Azure App Configuration Provider

What is Azure App Configuration?

Azure App Configuration is a managed service that provides a central place to manage application settings and feature flags. Its feature management capabilities support simple on/off toggles as well as advanced scenarios such as targeting, time windows, percentage rollouts, and variant feature flags.

This provider lets OpenFeature applications resolve feature flags stored in Azure App Configuration. Under the hood it uses the official @azure/app-configuration-provider to load and refresh feature flags, and @microsoft/feature-management to evaluate them.

Installation

$ npm install @openfeature/azure-app-configuration-provider @azure/identity

@openfeature/server-sdk and @azure/identity are peer dependencies. Install @azure/identity if you authenticate with a token credential (recommended). It is not required when authenticating with a connection string.

Usage

The provider is a server-side provider. Register it with OpenFeature and wait for it to become ready.

Using a Microsoft Entra ID token credential (recommended)

import { OpenFeature } from '@openfeature/server-sdk';
import { AzureAppConfigurationProvider } from '@openfeature/azure-app-configuration-provider';
import { DefaultAzureCredential } from '@azure/identity';

const provider = new AzureAppConfigurationProvider({
  endpoint: 'https://<your-store>.azconfig.io',
  credential: new DefaultAzureCredential(),
});

await OpenFeature.setProviderAndWait(provider);

const client = OpenFeature.getClient();
const isEnabled = await client.getBooleanValue('Beta', false);

Using a connection string

import { OpenFeature } from '@openfeature/server-sdk';
import { AzureAppConfigurationProvider } from '@openfeature/azure-app-configuration-provider';

const provider = new AzureAppConfigurationProvider({
  connectionString: process.env.AZURE_APPCONFIG_CONNECTION_STRING!,
});

await OpenFeature.setProviderAndWait(provider);

Configuration

Provide exactly one of connectionString or endpoint + credential.

| Property | Type | Description | Default | | --------------------- | ------------------- | --------------------------------------------------------------------------------------------------------------- | ---------------------- | | connectionString | string | Connection string for the Azure App Configuration store. Mutually exclusive with endpoint/credential. | — | | endpoint | string | Endpoint URL of the Azure App Configuration store. Requires credential. | — | | credential | TokenCredential | Token credential (e.g. DefaultAzureCredential) used with endpoint. | — | | selectors | SettingSelector[] | Feature flag selectors (keyFilter, labelFilter, ...) used to filter which feature flags are loaded. | [{ keyFilter: '*' }] | | enableRefresh | boolean | Whether to periodically refresh feature flags and emit ConfigurationChanged events when a change is detected. | true | | refreshIntervalInMs | number | Polling interval (in milliseconds) used to refresh feature flags. Must be greater than 1000. | 30000 |

Flag resolution semantics

Azure App Configuration feature flags map onto OpenFeature evaluation methods as follows:

• Boolean (getBooleanValue): resolves the feature flag's enabled state via FeatureManager.isEnabled. This honors any configured feature filters (targeting, time window, percentage rollout, etc.).
• String / Number / Object (getStringValue, getNumberValue, getObjectValue): resolve variant feature flags via FeatureManager.getVariant. The variant's configuration value is returned, and the variant name is exposed as the resolution variant. If no variant is assigned, the provided default value is returned with reason DEFAULT. A TypeMismatchError is raised if the variant configuration does not match the requested type.

Targeting context

The OpenFeature evaluation context is mapped to the Azure feature-management targeting context:

• targetingKey maps to userId.
• a groups attribute (array of strings) maps to groups.

const variant = await client.getStringValue('Greeting', 'Hello', {
  targetingKey: 'user-123',
  groups: ['beta-testers'],
});

Events

When enableRefresh is true, the provider polls Azure App Configuration on refreshIntervalInMs and emits ProviderEvents.ConfigurationChanged whenever a refresh detects a change to the selected feature flags.

Building

Run nx package azure-app-configuration to build the library.

Running unit tests

Run nx test azure-app-configuration to execute the unit tests via Jest.