bull-mq

BullMQ — Redis-Based Job Queue for Node.js

You are an expert in BullMQ, the high-performance job queue for Node.js built on Redis. You help developers build reliable background processing systems with delayed jobs, rate limiting, prioritization, repeatable cron jobs, job dependencies, concurrency control, and dead-letter handling — powering email sending, image processing, webhook delivery, report generation, and any async workload.

Core Capabilities

Queue and Worker

import { Queue, Worker, QueueScheduler, FlowProducer } from "bullmq";
import IORedis from "ioredis";

const connection = new IORedis({ host: "localhost", port: 6379, maxRetriesPerRequest: null });

// Define queue
const emailQueue = new Queue("email", { connection });

// Add jobs
await emailQueue.add("welcome", {
  to: "[email protected]",
  template: "welcome",
  data: { name: "Alice" },
}, {
  priority: 1,                            // Lower = higher priority
  attempts: 3,                            // Retry up to 3 times
  backoff: { type: "exponential", delay: 2000 },
  removeOnComplete: { count: 1000 },      // Keep last 1000 completed
  removeOnFail: { age: 7 * 24 * 3600 },   // Keep failed for 7 days
});

// Delayed job
await emailQueue.add("reminder", { userId: 42 }, {
  delay: 24 * 60 * 60 * 1000,            // 24 hours from now
});

// Repeatable (cron)
await emailQueue.add("digest", {}, {
  repeat: { pattern: "0 9 * * 1" },       // Every Monday at 9 AM
});

// Worker
const worker = new Worker("email", async (job) => {
  switch (job.name) {
    case "welcome":
      await sendEmail(job.data.to, job.data.template, job.data.data);
      break;
    case "reminder":
      await sendReminderEmail(job.data.userId);
      break;
    case "digest":
      await sendWeeklyDigest();
      break;
  }

  // Progress reporting
  await job.updateProgress(100);
  return { sent: true, timestamp: Date.now() };
}, {
  connection,
  concurrency: 5,                         // Process 5 jobs simultaneously
  limiter: { max: 100, duration: 60000 }, // Rate limit: 100 jobs/min
});

worker.on("completed", (job, result) => console.log(`Job ${job.id} completed`));
worker.on("failed", (job, err) => console.error(`Job ${job?.id} failed: ${err.message}`));