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From Joel Schaubert <>
Subject Re: How to have a highly available and scalable setup using network of brokers?
Date Thu, 21 Jun 2007 15:10:12 GMT

Nicky Sandhu wrote:
> Joel Schaubert wrote:
>> What are the extra benefits of going to the more complicated setup of
>> pairs of master/slave's behind the load balancer instead of a flat space
>> of a network of brokers?
>  If a master were to fail then the slave would connect as a master to the
> network to deliver any messages that were in the master's queue/topic for
> consumers on other masters in the network. At least my idea was to not
> have any messages stuck in the failed master's queue and have them
> delivered by the slave. However the slave behind the load balancer would
> not get any load (fresh client connections) which would mean that the load
> after failure would be shared by remaining masters in the network.

What I have found during my testing of the network of brokers is that you do
get this behaviour.  If I write 100 message to broker A, then I kill it,
then I subscribe to broker B, I can read all of the messages. (and various
versions of this scenario tested in our QA environment).  What's also nice
about this is unlike master/slave, when broker A comes back up it will be
noticed by the load balancer and can take any new client connections then. 
Read the section on how to do recovery on a failed master in master slave,
it doesn't sound anywhere near as easy as a network of brokers behind a load

One thing to note if you try network of brokers is that the auto discovery
is very complete.  So if you had 2 different networks of brokers I don't
think auto discovery is useful because they would all join up into one big
network.  For example if you had one network in production, one for QA, I
think the autodiscovery would have every broker find every other broker.  We
are testing the method where you statically list each of the other brokers
you want to participate with.

Joel Schaubert

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