smart-queue-nestjs

Features

• Production-Ready: Fault tolerance, retry strategies, dead-letter queues
• Observability: Structured logging, Prometheus metrics, health checks
• Type-Safe: Full TypeScript support with generics
• Scalable: Horizontal scaling with configurable concurrency
• Developer Experience: Clean decorators, async configuration

Installation

npm install smart-queue-nestjs bullmq ioredis

Quick Start

1. Configure the Module

import { Module } from '@nestjs/common';
import { SmartQueueModule } from 'smart-queue-nestjs';

@Module({
  imports: [
    SmartQueueModule.forRoot({
      connection: {
        host: 'localhost',
        port: 6379,
      },
      defaultJobOptions: {
        attempts: 3,
        backoff: {
          type: 'exponential',
          delay: 1000,
        },
      },
    }),
  ],
  exports: [SmartQueueModule],
})
export class AppModule {}

2. Create a Producer Service

import { Injectable } from '@nestjs/common';
import { QueueService } from 'smart-queue-nestjs';

interface EmailJobData {
  to: string;
  subject: string;
  body: string;
}

@Injectable()
export class EmailProducerService {
  constructor(private readonly queue: QueueService) {}

  async sendEmail(data: EmailJobData) {
    const job = await this.queue.add('emails', 'send', data, {
      attempts: 3,
      backoff: { type: 'exponential', delay: 1000 },
    });
    
    return job;
  }
}

3. Create a Consumer/Worker

import { Injectable, Logger } from '@nestjs/common';
import { QueueService } from 'smart-queue-nestjs';

interface EmailJobData {
  to: string;
  subject: string;
  body: string;
}

@Injectable()
export class EmailWorkerService {
  private readonly logger = new Logger(EmailWorkerService.name);

  constructor(private readonly queue: QueueService) {
    this.registerWorker();
  }

  private registerWorker() {
    this.queue.worker<EmailJobData>(
      'emails',
      async ({ id, data }) => {
        this.logger.log(`Processing email job ${id}`);
        
        // Send email logic here
        await this.sendEmail(data);
        
        return { success: true, jobId: id };
      },
      {
        concurrency: 5,
        retryStrategy: {
          maxAttempts: 3,
          backoff: { type: 'exponential', delay: 1000 },
        },
      },
    );
  }

  private async sendEmail(data: EmailJobData): Promise<void> {
    // Email sending implementation
  }
}

Advanced Usage

Async Configuration

import { Module } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { SmartQueueModule } from 'smart-queue-nestjs';

@Module({
  imports: [
    SmartQueueModule.forRootAsync({
      useFactory: (config: ConfigService) => ({
        connection: {
          host: config.get('REDIS_HOST'),
          port: config.get('REDIS_PORT'),
          password: config.get('REDIS_PASSWORD'),
        },
      }),
      inject: [ConfigService],
    }),
  ],
})
export class AppModule {}

Type-Safe Job Payloads

// Define your job data types
interface ProcessOrderData {
  orderId: string;
  items: Array<{ productId: string; quantity: number }>;
  customerEmail: string;
}

interface ProcessOrderResult {
  orderId: string;
  status: 'processed' | 'failed';
  processedAt: string;
}

// Producer
const job = await queue.add<OrderData>('orders', 'process', {
  orderId: 'ORD-123',
  items: [{ productId: 'PROD-1', quantity: 2 }],
  customerEmail: '[email protected]',
});

// Worker with full type safety
queue.worker<OrderData>(
  'orders',
  async ({ id, data }) => {
    const result = await processOrder(data);
    return result; // Fully typed
  },
);

Retry Strategies

// Exponential backoff (default)
this.queue.add('jobs', 'process', data, {
  attempts: 5,
  backoff: {
    type: 'exponential',
    delay: 1000, // 1s, 2s, 4s, 8s, 16s
  },
});

// Fixed delay
this.queue.add('jobs', 'process', data, {
  attempts: 3,
  backoff: {
    type: 'fixed',
    delay: 5000, // Always 5s between retries
  },
});

// Number shorthand (fixed delay in ms)
this.queue.add('jobs', 'process', data, {
  attempts: 3,
  backoff: 2000,
});

Dead Letter Queue (DLQ)

@Injectable()
export class OrderProcessorService {
  constructor(private readonly queue: QueueService) {
    this.setupQueue();
  }

  private setupQueue() {
    // Enable DLQ for failed jobs after max retries exhausted
    this.queue.registerDeadLetterQueue('orders', {
      enabled: true,
      queueName: 'orders-dlq',
      maxRetries: 3,
    });

    this.queue.worker<OrderData>(
      'orders',
      async ({ id, data }) => {
        // Process order
      },
      {
        retryStrategy: {
          maxAttempts: 3,
          backoff: { type: 'exponential', delay: 1000 },
        },
      },
    );
  }

  // Process DLQ jobs separately
  async reprocessFailedOrders() {
    const failedJobs = await this.queue.getRepeatableJobs('orders-dlq');
    // Reprocess logic
  }
}

Idempotent Job Addition

// Prevent duplicate jobs using idempotency keys
async addPaymentProcessing(orderId: string, amount: number) {
  const idempotencyKey = `payment-${orderId}-${Date.now()}`;
  
  await this.queue.addWithIdempotencyKey(
    'payments',
    'process',
    { orderId, amount },
    idempotencyKey, // Same key = same job, no duplicates
  );
}

Job Hooks

this.queue.registerJobHooks('orders', {
  beforeJob: async (jobId, data) => {
    console.log(`Starting job ${jobId}`);
    // Validation, logging, etc.
    return data;
  },
  afterJob: async (jobId, result) => {
    console.log(`Job ${jobId} completed with result:`, result);
    // Notifications, cleanup, etc.
  },
  onJobFailed: async (jobId, error) => {
    console.log(`Job ${jobId} failed:`, error.message);
    // Alerting, cleanup, etc.
  },
});

Delayed Jobs

// Execute after 5 minutes
await this.queue.delay('notifications', 'send', data, 5 * 60 * 1000);

// Schedule with cron
await this.queue.repeat('reports', 'generate', data, '0 0 * * *'); // Daily at midnight

Health Checks

@Controller('health')
export class HealthController {
  constructor(private readonly queue: QueueService) {}

  @Get('queue')
  async checkQueueHealth() {
    const health = await this.queue.checkHealth('orders');
    return {
      queue: health.queueName,
      isHealthy: health.isHealthy,
      connectionStatus: health.connectionStatus,
      jobCounts: health.jobCounts,
    };
  }

  @Get('queue/all')
  async checkAllQueues() {
    return this.queue.checkAllHealth();
  }
}

Prometheus Metrics

@Controller('metrics')
export class MetricsController {
  constructor(private readonly queue: QueueService) {}

  @Get()
  getMetrics() {
    return this.queue.getMetrics();
  }
}

Returns Prometheus-format output:

# TYPE smart_queue_jobs_created_total counter
smart_queue_jobs_created_total{queue="orders"} 150
# TYPE smart_queue_jobs_completed_total counter
smart_queue_jobs_completed_total{queue="orders"} 145
...

Configuration Options

SmartQueueConnectionOptions

| Option | Type | Default | Description | |--------|------|---------|-------------| | host | string | 'localhost' | Redis host | | port | number | 6379 | Redis port | | db | number | 0 | Redis database | | password | string | - | Redis password | | keyPrefix | string | 'smart-queue' | Key prefix | | tls.enabled | boolean | false | Enable TLS | | tls.ca | string | - | CA certificate | | tls.cert | string | - | Client certificate | | tls.key | string | - | Client key |

ProcessorOptions

| Option | Type | Default | Description | |--------|------|---------|-------------| | queue | string | - | Queue name | | concurrency | number | 1 | Concurrent jobs | | limiter.max | number | - | Rate limit max | | limiter.duration | number | - | Rate limit duration | | lockDuration | number | 30000 | Job lock duration |

Production Setup

High Availability

SmartQueueModule.forRoot({
  connection: {
    host: process.env.REDIS_HOST,
    port: parseInt(process.env.REDIS_PORT),
    password: process.env.REDIS_PASSWORD,
    // Connection pool for high load
    maxRetriesPerRequest: 3,
    enableOfflineQueue: false,
    retryStrategy: (times) => {
      if (times > 10) return null; // Stop retrying
      return Math.min(times * 200, 2000);
    },
  },
  defaultJobOptions: {
    attempts: 5,
    backoff: { type: 'exponential', delay: 1000 },
    removeOnComplete: 100,
    removeOnFail: 500,
  },
});

Graceful Shutdown

The module automatically handles graceful shutdown via onModuleDestroy:

• Pauses new job processing
• Waits for active jobs to complete
• Closes connections cleanly

For custom handling:

async onModuleDestroy() {
  // Stop accepting new jobs
  await this.queue.pause('orders');
  
  // Wait for active jobs (up to 30s)
  await this.delay(30000);
  
  // Force close
  await this.queue.close('orders');
}

API Reference

QueueService

class QueueService {
  // Job Management
  add<T>(queue, name, data, options): Promise<Job>
  addWithIdempotencyKey<T>(queue, name, data, key, options): Promise<Job>
  delay<T>(queue, name, data, delay, options): Promise<Job>
  repeat<T>(queue, name, data, cron, options): Promise<Job>
  
  // Job Queries
  getJob(queue, jobId): Promise<Job | null>
  getMetrics(queue): Promise<QueueMetrics>
  getRepeatableJobs(queue): Promise<Job[]>
  
  // Queue Control
  pause(queue): Promise<void>
  resume(queue): Promise<void>
  drain(queue): Promise<void>
  clean(queue, grace, status): Promise<string[]>
  close(queue): Promise<void>
  
  // Worker
  worker<T>(queue, processor, options): void
  on(queue, event, handler): void
  
  // Health & Metrics
  checkHealth(queue): Promise<QueueHealthCheck>
  checkAllHealth(): Promise<Map<string, QueueHealthCheck>>
  getMetrics(): string
  
  // Configuration
  registerQueue(name, options): void
  registerDeadLetterQueue(name, options): void
  registerJobHooks(name, hooks): void
}

Bull Board Dashboard (Optional)

For queue monitoring, install @bull-board/api:

npm install @bull-board/api

Then create a controller:

import { Controller, Get, Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';
import { createBullBoard } from '@bull-board/api';
import { BullAdapter } from '@bull-board/api';
import { QueueRegistry } from 'smart-queue-nestjs';

@Controller('admin/queues')
export class QueueAdminController {
  constructor(private readonly registry: QueueRegistry) {}

  @Get()
  async getDashboard() {
    const queues = this.registry.getRegisteredQueueNames()
      .map(name => this.registry.getQueue(name))
      .filter(q => q)
      .map(q => new BullAdapter(q!));

    const board = createBullBoard({ queues });
    return board.ui;
  }
}

Access at http://localhost:3000/admin/queues

Processor Auto-Discovery

Use decorators to auto-register job handlers. The ProcessorScannerService is now automatically registered as a provider:

import { Processor, QueueHandler } from 'smart-queue-nestjs';

interface OrderData {
  orderId: string;
  amount: number;
}

@Processor('orders', { concurrency: 5 })
export class OrderProcessor {
  @QueueHandler('process-order', {
    retryStrategy: {
      maxAttempts: 3,
      backoff: { type: 'exponential', delay: 1000 },
    },
  })
  async processOrder({ id, data }: { id: string; data: OrderData }) {
    console.log(`Processing order ${data.orderId}`);
    // Process order
    return { success: true };
  }

  @QueueHandler('cancel-order')
  async cancelOrder({ id, data }: { id: string; data: OrderData }) {
    console.log(`Cancelling order ${data.orderId}`);
    return { success: true };
  }
}

The scanner is automatically available when using SmartQueueModule.forRoot() - just add your processor classes to the module providers:

import { Module } from '@nestjs/common';
import { SmartQueueModule } from 'smart-queue-nestjs';

@Module({
  imports: [SmartQueueModule.forRoot({
    connection: { host: 'localhost', port: 6379 },
  })],
  providers: [OrderProcessor],
})
export class AppModule {}

Production Notes

v1.3.0 - Dependency Injection Fixes

This release fixes critical issues with dependency injection that could cause the QueueRegistry to be undefined during worker creation:

• Fixed: BullMQAdapter now uses explicit useFactory with inject to guarantee QueueRegistry is initialized before use
• Added: Defensive checks with clear error messages if registry is unavailable
• Fixed: BullBoardModule now properly injects QueueRegistry with @Optional() decorator
• Added: ProcessorScannerService is now automatically registered as a provider
• Fixed: QueueHealthService Redis client access no longer relies on unsafe any casts

Fail-Fast Error Messages

The library now throws clear, actionable errors:

QueueRegistry is not available. Ensure SmartQueueModule.forRoot() is called before using queues.

QueueRegistry is not initialized. Ensure SmartQueueModule.forRoot() has been called and the module has been initialized before creating workers.

License:

MIT