[rabbitmq-discuss] Consumer get blocked after all connections exhausted.

Fri May 16 12:46:12 BST 2014

Congratulations, you've found a bug.

The way it's meant to work is that we ensure 
file-descriptors-used-for-sockets never exceeds a certain ratio of the 
total number of file descriptors, to make sure that we always have some 
left over for file operations.

But there are some file operations (particularly around creating and 
deleting queues) which are counted as if they were sockets. So they 
block immediately when you hit the socket limit. They will tend to 
unblock as soon as you bounce off the socket limit, but if you stay 
stuck hard *at* the limit then they will not unblock.

This has been wrong since 2.7.0, and will be fixed in 3.3.2 I guess.

Cheers, Simon

On 16/05/14 02:42, Timon Wang wrote:
> It seems that Consumer will get blocked after all connections exhausted.
> Some rabbitmqctl commands such as `rabbitmqctl list_queues` and
> `rabbitmqctl list_consumers` will get stucked as well.
>
> Here is an example to demonstrate that:
> https://gist.github.com/timonwong/238f2379d1acbbd4ef0a
> After all connections are exhausted, consumer will get blocked after
> several seconds, `rabbitmqadmin list queues` will indicate that there
> was unacknowledged messages in the queue:
>
> +-------+-----------+-------------+----------------------+-----------+---------+------------------------+----------+----------+----------------+-------------------------+------------------+--------+---------+
> | vhost |   name    | auto_delete | consumer_utilisation | consumers |
> durable | exclusive_consumer_tag |  memory  | messages | messages_ready
> | messages_unacknowledged |       node       | policy |  state  |
> +-------+-----------+-------------+----------------------+-----------+---------+------------------------+----------+----------+----------------+-------------------------+------------------+--------+---------+
> | /     | test.msgs | False       | 0.105861902008       | 1         |
> True    |                        | 74966600 | 46906    | 45664
>   | 1242                    | rabbit at localhost |        | running |
> +-------+-----------+-------------+----------------------+-----------+---------+------------------------+----------+----------+----------------+-------------------------+------------------+--------+---------+
>
>
> I've tried Python kombu library with both pyamqp and librabbitmq as
> transport driver.
>
> Am I doing something wrong? Or is it a expected behavior?
>
> My environment
>
> Server side:
> CentOS 6.3 64bit
> RabbitMQ: 3.3.1
>
> Client side:
> CentOS 6.3 64bit
> Python 2.7.6
> Kombu 3.0.16
>
> Thanks in advance.
>
> Regards,
> Timon
>
>
>
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>

-- 
Simon MacMullen
RabbitMQ, Pivotal