Azure App Configuration

This package makes it easier to communicate with Microsoft Azure App Configuration KeyValue and FeatureFlag resources.

Installation

To use this plugin, add azure_app_config to your pubspec.yaml file.

Authentication

There are two methods of authenticating Azure App Configuration:

1. (simple) Use the connection string which can be obtained from the App Configuration Dashboard under 'Access keys'. If the connection string is invalid or not specified, an ArgumentError will occur.

2. (complex) Use the factory constructor AzureAppConfig.customAuthentication() which enables you to provide a custom way of signing requests.

Example

Example 1: Creating an instance of AzureAppConfig

import 'package:azure_app_config/azure_app_config.dart';

void main() {
  // Creating an instance needs a connection String. This can be
  // obtained through the Azure Portal, under "Access Keys".
  final service = AzureAppConfig(connectionString: '<CONNECTION_STRING>');

  // Use the service instance to interact with Azure App Configuration.
  // ...
}

Example 2: Retrieving a key value from Azure App Configuration

import 'package:azure_app_config/azure_app_config.dart';

void main() async {
  const exampleKey = 'example_key';
  const exampleLabel = 'example_label';

  final service = AzureAppConfig(connectionString: '<CONNECTION_STRING>');

  // Getting a key value.
  try {
    final keyValue = await service.getKeyValue(key: exampleKey, label: exampleLabel);
    // Use the keyValue instance to retrieve any property of the key value.
    // ...
  } catch (err) {
    // Handle any exceptions that might occur when interacting with the Azure
    // service.
  }
}

Example 3: Retrieving a feature flag from Azure App Configuration

import 'dart:developer' as developer;

import 'package:azure_app_config/azure_app_config.dart';

void main() async {
  const exampleKey = 'example_key';
  const exampleLabel = 'example_label';

  final service = AzureAppConfig(connectionString: '<CONNECTION_STRING>');
  
  final keyValue = await service.getKeyValue(key: exampleKey, label: exampleLabel);

  // If the KeyValue is a FeatureFlag, you can use .asFeatureFlag()
  // to get the properties of the FeatureFlag
  final featureFlag = keyValue.asFeatureFlag();

  // .asFeatureFlag() will return null if it's unable to parse.
  if (featureFlag != null) {
    // To check if the featureflag is enabled, use
    developer.log('${featureFlag.enabled}');
  }
} 

Example 4: Retrieving a feature flag with feature filters from Azure App Configuration

import 'dart:developer' as developer;

import 'package:azure_app_config/azure_app_config.dart';

void main() async {
  const exampleKey = 'example_key';
  const exampleLabel = 'example_label';

  final service = AzureAppConfig(connectionString: '<CONNECTION_STRING>');

  // Register a FeatureFilter before using it.
  service.registerFeatureFilter(
    FeatureFilter.targeting(
      user: 'test.user@company.com',
    ),
  );
  
  try {
    // getFeatureEnabled() will take the feature filters into account when evaluating. 
    final isFeatureEnabled = await service.getFeatureEnabled(key: exampleKey, label: exampleLabel);

    developer.log('$isFeatureEnabled');
  } catch (err) {
    // Handle any exceptions that might occur when interacting with the Azure
    // service.
  }
}

Example 5: Finding key values based on a key and label filter

import 'dart:developer' as developer;

import 'package:azure_app_config/azure_app_config.dart';

void main() async {
  final service = AzureAppConfig(connectionString: '<CONNECTION_STRING>');

  try {
    // Find key values based on a key and label filter.
    // This example searches for the keyValues that start with '.appconfig.'
    // without a label.
    final keyValues = await service.findKeyValuesBy(
      key: '.appconfig.*',
      label: AzureFilters.noLabel,
    );

    // Loop through the values.
    for (final keyValue in keyValues) {
      developer.log(keyValue.value);
      // Use the keyValue instance to retrieve any property of the key value.
      // ...
    }
  } on AzureFilterValidationException catch (e) {
    // When an invalid filter has been provided, for example, '.appconfig.**',
    // an [AzureFilterValidationException] is thrown.
    developer.log(e.errorResponse.detail ?? 'Error occurred!');
  } catch (err) {
    // Handle any exceptions that might occur when interacting with the Azure
    // service.
  }
}

Complex Types

You are able to register types with their associated encode and decode functions. After registering the types, the library will automatically use those functions to retrieve/set values in the database.

class TimeRange {
    String start;
    String end;
    TimeRange(this.start, this.end);
    factory TimeRange.fromJson(Map<String, dynamic>)
    Map<String, dynamic> toMap() => {'start': start, 'end': end}
}

...

// Register a type, so that the library knows how to encode and decode the model
service.registerType<TimeRange>(
  decode: (jsonData) => TimeRange.fromJson(jsonData),
  encode: (timeRange) => timeRange.toMap(),
);

// Uses the passed-in [encode] method to know the json structure to use.
await service.setTyped(
    TimeRange('Monday', 'Friday'),
    key: 'time_range',
    label: 'some_label',
);

// Uses the passed-in [decode] method to know how to serialize [TimeRange]
final timeRange = await service.getTyped<TimeRange>(
    key: 'time_range',
    label: 'some_label',
); 

---

FeatureFilters

This package currently has 2 built-in FeatureFilters based on the defaults which can be found in the App Configuration dashboard:

Microsoft.Targeting -> Enable a flag based on some Targeting parameters which can be found in the Azure dashboard.

Microsoft.TimeWindow -> Enable a feature flag during a specified window of time.

Make sure to register the FeatureFilter before retrieving a feature's value.
service.registerFeatureFilter(FeatureFilter.timeWindow()) or
service.registerFeatureFilter(FeatureFilter.targeting()).

Implement your own FeatureFilter

This package enables you to create custom FeatureFilters by extending the FeatureFilter class. An example of this can be found by looking at how the built-in FeatureFilters are implemented here.

More Information

For more information about Azure App Configuration, take a look at the following resources.

• Azure App Configuration Overview
• Feature Management Overview

Feel free to submit any pull requests!