Add OpenFeature OFREP for feature flags support

[askpt]

.NET Aspire issue link

No response

Overview

OpenFeature provides standardisation across feature flag providers, allowing developers to switch between different systems without rewriting application code. As a CNCF project it would be a great addition to the Aspire toolset. More information here: https://openfeature.dev

I am planning on bringing support of OpenFeature using the OFREP protocol (https://www.nuget.org/packages/OpenFeature.Providers.Ofrep) and a container integration (flagd).

• OFREP: https://github.com/open-feature/protocol
• flagd: https://flagd.dev

The idea behind is dotnet aspire would be able to use locally the container (flagd) using OFREP as a communication method and in production, that endpoint would be overwritten by the production endpoint. Similar on how the OTEL and Aspire dashboard currently works.

Benefits

This integration would provide the .NET Aspire community with:

• Standardised Feature Management: Consistent API across different feature flag providers (flagd, goff or others that use the OFREP endpoint)
• Enhanced Development Workflows: Local development support with containerised services
• Future Flexibility: Easy migration between OFREP compatible providers

Components

• CommunityToolkit.Aspire.Hosting.OpenFeature.OFREP <- contains the OpenFeature.OFREP specific implementation
• CommunityToolkit.Aspire.FlagD <- contains the container for flagd (please note, we should not restrain from using other providers that also support OFREP like GoFeatureFlag)

Usage example

AppHost

var builder = DistributedApplication.CreateBuilder(args);

var flagd = builder.AddFlagd("feature-flags")
    .WithFlagConfiguration("./flags.json")
    .WithOfrepPort(8016);

var api = builder.AddProject<Projects.MyApi>("api")
    .WithReference(ofrep);

ServiceDefaults

        builder.Services.AddOpenFeature(ofBuilder =>
        {
            ofBuilder
                .AddHostedFeatureLifecycle()
                .AddOfrepProvider() // Service url should be retrieved from the configuration
                .AddHook<TraceEnricherHook>()
                .AddHook<MetricsHook>();
        });

Implementation

var service = sp.GetService<IFeatureClient>(); // This is injected. Just adding the service here to showcase
var isEnabled = await featureClient.GetBooleanValueAsync( "new-feature", false);

Additional context

This is my repository for demos: https://github.com/askpt/openfeature-aspire-welcome. This repository uses the flagD provider implementation but for this issue I will focus on the OFREP provider.

I am also a maintainer for OpenFeature .NET SDK and I will be more than happy to help in the implementation of this integration.

Help us help you

Yes, I'd like to be assigned to work on this item

[Odonno]

Isn't that a duplicate of #737?

[askpt]

Isn't that a duplicate of #737?

It is similar indeed, but there are a couple of differences between what was proposed initially and what I am proposing.

The flagd hosting is the same idea, the AppHost would need to declare flagd container.
The difference is about the OFREP as a provider instead of the flagd provider. OFREP can communicate with a lot of different providers (flagd, GoFeatureFlag, DevCycle and others I don't remember). Imagine this as the otel endpoint but for feature flags. I am happy to reopen #737 and add the container services, and dedicate this issue exclusively to OFREP.

Thanks for pointing the possible duplicate @Odonno

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[askpt]

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