[rabbitmq-discuss] RabbitMQ .NET client BasicConsume and HandleBasicDeliver question

T-zex tranzenziuzex at gmail.com
Wed Jun 15 13:35:09 BST 2011

In my case it doesn't matter if it is IModel.Close() or
IModel.ChannelFlow(false) couse the process must be terminated anyway.
We need an atomic operation which would ack the message and would not
fetch the other one. It seems that BasicConsume is unable to gurantee
that, so maybe BasicGet is a better option?

On Wed, Jun 15, 2011 at 12:03 PM, Emile Joubert <emile at rabbitmq.com> wrote:
> Hi,
> Prefetch count limits the number of unacknowledged messages, so you
> would need to acknowledge the last message to get the next one if the
> prefetch count was set to 1.
> You should never need to close the channel for flow control. You can use
> IModel.ChannelFlow() if you need to temporarily stop the broker from
> delivering messages. This works independently from the prefetch count.
> -Emile
> On 15/06/11 10:55, T-zex wrote:
>> Thank you!
>> When prefetch count is set to 1 channel will try to fetch the next
>> message as soon as HandleBasicDeliver returns? Should I invoke
>> Channel.Close() on a different thread (to avoid blocking) and then
>> return?
>> On Wed, Jun 15, 2011 at 10:33 AM, Emile Joubert <emile at rabbitmq.com> wrote:
>>> Hi,
>>> On 15/06/11 10:08, T-zex wrote:
>>>> Hi,
>>>> We are overriding DefaultBasicConsumer.HandleBasicDeliver method and
>>>> use IModel.BasicConsume to subscribe to incoming messages:
>>>> model.BasicConsume(queue, false, instanceOfDerivedConsumer);
>>>> When application fails to ack a message that message is requeued. How
>>>> can I guarantee that BasicConsume is receiving one message at a time?
>>>> How to deterministically stop consuming when application detects that
>>>> it is unable to process a message and prevent the second message from
>>>> arriving? How to make sure that there is one and only one unacked
>>>> message and that message is at the peak of broker queue.
>>> The solution is to set the prefetch count of the channel to 1 using
>>> IModel.BasicQos(). Also see
>>> http://www.rabbitmq.com/amqp-0-9-1-quickref.html#basic.qos .
>>> Note that rabbit does not implement the prefetch size or global
>>> parameters to the same method.

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