OpenFeature.Providers.Ofrep

An OpenFeature provider implementation for the OpenFeature REST Evaluation Protocol (OFREP). This provider allows you to evaluate feature flags through a REST API that follows the OFREP specification.

Features

• Full implementation of the OpenFeature REST Evaluation Protocol
• Support for all standard flag types (boolean, string, integer, double, object)

Installation

Add the package to your project:

.NET Cli

dotnet add package OpenFeature.Providers.Ofrep

Basic Usage

using OpenFeature;
using OpenFeature.Providers.Ofrep;
using OpenFeature.Providers.Ofrep.Configuration;

// Configure the provider
var config = new OfrepOptions("https://zconfig.company.com/");

// Create and register the provider
var provider = new OfrepProvider(config);
await Api.Instance.SetProviderAsync(provider);

// Use feature flags
var client = Api.Instance.GetClient();

// Boolean flag
var boolFlag = await client.GetBooleanValueAsync("my-flag", false);

// String flag
var stringFlag = await client.GetStringValueAsync("greeting", "Hello");

// Integer flag
var intFlag = await client.GetIntegerValueAsync("max-retries", 3);

// Double flag
var doubleFlag = await client.GetDoubleValueAsync("sample-rate", 0.1);

Advanced Configuration

// Advanced configuration
var config = new OfrepOptions("https://feature-flags.example.com")
{
    Timeout = TimeSpan.FromSeconds(10),
    Headers = new Dictionary<string, string>
    {
        ["Custom-Header"] = "value",
        ["Api-Version"] = "v1"
    }
};

// Create and register the provider
var provider = new OfrepProvider(config);
await Api.Instance.SetProviderAsync(provider);

TimeProvider Support

For testing and scenarios where you need to control time-related behavior (such as rate limiting), you can provide a custom TimeProvider:

// Using a custom TimeProvider for testing
var customTimeProvider = new FakeTimeProvider(); // From Microsoft.Extensions.TimeProvider.Testing
var provider = new OfrepProvider(config, customTimeProvider);

When using dependency injection, the provider will automatically use any registered TimeProvider from the service container.

Configuration Options

The OfrepOptions class supports the following options:

• BaseUrl (required): The base URL for the OFREP API endpoint
• Timeout (optional): HTTP client timeout. The default value is 10 seconds.
• Headers (optional): Additional HTTP headers to include in requests

Environment Variable Configuration

The OFREP provider supports configuration via environment variables, enabling zero-code configuration for containerized deployments and CI/CD pipelines.

Supported Environment Variables

Usage with Environment Variables

using OpenFeature;
using OpenFeature.Providers.Ofrep;

// Create provider using environment variables (no explicit configuration needed)
var provider = new OfrepProvider();
await Api.Instance.SetProviderAsync(provider);

Or explicitly load from environment:

using OpenFeature.Providers.Ofrep.Configuration;

// Explicitly create options from environment variables
var options = OfrepOptions.FromEnvironment();
var provider = new OfrepProvider(options);

Header Format and URL Encoding

The OFREP_HEADERS environment variable uses a simple Key=Value format separated by commas.

Important parsing rules:

• Commas are always treated as header separators and cannot be included in values, even when URL-encoded (e.g., %2C will be decoded to , and treated as a separator).
• Equals signs (=) in the key are not supported. The first = separates the key from the value. Additional = characters in the value are allowed without encoding.
• URL encoding (e.g., %3D for =) is decoded before parsing, which is useful for systems that encode the entire value, but does not change the comma/equals parsing behavior.

Examples:

# Simple headers
export OFREP_HEADERS="Authorization=Bearer token123,Content-Type=application/json"

# Header value containing equals sign (e.g., base64) - no encoding needed for additional = in value
export OFREP_HEADERS="Authorization=Bearer abc123=="

# URL-encoded equals sign in the value (decoded to =, then treated as part of the value)
export OFREP_HEADERS="X-Data=key%3Dvalue"

# Multiple headers
export OFREP_HEADERS="Authorization=Bearer token,X-Api-Key=abc123"

Dependency Injection with IConfiguration

When using dependency injection, the provider can read configuration from IConfiguration, which supports environment variables via AddEnvironmentVariables():

// In Program.cs or Startup.cs
builder.Configuration.AddEnvironmentVariables();

builder.Services.AddOpenFeature(featureBuilder =>
{
    featureBuilder.AddOfrepProvider(options =>
    {
        // Options will fall back to OFREP_ENDPOINT, OFREP_HEADERS, OFREP_TIMEOUT_MS
        // from IConfiguration (which includes environment variables)
    });
});

Configuration Precedence

When multiple configuration sources are available, the following precedence order applies (highest to lowest):

1. Programmatic configuration (explicit OfrepOptions or OfrepProviderOptions values)
2. IConfiguration (when using DI, includes appsettings.json, user secrets, etc.)
3. Environment variables (direct Environment.GetEnvironmentVariable fallback)

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the MIT License - see the LICENSE file for details.