.NET SDK - Dependency injection

Package: WestyxNexus.Extensions.DependencyInjection (v0.11.0+) AddWestyxNexus() registers the client as a singleton, wires it through IHttpClientFactory and the application’s ILoggerFactory, and performs the initial sync during host startup.

dotnet add package WestyxNexus.Extensions.DependencyInjection

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddWestyxNexus(options =>
{
    options.BaseUrl = builder.Configuration["Nexus:BaseUrl"]!;
    options.ApiKey  = builder.Configuration["Nexus:ApiKey"];
});

var app = builder.Build();

Then inject NexusClient anywhere:

public sealed class CheckoutService(NexusClient nexus)
{
    public bool NewFlowEnabled() => nexus.GetFlag("new.checkout");
}

Options

Property	Default	Notes
`BaseUrl`	(required)	The full service endpoint, e.g. `https://blue-ocean-a5rx7.westyx.dev`
`ApiKey`	-	Required unless `Wif` is enabled
`Ttl`	60 s	Cache lifetime before a background refresh
`Wif`	-	Workload Identity Federation config
`Observer`	-	`IStreamObserver` for SSE lifecycle telemetry
`SseReconnectCooldown`	`[5, 10, 20, 40, 60]`	Reconnect schedule, in minutes
`EnableStream`	`true`	Start the SSE live-update stream after initialisation

HttpClient and StreamHandler are deliberately absent. On this path the HTTP clients come from IHttpClientFactory, which is the point of using it - configure them by name instead.

Startup is asynchronous

The initial sync is a network call. A plain singleton factory would have to block:

// Do not do this. It blocks a thread-pool thread during host startup.
services.AddSingleton(sp => NexusClient.CreateAsync(cfg).GetAwaiter().GetResult());

AddWestyxNexus() instead starts the work once and awaits it in an IHostedService, so host startup stays properly asynchronous and a misconfiguration surfaces as a startup failure rather than as a failure on the first request. The hosted service is inserted at the front of the service collection, so the client is ready before any hosted service you registered can resolve it.

Customising the HTTP clients

Two named clients are registered:

Name	Used for	Timeout
`NexusHttpClientNames.Sync` (`"westyx-nexus"`)	`/v1/sync`, WIF token exchange, AB evaluation	10 s
`NexusHttpClientNames.Stream` (`"westyx-nexus-stream"`)	The long-lived SSE connection	infinite

Add your own handlers, retry policies or timeouts to either:

builder.Services.AddHttpClient(NexusHttpClientNames.Sync)
    .AddPolicyHandler(myRetryPolicy);

Handler rotation is safe for SSE

IHttpClientFactory rotates handlers every two minutes, which looks fatal for a connection that stays open for hours. It is not: the factory only stops handing an expired handler to new requests - a request already in flight keeps its handler until it completes.

Do not “fix” this with SetHandlerLifetime(Timeout.InfiniteTimeSpan). That reintroduces exactly the stale-DNS problem the factory exists to solve: a process that never recycles a connection never observes an ingress reconfiguration or a load-balancer replacement.

Secrets binding - IOptions<T> for secrets
Feature management - Nexus flags through IFeatureManager
ASP.NET Core configuration - configs through IConfiguration
Design decisions

Overview

Backend SDKs

Browser SDKs

OpenFeature Providers

.NET SDK - Dependency injection

Options

Startup is asynchronous

Customising the HTTP clients

Handler rotation is safe for SSE

Next

​Options

​Startup is asynchronous

​Customising the HTTP clients

​Handler rotation is safe for SSE

​Next

Options

Startup is asynchronous

Customising the HTTP clients

Handler rotation is safe for SSE

Next