Add integration for OpenFeature/Flagd

[aj-patterson72]

.NET Aspire issue link

No response

Overview

OpenFeature is an open specification for feature flag APIs and providers.

It offers a sub-project called flagd as a default provider.

Integrating this tooling helps developers implement feature flags and control them in their local development environment while reusing feature flag definitions from their live environments.

Usage example

// Hosting
var flagd = builder.AddOpenFeature("openfeature")
    .AddFlagdProvider("flagd")
flagd.AddFile("flags.json");
flagd.AddAzureBlob("https://mystorage.blob.core.windows.net/blobs/flags.json")
flagd.WithOverride(/* Parameter */);

// Client
builder.AddOpenFeature();

public class ExampleService(IFeatureClient featureClient)
{
}

Additional context

Given OpenFeature is a client-side SDK, it may make more sense to instead define the interface as simply adding Flagd on the hosting side and instead providing a builder.AddFlagdProvider() method in the client which can be used by the existing OpenFeature SDK. However, the presence of Flagd implies the usage of OpenFeature, so it's a bit awkward to ask the user to do some of the setup on their own with OpenFeature.

Help us help you

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

[aaronpowell]

Sounds good. I assume it would be an alternative to https://www.nuget.org/packages/CommunityToolkit.Aspire.Hosting.GoFeatureFlag/ so people can choose what they'd prefer to use.

[Odonno]

Yes, do note that GoFeatureFlag also supports the OpenFeature specification. I think there is some room for a meta package called CommunityToolkit.Aspire.OpenFeature.

[aj-patterson72]

Seems sensible, I can start with a hosting package similar to the goff one and would be happy to work on a meta package on the consumer side. Admittedly I'm not sure what the API surface for such a meta package should look like. Any examples/suggestions?

[Odonno]

Naively, I'd say we add a Provider property in the resource ConnectionString

Aspire/src/CommunityToolkit.Aspire.Hosting.GoFeatureFlag/GoFeatureFlagResource.cs

Line 24 in 5b92724

public ReferenceExpression ConnectionStringExpression =>

That way, when we see Provider=goff or Provider=flagd, we can then easily setup the provider for the OpenFeature client.

The integration API should look similar to this one https://github.com/CommunityToolkit/Aspire/blob/main/src/CommunityToolkit.Aspire.GoFeatureFlag/AspireGoFeatureFlagExtensions.cs, but given a AddOpenFeatureClient extension method.

What do you think?

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[askpt]

@aaronpowell Can we reopen this issue for discussion? I would like to add the hosting integration for flagd so I can work on the #800 support.