Bitwarden.Server.Sdk.Features 1.1.0

Bitwarden.Server.Sdk.Features

About

This package enables the use of feature flags to allow remotely toggling features. You can read more about feature management at Bitwarden by reading this ADR.

How to use

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddFeatureFlagServices();

var app = builder.Build();

app.UseRouting();

app.UseFeatureFlagChecks();

app.MapGet("/", () =>
{
    return Results.Ok("my-feature enabled!");
})
    .RequireFeature("my-feature");

app.Run();

class MyService(IFeatureService featureService)
{
    public void Run()
    {
        if (featureService.IsEnabled("my-feature"))
        {
            RunNew();
        }
        else
        {
            RunOld();
        }
    }
}

The [RequireFeature] attribute can also be placed on a controller class or individual controller actions.

Both the RequireFeature method on minimal API endpoints and the [RequireFeature] attribute require the UseFeatureFlagChecks() middleware to be registered. It needs to be after UseRouting and before UseEndpoints/Map*. If you rely on authentication information in your custom context builder then the middleware should also be registered after your authentication middleware.

Out of the box, this package binds our options object FeatureFlagOptions to the Features section of configuration. This means to enable the use of Launch Darkly you need to have Features:LaunchDarkly:SdkKey set. If no key is set then local flag values can be used through Features:FlagValues:<Key>=<Value>. This can be helpful for local development.

Features:KnownFlags must be populated with all flag keys that you wish to be returned from IFeatureService.GetAll(). If you have no need to use that method you do not need to add values to that option. IFeatureService.IsEnabled and other single feature checks should continue to work just fine without it.

Example JSON configuration:

{
  "Features": {
    "FlagValues": {
      "my-flag": true,
      "another-flag": false
    },
    "KnownFlags": ["my-flag"],
    "LaunchDarkly": {
      "SdkKey": "your-sdk-key"
    }
  }
}

Customization

Context Builder

By default the feature flag context will be for an anonymous user. This doesn't allow granular targeting of feature flag values. To enable this you can implement your own IContextBuilder and register it using services.AddContextBuilder<MyContextBuilder>(). Learn more about context configuration by reading the code docs on IContextBuilder and reading Launch Darkly's docs on context configuration.

OnFeatureCheckFailed

The response that is sent back to the client on failed feature checks will return a problem details formatted error with a 404 status code by default but this can be customized through the OnFeatureCheckFailed property on FeatureCheckOptions.