[rabbitmq-discuss] Strange subtract_acks crash in RabbitMQ 3.1.0-1 (case_clause empty) on EC2

Matthias Radestock matthias at rabbitmq.com
Sun May 19 22:56:03 BST 2013


On 18/05/13 04:20, Karl Rieb wrote:
> I am running a RabbitMQ cluster of 4 nodes in AWS EC2 on *c1.xlarge
> *instances using Ubuntu 12.04 LTS (kernel 3.2.0-38).  Periodically two
> of my nodes holding the largest queues will crash and require me to
> restart the rabbitmq-server service. [...]
>          exception exit: {{case_clause,{empty,{[],[]}}},
>                           [{rabbit_amqqueue_process,subtract_acks,3,[]},
>                            {rabbit_amqqueue_process,subtract_acks,4,[]},
>                            {rabbit_amqqueue_process,handle_cast,2,[]},
>                            {gen_server2,handle_msg,2,[]},

That's a bug in rabbit. And because it happens in a queue the queue will 

Getting past that shouldn't require a restart of rabbit though.

To help us track down the cause of the bug, it would be good to know 
whether your applications use AMQP transactions.

> There are no strange CPU spikes on my EC2 node based on AWS monitoring.

That is almost certainly an unrelated problem.


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