RabbitMQ dropping messages after the first one

3
votes

I'm using celery 3.0.18 with RabbitMQ 3.0.2. I have a task sent to another application by using celery.send_task, and I can see the send_task call in my logs, I can see the packets leaving the worker instance, and I can see the packets reaching the RabbitMQ instance when I call tcpflow -ce -i any port 5672, however, only the first message gets to the queue. They all have the same routing key, I tried recreating the exchange and bindings, and even a new RabbitMQ instance, and nothing seems to work. This used to work fine for months, until we had to rebuild the RabbitMQ from scratch after a crash in our AWS infrastructure. Strangely, I have the exact same setup working on other application, using the same broker and the same exchange, binding and queue, and it works perfectly there. Also, it works when I send the messages to the same exchange using the same call from a management script, running from the shell on the same instance, but it doesn't work when it's sent from the celery task in the worker process.

Any ideas on what the problem might be?

1
rabbitmqcelery
Are you sure that your application, after sending task there - don't got it as Celery worker. I suppose it will look like you describing – Rustem

1 Answers

1
votes

Eventually, I figured what's wrong, but it's not clear if this is the expected behavior, a celery bug, or a RabbitMQ bug.

What happens is that besides our application tasks, I have a custom logging handler used to send logs to a central location using RabbitMQ, using celery.send_task. This logging handler sends messages to an exchange named application.logger, with a routing key like application.logger.info, application.logger.warning, etc, and have bindings to route some logging levels to specific queues. This exchange, bindings and queues were created directly in RabbitMQ and not defined in Celery routes.

When the worker tries to send a message to this exchange and it doesn't exist, Celery would log a 404 NOT_FOUND error. After that, tasks sent to other exchanges using the same connection weren't delivered. They were sent by the worker instance, we could see the packets arriving and the RabbitMQ management screen for that connection even shows the data arriving from the client in kb/s, but no messages were delivered.