@contentstack/message-broker v1.0.0-alpha.1

Overview

Delayed Jobs Framework consists of NestJS and Contentstack Message Broker (extended @nestjs/microservices).

Contentstack Message Broker supports several built-in message broker services like SQS, Firebase, SNS, RabbitMQ, and Redis. Message broker services are responsible for transmitting messages between different microservice instances. It natively supports both request-response and event-based message styles. Contentstack Message Broker abstracts the implementation details of each transporter behind a canonical interface for both request-response and event-based messaging. This makes it easy to switch from one message broker service to another -- for example to leverage the specific reliability or performance features of a particular transport layer -- without impacting your application code.

Also refer to NestJS Microservices documentation along with this.

Installation

To start building microservices, first install the required package:

$ npm i --save @nestjs/microservices @contentstack/message-broker

Getting started

Contentstack Message Broker does support subscribe and publish services as follows.

Terminology

Contentstack Message Broker is an extended service from @nestjs/microservices. Also, there is change in terminology as follows:

The Publisher class extends the ClientProxy class from the @nestjs/microservices package.

The Subscriber class extends the Server class and implements CustomTransportStrategy

from the @nestjs/microservices package.

The MessageBroker enum refers to Transport from the @nestjs/microservices package, but it supports SQS, SNS (only publisher), Firebase, RabbitMQ, and Redis message brokers.

For initialization or registration of Publisher and Subscriber use following documentation.

Subscriber

To instantiate a microservice, use the createMicroservice() method of the NestFactory class and to load microservice, use the subscriber() method of the MessageBrokerFactory class.

// main.ts

import { NestFactory } from '@nestjs/core'
import { MicroserviceOptions } from '@nestjs/microservices'
import { MessageBrokerFactory, MessageBroker } from '@contentstack/message-broker'
import { AppModule } from './app.module'
 
async function bootstrap() {
  const app = await NestFactory.createMicroservice<MicroserviceOptions>(
    AppModule,
    MessageBrokerFactory.subscriber({
	    'subscriber': MessageBroker.SQS, //‘SQS/Firebase/RabbitMQ/Redis’
	    'config': {config},
	    'options': {options},
    }),
  )
  await app.listenAsync()
}
bootstrap()

To create a message handler based on the request-response paradigm use the @MessagePattern() decorator, which is imported from the @nestjs/microservices package.

//job-processor.controller.ts

import { Publisher, SubscriberContext } from '@contentstack/message-broker'
import { Controller } from '@nestjs/common'
import { Ctx, MessagePattern, Payload } from '@nestjs/microservices'
 
@Controller()
export class JobProcessorController {
  @MessagePattern(‘action’)
  process(@Payload() data: any, @Ctx() context: SubscriberContext): Promise<void> {
	//TODO: perform task
	return Promise.resolve()
  }
}

Publisher

To instantiate a microservice publisher client, the publisher() method of the MessageBrokerFactory class.

//app.module.ts

import { MessageBrokerFactory, MessageBroker } from '@contentstack/message-broker'
 
@Module({
 imports: [
   MessageBrokerFactory.publisher([{
	'name': 'DEMO_PUBLISH',
	'publisher': MessageBroker.SQS,
    'config': {config},
    'options': {options},
   }]),
   ...
 ],
 ...
})

Once the module has been imported, we can inject an instance of the Publisher configured as specified via the 'DEMO_PUBLISH' transporter options shown above, using the @Inject() decorator.

//job-publisher.controller.ts
 
import { Controller, Inject } from '@nestjs/common'
import { MessagePattern } from '@nestjs/microservices'
import { Publisher } from '@contentstack/message-broker'
 
@Controller()
export class JobPublisherController {
 
  constructor(@Inject('DEMO_PUBLISH') private publisher: Publisher) {}
 
  async notify(): Promise<void> {
    return publisher.publish({message})
  }
}

Filters

There is no change in following classes and decorators. Follow @nestjs/microservices package documentation for any given use cases.

• Exception filters
• Pipes
• Guards
• Interceptors

License

@contentstack/message-broker is MIT licensed.