Confidence SDK for Android

This is the Android SDK for Confidence, a feature flagging and Experimentation system developed by Spotify.

It also contains the Confidence OpenFeature Provider, to be used in conjunction with the Open Feature SDK.

For documentation related to flag management and event tracking in Confidence, refer to Confidence decumentation website.

Functionalities:

• Managed integration with the Confidence backend
• Prefetch and cache flag evaluations, for fast value reads even when the application is offline
• Automatic data collection about which flags have been accessed by the application
• Event tracking for instrumenting your application

Usage

Adding the package dependency

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

Add the following dependency to your gradle file to use it:

implementation("com.spotify.confidence:confidence-sdk-android:0.3.5")

Where 0.3.5 is the most recent version of this SDK.

Released versions can be found under "Releases" within this repository.

Creating the Confidence instance

You can create your Confidence instance using the ConfidenceFactory class like this:

val confidence = ConfidenceFactory.create(
    context = app.applicationContext,
    clientSecret = "<MY_SECRET>",
    region = ConfidenceRegion.EUROPE,
    loggingLevel = LoggingLevel.VERBOSE
)

Where MY_SECRET is an API key that can be generated in the Confidence UI. The loggingLevel sets the verbosity level for logging to console. This can be useful while testing your integration with the Confidence SDK.

Note: the Confidence SDK has been intended to work as a single instance in your Application. Creating multiple instances in the same runtime could lead to unexpected behaviours.

Initialization strategy

confidence.fetchAndActivate() is an async function that fetches the flags from the Confidence backend, stores the result on disk, and make the same data ready for the Application to be consumed.

The alternative option is to call confidence.activate(): this loads previously fetched flags data from storage and makes that available for the Application to consume right away. To avoid waiting on backend calls when the Application starts, the suggested approach is to call confidence.activate() and then trigger a background refresh via confidence.asyncFetch() for future sessions.

Setting the context

The context is a key-value map that will be used for sampling and for targeting input in assigning feature flag values by the Confidence backend. It is also a crucial way to create dimensions for metrics generated by event data.

The Confidence SDK supports multiple ways to set the Context. Some of them are mutating the current context of the Confidence instance, others are returning a new instance with the context changes applied.

confidence.putContext("key", ConfidenceValue.String("value")) // this will mutate the context of the current Confidence instance

val otherConfidenceInstance = confidence.withContext("key", ConfidenceValue.String("value")) // this will return a new Confidence instance with the context changes applied but the context of the original instance is kept intact

Resolving flags

Once the flags are fetched and activated, you can access their value using the getValue method or the getFlag method. Both methods uses generics to return a type defined by the default value type.

The method getFlag returns an Evaluation object that contains the value of the flag, the reason for the value returned, and the variant selected.

In the case of an error, the default value will be returned and the Evaluation contains information about the error.

The method getValue will simply return the assigned value or the default.

val message: String = confidence.getValue("flag-name.message", "default message")
val messageFlag: Evaluation<String> = confidence.getFlag("flag-name.message", "default message")

val messageValue = messageFlag.value
// message and messageValue are the same

Tracking an event

Events are defined by a name and a message where the message is a key-value map of type <String, ConfidenceValue>. You can track an event using the track method.

All context data set on the Confidence instance will be appended to the event and its message.

confidence.track("button-tapped", mapOf("button_id" to ConfidenceValue.String("purchase_button")))

The Confidence SDK has support for EventProducer. This is a way to programmatically emit context changes and events into streams which can be consumed by the SDK to automatically emit events or to automatically update context data.

The Confidence SDK comes with a pre-defined event producer to emit some application lifecycle events: AndroidLifecycleEventProducer. To use it:

import com.spotify.confidence.AndroidLifecycleEventProducer
confidence.track(
    AndroidLifecycleEventProducer(
        application = getApplication(),
        trackActivities = false // or true
    )
)

Logging

By default, the Confidence SDK will log errors and warnings. You can change the preferred log level by passing a loggingLevel to the Confidence.create() function.

To turn off logging completely, you can pass LoggingLevel.NONE to the Confidence.create() function.

OpenFeature Kotlin Confidence Provider

If you want to use OpenFeature, an OpenFeature Provider for the OpenFeature SDK is also available.

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:0.3.5")

Where 0.3.5 is the most recent version of the Provider. Released versions can be found under "Releases" within this repository.