[rabbitmq-discuss] Per Connection Flow Control Issue

Simon MacMullen simon at rabbitmq.com
Fri Oct 26 13:41:24 BST 2012

On 26/10/12 11:23, Brendan Hay wrote:
> Yes, so what should the expected observation be - the client code
> carries on publishing into a black hole,
> which means the send queue on the client/peer socket should keep
> growing,

Well, the send queue is limited in size. So the publisher should block 
fairly quickly.

> and when the rabbit reader is
> issued new credits, it will lap it all up?


> It just seems the 'flow' status in the UI stays on permanently, it
> doesn't seem to be toggling at high speed, just locked.

Well, the flow status *in the UI* is designed not to toggle at high 
speed, since that would not be very readable - it shows "flow" if the 
connection has been blocked in the last 5 seconds. This is driven by 
"last_blocked_age" and "last_blocked_by".

The rabbitmqctl command results you posted show some connections which 
had blocked some time in the past, all more than 5 seconds ago. 
Unfortunately I forgot to ask you to add "state" to the list of columns, 
to determine if they were blocked now. If we see any connections that 
were blocked by flow control a long time ago, and are still blocked, 
then I'm concerned.

Cheers, Simon

Simon MacMullen
RabbitMQ, VMware

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