SDK’s ObjectValue with the key eventsEnabled, an EventsEnabled default object, and an evaluation context. The returned value lets service code choose behavior according to the configured variant; changing the flag changes running-application behavior without a component restart. section 7.3.5 section 7.5
