Celery creates 3 queues in RabbitMQ message queue

Question

I was using celery as task queue and RabbitMQ as message queue, When pushing my tasks using the delay function to the queue. I see that there were 3 queues created in the rabbit mq. I don't understand what and why do we need these 2 extra queue. Also how do I identify onto which queue my tasks are actually getting pushed into?

Started celery :

celery -A myproject worker -l info

[tasks]
  . app1.tasks.add

[2022-06-10 06:16:14,132: INFO/MainProcess] Connected to amqp://himanshu:**@IPADDRESS/vhostcheck
[2022-06-10 06:16:14,142: INFO/MainProcess] mingle: searching for neighbors
[2022-06-10 06:16:15,165: INFO/MainProcess] mingle: all alone
[2022-06-10 06:16:15,182: WARNING/MainProcess] /etc/myprojectenv/lib/python3.8/site-packages/celery/fixups/django.py:203: UserWarning: Using settings.DEBUG leads to a memory
            leak, never use this setting in production environments!
  warnings.warn('''Using settings.DEBUG leads to a memory

[2022-06-10 06:16:15,182: INFO/MainProcess] celery@ubuntu-s-1vcpu-1gb-blr1-01 ready.
[2022-06-10 06:17:38,485: INFO/MainProcess] Task app1.tasks.add[be566921-b320-466c-b406-7a6ed7ab06e7] received
[2022-06-10 06:16:15,182: INFO/MainProcess] celery@ubuntu-s-1vcpu-1gb-blr1-01 ready.
[2022-06-10 06:17:38,485: INFO/MainProcess] Task app1.tasks.add[be566921-b320-466c-b406-7a6ed7ab06e7] received
[2022-06-10 06:19:18,544: INFO/ForkPoolWorker-1] Task app1.tasks.add[be566921-b320-466c-b406-7a6ed7ab06e7] succeeded in 100.05838803993538s: 13

SO whenever I run my celery worker I see these 3 queues being generated.

RabbitMQ Management

What are those 3 queue and what for is celery using them for?

Also since queues are basically persistent database and therefore persistent queues, so why do they get deleted when I stop my workers. I see there is only 1 queue here after I stop celery.

Answer 1

• The celery queue is there so that you can send tasks to that particular queue. Every Celery worker subscribed to this queue will be able to reserve and run tasks sent to it.
• The .pidbox queue is created by every Celery worker to support execution of remote commands.
• The celeryev queue is also created by every Celery worker and is used for monitoring. Every Celery worker will every few seconds broadcast heartbeat message for an example. These messages go to the celeryev queue.

Celery documentation does not give any details about these queues, so people had to look for answeres in the Celery/Kombu source code. Here is one example: https://github.com/celery/celery/issues/6371#issuecomment-716839203