Celery with Redis: tasks run twice (visibility_timeout) Redis Origin: Data OSI layer 7 · Application Last updated 5 Nov 2026

Celery: Task executed twice / Restoring unacked messages — Redis broker visibility_timeout shorter than task ETA

Celery's Redis transport redelivers a task if it isn't acknowledged within visibility_timeout (1 hour by default).

Exact message you may see Celery tasks run twice Redis visibility_timeoutRestoring 1 unacknowledged message(s) Celery RedisCelery task executed twice with Redis brokervisibility_timeout Celery Redis ETA task duplicatedCelery duplicate task execution redis
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Seen on: Redis Python

Meaning

Tasks with ETA/countdown or runtime longer than visibility_timeout get redelivered, so they run again. Set broker_transport_options = {"visibility_timeout": 43200} larger than the longest ETA/runtime, make tasks idempotent, and use acks_late consciously.

Common causes

  • ETA/countdown longer than visibility_timeout
  • Long-running tasks with acks_late=True
  • Worker restarts with unacked tasks
  • Short visibility_timeout configured
  • Multiple brokers/DBs mixing

⚡ Quick fix

  1. app.conf.broker_transport_options = {"visibility_timeout": 43200}
  2. Make tasks idempotent
  3. Avoid very long ETAs; use a scheduler (beat)

Detailed fix by platform

Python

  1. app.conf.broker_transport_options = {"visibility_timeout": 3600 * 12}

How to diagnose

  1. ETA — Longer than timeout?
  2. Runtime — Task duration?
  3. Idempotent — Safe to rerun?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Data. Errors that are often confused with or caused by this one (click to open):

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