Queue consumers (processors) in NestJS - Mini Project: Build & Apply

Queue Consumers (Processors) in NestJS

📖 Scenario: You are building a simple task processing system using NestJS. Tasks are added to a queue, and a consumer (processor) picks up tasks to process them one by one.This is like a restaurant kitchen where orders (tasks) come in, and a chef (consumer) prepares each order in turn.

🎯 Goal: Create a NestJS queue consumer (processor) that listens to a queue named task_queue and processes incoming tasks by logging their content.

📋 What You'll Learn

Create a queue named task_queue in the consumer service

Configure a consumer (processor) method to handle jobs from task_queue

Log the job data inside the processor method

Use NestJS Bull module patterns for queue and processor setup

💡 Why This Matters

🌍 Real World

Queue consumers are used in real applications to process background tasks like sending emails, resizing images, or processing payments without blocking the main app.

💼 Career

Understanding queue consumers is important for backend developers working with microservices, distributed systems, or any app needing reliable background task processing.

1

Set up the queue consumer service

Create a NestJS service class called TaskConsumerService and import Processor and Process decorators from @nestjs/bull. Use the @Processor('task_queue') decorator on the class.

NestJS

import { Processor, Process } from '@nestjs/bull';

// Create TaskConsumerService with @Processor('task_queue') decorator
// Your code here

Need a hint?

Use @Processor('task_queue') above the class to link it to the queue.

2

Add a processor method to handle jobs

Inside TaskConsumerService, add a method called handleTask decorated with @Process() to process jobs from the queue. The method should accept a single parameter job of type any.

NestJS

import { Processor, Process } from '@nestjs/bull';

@Processor('task_queue')
export class TaskConsumerService {
  // Add a method handleTask with @Process() decorator
  // Your code here
}

Need a hint?

The @Process() decorator marks the method as a job processor.

3

Log the job data inside the processor method

Inside the handleTask method, add a line to log the job's data property using console.log(job.data).

NestJS

import { Processor, Process } from '@nestjs/bull';

@Processor('task_queue')
export class TaskConsumerService {
  @Process()
  handleTask(job: any) {
    // Log job data here
    // Your code here
  }
}

Need a hint?

Use console.log(job.data) to see the task details when processed.

4

Export the consumer service for use in the module

Add export keyword before the TaskConsumerService class declaration to make it available for import in other parts of the application.

NestJS

import { Processor, Process } from '@nestjs/bull';

// Ensure TaskConsumerService is exported
// Your code here

Need a hint?

The class must be exported so NestJS can use it as a provider.