Nats

📨 Nats Channel Integration

This extension enables seamless integration between @nestjstools/messaging and Nats.

---

🚀 Installation

Install both the core messaging package and the NATS extension:

npm install @nestjstools/messaging @nestjstools/messaging-nats-extension

or

yarn add @nestjstools/messaging @nestjstools/messaging-nats-extension

---

⚙️ Basic Setup Example

import { Module } from '@nestjs/common';
import { MessagingModule } from '@nestjstools/messaging';
import { MessagingNatsExtensionModule, NatsChannelConfig } from "@nestjstools/messaging-nats-extension";

@Module({
  imports: [
    MessagingNatsExtensionModule,
    MessagingModule.forRoot({
      buses: [
        {
          name: 'nats-event.bus',
          channels: ['nats-event'],
        },
      ],
      channels: [
        new NatsChannelConfig({
          name: 'nats-event',
          enableConsumer: true,
          connectionUris: ['nats://localhost:4222'],
          subscriberName: 'nats-core',
        }),
      ],
      debug: true,
    }),
  ],
})
export class AppModule {}

---

📬 Dispatching Messages

Use @MessageBus to inject and use the bus:

import { Controller, Get } from '@nestjs/common';
import { IMessageBus, MessageBus, RoutingMessage } from '@nestjstools/messaging';
import { CreateUser } from './application/command/create-user';

@Controller()
export class AppController {
  constructor(
    @MessageBus('nats-event.bus') private natsMessageBus: IMessageBus,
  ) {}

  @Get('/nats')
  createUser(): string {
    this.natsMessageBus.dispatch(
      new RoutingMessage(
        new CreateUser('John FROM Nats'),
        'my_app_command.create_user'
      )
    );

    return 'Message sent';
  }
}

---

🧰 Message Handler

To handle dispatched messages, use @MessageHandler:

import { MessageHandler, IMessageHandler } from '@nestjstools/messaging';
import { CreateUser } from '../create-user';

@MessageHandler('my_app_command.create_user')
export class CreateUserHandler implements IMessageHandler<CreateUser> {
  async handle(message: CreateUser): Promise<void> {
    console.log(message);
    // Implement your business logic here
  }
}

---

🔁 Cross-Language Messaging

Enable interoperability with services in other languages:

1. Publish a Message via NATS.

2. Include the Routing Header:

   messaging-routing-key: my_app_command.create_user

3. The message will be routed to the corresponding handler automatically.

---

🔄 Routing Strategy

Routing depends on the subscriberName:

• Static Routing:

  • Uses subscriberName directly as subject.

• Wildcard Routing:

  • Uses message.messageRoutingKey for dynamic routing.

subscriberName = 'order.*';
message.messageRoutingKey = 'order.created';
// Publishes to subject: 'order.created'

---

🛠️ NatsChannel Configuration Options

Property	Description	Default
name	Channel name (e.g., 'nats-event').	—
enableConsumer	Whether to consume messages from this channel.	true
connectionUris	Array of NATS server URIs (e.g., ['nats://localhost:4222']).	—
subscriberName	Queue group / subject name or pattern (e.g., 'order.*', 'my-sub').	—