[rabbitmq-discuss] Disable Per-Connection Flow Control

Simon MacMullen simon at rabbitmq.com
Fri Oct 12 12:14:16 BST 2012

On 11/10/12 13:14, Dwayne Campbell wrote:
> Hi Guys,
> RabbitMQ now turns on flow control often even at 1.5 MB/s.  I have read
> before to increase the TCP buffer size, however I do not have access to
> increase the TCP buffer size o the machines.
> How can i disable Per-Connection Flow Control ?   Memory based  and Disk
> based control is enough for me.

Hi. You should be aware that the flow control is indicating that some 
part of the message pipeline is overloaded. If you were to turn off flow 
control it would just lead to messages backing up ahead of that part of 
the pipeline - leading to memory use ballooning very rapidly and no 
increase in throughput.

If you are sending lots of tiny messages then the routing part of the 
pipeline can be the most expensive - my workstation manages only about 
2.5MB/s with zero-length messages.

The advice about increasing the buffer size is to allow your machine to 
handle short bursts of messages, at higher rates than it can manage in a 
steady state. It won't get you a higher steady state rate.

To process messages faster on a single machine you might enable HiPE 
compilation: see http://www.rabbitmq.com/configure.html

Cheers, Simon

Simon MacMullen
RabbitMQ, VMware

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