OpenFeature Kotlin Confidence Provider

Kotlin implementation of the Confidence feature provider, to be used in conjunction with the OpenFeature SDK.

Usage

Adding the package dependency

The latest release of the Provider is available on Maven central.

Add the following dependency to your gradle file:

implementation("com.spotify.confidence:openfeature-provider-android:0.2.0")

Where 0.2.0 is the most recent version of this SDK. Released versions can be found under "Releases" within this repository.

Enabling the provider, setting the evaluation context and resolving flags

Please refer to the OpenFeature Kotlin SDK documentation for more information on OpenFeature specific APIs mentioned throughout this README (e.g. setProvider, setProviderAndWait, OpenFeature Events).

Basic usage:

coroutineScope.launch {
    OpenFeatureAPI.setProviderAndWait(
        ConfidenceFeatureProvider.create(
            applicationContext,
            "<MY_SECRET>",
            initialisationStrategy = InitialisationStrategy.ActivateAndFetchAsync
        ),
        dispatcher = Dispatchers.IO,
        initialContext = ImmutableContext(targetingKey = "myTargetingKey")
    )
    val result = client.getBooleanValue("flag.my-boolean", false)
}

Where:

• MY_SECRET is an API key that can be generated in the Confidence UI.

• initializationStrategy is set to one of these two options:

  • FetchAndActivate (default): when calling setProvider/setProviderAndWait, the Provider attemtps to refresh the cache from remote and emits the OpenFeature Event ProviderReady after such an attempt (regardless of its success)
  • ActivateAndFetchAsync: when calling setProvider/setProviderAndWait, the Provider emits the OpenFeature Event ProviderReady immediately, utilizing whatever cache was saved on disk from the previous session. After that, the Provider will try to refresh the cache on disk for the future session, without impacting the current session.

Changing context after the provider initialization

The evaluation context can be changed during the app session using setEvaluationContext(...). After calling this method the new context is set for the provider, the flags will be fetched again and the cache and storage will be updated accordingly. The event ProviderReady will be emitted once the new flags are ready to be consumed by the application (note that the selected initialization strategy property doesn't play a role in this case).

Notes:

• If a flag can't be resolved from cache, the provider does NOT automatically resort to calling remote: refreshing the cache from remote only happens when setting a new provider and/or evaluation context in the global OpenFeatureAPI
• It's advised not to perform resolves while setProvider and setEvaluationContext are running: resolves might return the default value with reason STALE during such operations. The event ProviderReady can be used to guarantee correctness.

Apply events

This Provider automatically emits apply events to the Confidence backend once a flag's property is read by the application. This allows Confidence to track who was exposed to what variant and when.

Note: the apply event is only generated for flags that are successfully evaluated (i.e. default values returned due to errors don't generate apply events). Note: the apply event reports which flag and variant was read by the application, but not which property the application has read from such variant's value.

To avoid generating redundant data, as long as the flags' data returned from the backend for a user remains unchanged, only the first time a flag's property is read will generate an apply event. This is true also across restarts of the application.

The Provider stores apply events on disk until they are emitted correctly, thus ensuring the apply data reaches the backend even if generated when there is no network available (assuming the device will ever re-connect to the network before the application is deleted by the user).