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From Gordon Sim <g...@redhat.com>
Subject Re: flow control in Broker Federation on 0.22
Date Thu, 13 Nov 2014 18:12:18 GMT
On 11/12/2014 10:08 AM, Kyrie.Gao wrote:
> Hello Gordon,
> I did some experiments based on your suggestions, and the results sound that
> some of the option you mentioned doesn't have any effect. Uhmm...I am not
> sure if my test steps are right.
> /* To enable flow control over a federation link, you need to use the
> --ack option/
> The help page tells us its meaning “Acknowledge transfers over the bridge in
> batches of N”. When I set ack to a very huge value like 63537 and then set
> back to 10, no special things happen. May be it should be used on a queue
> route?

Yes, it appears that support for flow control with other routes did not 
get added until Qpid 0.24, so for 0.22 exchange links the --ack option 
would have no effect.

> ps: we use a static exchange route currently. a queue route cannot be used
> in our project because changing to it costs too much effort.
> /* flow control in the client is tied to the sender capacity. The back
> pressure by the broker is in the form of delayed acknowledgement of
> published messages and the number of outstanding unacknowledged
> published messages on a sender is giverned by the capacity  So for a low
> limit, you want to lower the capacity of the sender/
> I set a lower value for the capacity, say, from 50 to 1, and it has some
> effects on sending speed. It will need more time to send out all of the
> messages with the new value than the previous one, in another point of view,
> it can ease the broker’s pressure and reduce the possibility of the flood
> event issue. But by this way we cannot solve the problem thoroughly. In
> addition, by this way (change something by client side) we need to ask
> people from other team to do some fix.

Fair enough. Clients that send more messages than the queue can cope 
with will get an exception.

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