Node.js SDK - NestJS - Westyx Nexus

New in v0.11.0. @westyx-nexus/sdk-nestjs registers a single NexusClient in the Nest container, so services inject it instead of constructing one.

npm install @westyx-nexus/sdk-nestjs

It is a separate package so that a plain Node consumer does not pull @nestjs/common and @nestjs/core; @nestjs/* are optional peer dependencies here. Nest 10 and newer are supported - the module uses only stable dependency-injection primitives.

Static configuration

import { Module } from '@nestjs/common';
import { NexusModule } from '@westyx-nexus/sdk-nestjs';

@Module({
  imports: [
    NexusModule.forRoot({
      endpoint: process.env.NEXUS_ENDPOINT,
      apiKey: process.env.NEXUS_API_KEY,
      isGlobal: true,
    }),
  ],
})
export class AppModule {}

forRoot accepts everything NexusConfig accepts, plus isGlobal.

Configuration from `ConfigService`

The form real applications use, because the endpoint and key are only known once the container is up:

import { ConfigModule, ConfigService } from '@nestjs/config';

NexusModule.forRootAsync({
  imports: [ConfigModule],
  inject: [ConfigService],
  useFactory: (config: ConfigService) => ({
    endpoint: config.getOrThrow<string>('NEXUS_ENDPOINT'),
    apiKey: config.getOrThrow<string>('NEXUS_API_KEY'),
  }),
});

The factory may be async. Anything it injects has to be reachable from inside the module, which is what imports is for.

Injecting the client

import { Injectable } from '@nestjs/common';
import { NexusClient } from '@westyx-nexus/sdk-nodejs';

@Injectable()
export class PricingService {
  constructor(private readonly nexus: NexusClient) {}

  pageSize(): number {
    return Number(this.nexus.getConfig('pagination.page_size') ?? 25);
  }

  newCheckout(): boolean {
    return this.nexus.getFlag('new-checkout', false);
  }
}

NexusClient itself is the injection token, so no @Inject(...) is needed. It is a singleton: every injection site receives the same client, and therefore the same cache and the same SSE connection. isGlobal: true makes it injectable from any module without importing NexusModule there. It defaults to false, matching ConfigModule; for a single SDK client per application, true is usually what you want.

Initialisation

There is deliberately no separate OnModuleInit step. The provider factory calls NexusClient.create(), which performs the initial blocking sync and opens the stream - so a module that has finished initialising is one whose client is already populated, and no service can observe a half-ready client. A failing initial sync therefore fails application start-up, which is the behaviour a missing configuration source should have: better to refuse to boot than to serve traffic with an empty cache. A malformed option fails even earlier, before any network call.

Teardown

onModuleDestroy closes the client, which disconnects the SSE stream, cancels the refresh timer, releases the connection pools, and deletes the materialised secret files. This matters more than it looks. An SSE connection that survives module teardown keeps the process alive - Nest appears to shut down and the process does not exit - and holds a stream slot open on the server. There is a test for exactly that: after app.close(), client.streamConnected is false and no further request reaches the backend. Nothing to call yourself; enable Nest’s shutdown hooks as usual if you want signals to trigger it:

const app = await NestFactory.create(AppModule);
app.enableShutdownHooks();

Logging

Nest’s Logger is bridged into the SDK’s structured logger by default, with the context Nexus, so the SDK’s diagnostics appear in your application log with nothing configured. A structured Nest logger - nestjs-pino, for instance - receives the SDK’s fields as real fields. Pass your own logger in the options to override it.

Overview

Backend SDKs

Browser SDKs

OpenFeature Providers

Node.js SDK - NestJS

Static configuration

Configuration from `ConfigService`

Injecting the client

Initialisation

Teardown

Logging

Next

​Static configuration

​Configuration from ConfigService

​Injecting the client

​Initialisation

​Teardown

​Logging

​Next

Static configuration

Configuration from `ConfigService`

Injecting the client

Initialisation

Teardown

Logging

Next