OpenFeature integration

Requires WestyxNexus.OpenFeature v0.10.0 or later alongside WestyxNexus.

The WestyxNexus.OpenFeature package provides NexusProvider, an OpenFeature-compliant FeatureProvider that wraps an existing NexusClient. All evaluations are served from the client’s local in-memory cache - no extra network calls are made per flag evaluation.

Installation

dotnet add package WestyxNexus.OpenFeature

Both WestyxNexus and WestyxNexus.OpenFeature must be installed. They are separate NuGet packages from the same GitLab registry.

Quick start

using OpenFeature;
using Westyx.Nexus;
using Westyx.Nexus.OpenFeature;

// Create and start the Nexus client as usual.
await using var nexus = await NexusClient.CreateAsync(new NexusConfig
{
    BaseUrl = "https://blue-ocean-a5rx7.westyx.dev",
    ApiKey  = "wxs_...",
});
nexus.ConnectStream();   // recommended - keeps flags up to date over SSE

// Register the provider once, at startup.
await Api.Instance.SetProviderAsync(new NexusProvider(nexus));

// Evaluate flags anywhere via the OpenFeature client.
var client = Api.Instance.GetClient();
bool enabled = await client.GetBooleanValue("new.checkout", false);

Value mapping

OpenFeature type	OpenFeature method	Nexus source
Boolean	`GetBooleanValue`	`GetFlag(key, defaultValue)` - returns `is_active`
String	`GetStringValue`	`GetConfig(key)` - JSON string value
Double	`GetDoubleValue`	`GetConfig(key)` - JSON number value
Integer	`GetIntegerValue`	`GetConfig(key)` - JSON integer value
Structure	`GetObjectValue`	`GetConfig(key)` - any JSON value

Flags vs configs: Boolean resolution uses GetFlag (the feature flag cache). All other types use GetConfig (the config cache).

Error handling

Scenario	`ErrorType`	`Reason`
Flag/config key not found	`FlagNotFound`	`Default` (default value returned)
Config value has wrong JSON type	`TypeMismatch`	`Error` (default value returned)
Successful evaluation	`None`	`Cached`

The provider never throws; it always returns a ResolutionDetails<T> with the appropriate error type set.

ASP.NET Core DI example

using OpenFeature;
using Westyx.Nexus;
using Westyx.Nexus.OpenFeature;

var builder = WebApplication.CreateBuilder(args);

// Register the Nexus client.
builder.Services.AddSingleton(sp =>
{
    var nexus = NexusClient.CreateAsync(new NexusConfig
    {
        BaseUrl = builder.Configuration["Nexus:BaseUrl"]!,
        ApiKey  = builder.Configuration["Nexus:ApiKey"]!,
    }).GetAwaiter().GetResult();
    nexus.ConnectStream();
    return nexus;
});

// Register the OpenFeature provider.
builder.Services.AddSingleton<NexusProvider>(sp =>
    new NexusProvider(sp.GetRequiredService<NexusClient>()));

// Register IFeatureClient for injection into services.
builder.Services.AddSingleton<IFeatureClient>(sp =>
{
    var provider = sp.GetRequiredService<NexusProvider>();
    Api.Instance.SetProviderAsync(provider).GetAwaiter().GetResult();
    return Api.Instance.GetClient();
});

Inject IFeatureClient into your services:

public class CheckoutService(IFeatureClient flags)
{
    public async Task<bool> IsNewCheckoutEnabled()
        => await flags.GetBooleanValue("new.checkout", false);
}

Live updates

When nexus.ConnectStream() is active, the client’s cache is updated within milliseconds of a remote flag change via SSE. OpenFeature evaluations pick up the new value on the next call because the provider reads directly from the live cache.

Overview

Backend SDKs

Browser SDKs

OpenFeature Providers

OpenFeature integration

Installation

Quick start

Value mapping

Error handling

ASP.NET Core DI example

Live updates

​Installation

​Quick start

​Value mapping

​Error handling

​ASP.NET Core DI example

​Live updates

Installation

Quick start

Value mapping

Error handling

ASP.NET Core DI example

Live updates