Service Discovery Package

A simple, in-memory service registry for microservices. Perfect for development and small deployments.

Features

• ✅ Service registration
• ✅ Automatic health checks (heartbeat)
• ✅ Service discovery
• ✅ Load balancing (round-robin)
• ✅ Automatic cleanup of unhealthy instances
• ✅ Easy NestJS integration

Quick Start

1. Install and Build

cd packages/service-discovery
npm install
npm run build

2. Use in Your Service

import { Module } from '@nestjs/common';
import { ServiceDiscoveryModule } from '@audit-hub/service-discovery';

@Module({
  imports: [ServiceDiscoveryModule],
})
export class AppModule {}

3. Register Your Service

import { Injectable, OnModuleInit, OnModuleDestroy } from '@nestjs/common';
import { ServiceDiscoveryClientImpl } from '@audit-hub/service-discovery';

@Injectable()
export class MyService implements OnModuleInit, OnModuleDestroy {
  private instanceId: string | null = null;

  constructor(private readonly discoveryClient: ServiceDiscoveryClientImpl) {}

  async onModuleInit() {
    // Register this service when it starts
    this.instanceId = await this.discoveryClient.registerService('my-service', 3000, 'http');
    console.log(`Service registered: ${this.instanceId}`);
  }

  async onModuleDestroy() {
    // Deregister when shutting down
    if (this.instanceId) {
      await this.discoveryClient.deregisterService(this.instanceId);
    }
  }
}

4. Discover Other Services

// Get URL of another service
const authUrl = await this.discoveryClient.getServiceUrl('auth-service', 'http');

// Get all instances
const instances = await this.discoveryClient.getServiceInstances('auth-service');

How It Works

1. Registration: Service registers itself when it starts
2. Heartbeat: Service sends heartbeat every 10 seconds
3. Discovery: Other services can find it by name
4. Cleanup: Unhealthy services are automatically removed

Production Note

For production, replace InMemoryServiceRegistry with:

• Consul
• Eureka
• Kubernetes DNS
• etcd

The interface stays the same, just swap the implementation!