Task Queues Understanding task queues for distributed job processing.
A Task Queue is a mechanism for distributing work across multiple workers. Unlike simple message queues, task queues typically focus on job execution with features like retries, scheduling, and progress tracking.
Aspect Message Queue Task Queue Focus Message delivery Job execution Features Basic delivery Retries, scheduling, results Semantics Data transfer Work processing Examples RabbitMQ, SQS Celery, Sidekiq, Bull
Client Task Queue Workers │ │ │ │─── Submit Task ───────►│ │ │ │ │ │◄── Task ID ────────────│ │ │ │ │ │ │──── Assign Task ────►│ │ │ │ │ │◄─── Progress ────────│ │ │ │ │ │◄─── Result ──────────│ │ │ │ │◄── Poll Result ────────│ │ Feature Description Retries Automatically retry failed tasks Scheduling Run tasks at specific times Priority High-priority tasks first Rate limiting Control task execution rate Result storage Store and retrieve task results Progress tracking Monitor task completion
Use Case Example Background jobs Send emails, generate reports Scheduled tasks Daily cleanup, cron jobs Long-running tasks Video encoding, data processing Distributed computation Map-reduce operations Webhooks Process incoming webhook payloads
PENDING ──► STARTED ──► SUCCESS └──► FAILURE ──► RETRY └──► DEAD (max retries) System Language Backend Celery Python Redis, RabbitMQ Sidekiq Ruby Redis Bull Node.js Redis BullMQ Node.js Redis Hangfire .NET SQL Server, Redis
from celery import Celery app = Celery( 'tasks' , broker = 'redis://localhost:6379' ) @app.task ( bind = True , max_retries = 3 ) def process_order (self, order_id): try : # Process the order result = do_processing(order_id) return result except Exception as e: # Retry with exponential backoff raise self .retry( exc = e, countdown = 2 ** self .request.retries) # Submit task task = process_order.delay( order_id = 123 ) # Check result result = task.get( timeout = 30 )
Differentiate from simple message queues
Explain retry strategies and dead letter handling
Discuss idempotency for at-least-once delivery
Mention scheduling and priority features
Give examples: email sending, report generation
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