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Project 12: Job Queue & Background Processing

Phase 3: Advanced Integration
Why This Project?

Some tasks are too slow to run during web requests - sending bulk emails, processing videos, generating reports. Background job queues let you handle these tasks without making users wait.

This project teaches you how to build reliable systems. Jobs need to retry when they fail, scheduled tasks need to run on time, and you need visibility into what's happening. These are production concerns.

Job queues make your application more scalable. You can add more workers to process jobs faster, and if one worker crashes, the jobs don't get lost. This architecture is used by every high-traffic application.

Why This Project?

Background jobs are essential for scalable applications. You can't make users wait for slow tasks like sending emails, processing videos, or generating reports. These need to happen in the background.

This project teaches you about job queues, which are like to-do lists for your server. Jobs get added to the queue and workers process them one by one. If a job fails, it can retry automatically.

You'll learn about scheduled tasks (like daily cleanup jobs) and how to monitor your background processing. These skills are necessary for building production-ready applications.

Overview

Build a robust system for handling long-running tasks asynchronously with job queues, retry logic, scheduled tasks, and monitoring dashboards. Essential for building scalable applications that don't block user requests.

Core Requirements

Job queue using Bull and Redis

Worker processes to execute jobs

Job status tracking (pending, processing, completed, failed)

Automatic retry with exponential backoff

Scheduled/cron jobs

Job priority levels

Monitoring dashboard showing job stats

Dead letter queue for failed jobs

Job result storage and retrieval

Learning Objectives

Implement job queues with Bull

Design fault-tolerant background processing

Handle job failures and retries

Schedule recurring tasks

Monitor queue performance

Scale workers horizontally

Example Jobs to Implement

Send bulk emails (queued batch sending)

Generate PDF reports from data

Process uploaded videos (transcode, thumbnail)

Clean up old data (scheduled daily)

Import data from CSV files

Send webhook notifications to external services

Technical Challenges

Configure Redis for queue persistence

Implement exponential backoff for retries

Handle job timeouts gracefully

Build Bull Board for monitoring

Implement job prioritization

Clean up completed jobs automatically

Handle worker crashes without losing jobs

Helpful Resources

Bull: Bull documentation for job queues with Redis. Has good examples and patterns.

Redis: Redis docs for understanding the data store behind Bull.

Cron Patterns: Look up "cron syntax" for scheduling recurring jobs.

Bull Board: Bull Board gives you a dashboard to monitor jobs.

Error Handling: Learn about exponential backoff for retrying failed jobs.

Worker Processes: Read about Node.js worker threads and child processes.

Helpful Resources

Bull: Bull queue documentation on npm. Very popular for Node.js job queues.

BullMQ: Newer version of Bull with better TypeScript support.

Redis: Bull requires Redis. Learn basic Redis setup and commands.

Cron Expressions: Search for "cron expression guide" to schedule recurring jobs.

Bull Board: Web UI for monitoring Bull queues. Makes debugging easier.

Retry Strategies: Search for "exponential backoff" to learn about smart retries.

Success Criteria

Jobs process reliably in background

Failed jobs retry automatically

Dashboard shows real-time job stats

Scheduled jobs run at correct times

Workers can be scaled independently

No jobs are lost during failures

Hint: Start with simple jobs like sending emails. Once you understand the queue flow, add more complex jobs with longer processing times. Test what happens when you kill a worker mid-job.

Submit Your Project

Once you've completed this project, submit your GitHub repository link below: