NestJS Google Cloud Pub/Sub Messaging Extension – Event-Driven Transport for Distributed Systems

This extension allows you to use Google Cloud Pub/Sub as a message bus channel.

A Google Cloud Pub/Sub transport adapter for the NestJSTools Messaging Library, enabling scalable, event-driven and distributed architectures in NestJS applications.

Designed for:

• Google Cloud microservices
• Event-driven systems
• CQRS architectures
• Cross-language messaging
• Distributed platforms running on GCP

Documentation

• https://docs.nestjstools.com/messaging
• https://nestjstools.com

Installation

npm install @nestjstools/messaging @nestjstools/messaging-google-pubsub-extension 

or

yarn add @nestjstools/messaging @nestjstools/messaging-google-pubsub-extension

Google PubSub Integration: Messaging Configuration Example

import { Module } from '@nestjs/common';
import { MessagingModule } from '@nestjstools/messaging';
import { SendMessageHandler } from './handlers/send-message.handler';
import { MessagingGooglePubSubExtensionModule, GooglePubSubChannelConfig } from '@nestjstools/messaging-google-pubsub-extension';

@Module({
  imports: [
    MessagingGooglePubSubExtensionModule, // Importing the GooglePubSub extension module
    MessagingModule.forRoot({
      buses: [
        {
          name: 'message.bus',
          channels: ['pubsub-command'],
        },
      ],
      channels: [
        new GooglePubSubChannelConfig({
          name: 'pubsub-command',
          enableConsumer: true, // Enable if you want to consume messages
          autoCreate: true, // Auto-create queue if it doesn't exist
          credentials: { // Optional
            projectId: 'x',
          },
          topicName: 'eventTopic',
          subscriptionName: 'eventSubscriptionTopic',
        }),
      ],
      debug: true, // Optional: Enable debugging for Messaging operations
    }),
  ],
})
export class AppModule {}

Dispatch messages via bus (example)

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

@Controller()
export class AppController {
  constructor(
    @MessageBus('message.bus') private pubsubMessageBus: IMessageBus,
  ) {}

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

    return 'Message sent';
  }
}

Handler for your message

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

@MessageHandler('my_app_command.create_user')
export class CreateUserHandler implements IMessageHandler<CreateUser>{

  handle(message: CreateUser): Promise<void> {
    console.log(message);
    // TODO Logic there
  }
}

Key Features:

• Google Cloud Pub/Sub Integration Seamlessly send and receive messages using Google Cloud Pub/Sub within your NestJS application.

• Local Development Support with Emulator Supports running against the Google Pub/Sub emulator for local development and testing (via PUBSUB_EMULATOR_HOST).

• Automatic Topic and Subscription Creation Automatically creates Pub/Sub topics and subscriptions when autoCreate: true is set in the configuration.

• Named Buses & Channel Routing Supports custom-named message buses and routing of messages across multiple channels for event-driven architecture.

• Easily configure projectId, topicName, and subscriptionName for full control over Pub/Sub setup.

📨 Communicating Beyond a NestJS Application (Cross-Language Messaging)

To enable communication with a Handler from services written in other languages, follow these steps:

1. Publish a Message to the Topic

2. Include the Routing Key Header Your message must include a header attribute named messaging-routing-key. The value should correspond to the routing key defined in your NestJS message handler:

   @MessageHandler('my_app_command.create_user') // <-- Use this value as the routing key

🔧 Send additional attributes into your message

 this.pubSubMessageBus.dispatch(new RoutingMessage(new CreateUser('id'), 'my_app_command.create_user', new GooglePubSubMessageOptions({YourAttribute: 'value'})));

Configuration options

GooglePubSubChannel

GooglePubSubChannelConfig

| Property | Description | Default Value | | ---------------------- | ------------------------------------------------------------------------------------------------ | ----------------- | | name | The name of the messaging channel within your app (used for internal routing). | | | credentials | Google Cloud Pub/Sub credentials (e.g., { projectId: 'my-project' }). | | | enableConsumer | Whether to enable message consumption (i.e., subscribing and processing messages from Pub/Sub). | true | | autoCreate | Automatically create the topic and subscription if they do not exist in the Pub/Sub environment. | true | | topicName | The name of the Google Pub/Sub topic to publish messages to. | | | subscriptionName | The name of the subscription used to consume messages from the topic. | |

Real world working example with RabbitMQ & Redis - but might be helpful to understand how it works

https://github.com/nestjstools/messaging-rabbitmq-example