Why do my RabbitMQ channels keep closing?

Another reason in my case was that by mistake I acknowledged a message twice. This lead to RabbitMQ errors in the log like this after the second acknowledgment.

=ERROR REPORT==== 11-Dec-2012::09:48:29 ===
connection <0.6792.0>, channel 1 - error:
{amqp_error,precondition_failed,"unknown delivery tag 1",'basic.ack'}

After I removed the duplicate acknowledgement then the errors went away and the channel did not close anymore and also the AlreadyClosedException were gone.

I'd like to add this information for other users who will be searching for this topic

Another possible reason for Receiving a Channel Closed Exception is when Publishers and Consumers are accessing Channel/Queue with different queue declaration/settings

Publisher

channel.queueDeclare("task_queue", durable, false, false, null);

Worker

channel.queueDeclare("task_queue", false, false, false, null);

From RabbitMQ Site

RabbitMQ doesn't allow you to redefine an existing queue with different parameters and will return an error to any program that tries to do that

An AMQP channel is closed on a channel error. Two common things that can cause a channel error:

• Trying to publish a message to an exchange that doesn't exist
• Trying to publish a message with the immediate flag set that doesn't have a queue with an active consumer set

I would look into setting up a ShutdownListener on the channel you're trying to use to publish a message using the addShutdownListener() to catch the shutdown event and look at what caused it.

Apparently, there are many reasons for the AMQP connection and/or channels to close abruptly. In my case, there was too many unacknowledged messages on the queue because the consumer didn't specify the prefetch_count so the connection was getting terminated every ~1min. Limiting the number of unacknowledged messages by setting the consumer's prefetch count to a non-zero value fixed the problem.

channel.basicQos(100);