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From Rob Davies <>
Subject Re: question about the store/forward algorithm
Date Sat, 08 Dec 2007 07:47:15 GMT
Hub and spoke architecture - as you've described - is certainly a  
valid one.
By default, messages are forwarded to brokers that express an  
interest in the message by themselves having a consumer interested in  
the remote message. Subscription information is propagated from one  
broker to the next, and if configured to do so - that subscription  
information will be propagated further around the network - in BFS  

However - by default the number of hops messages/subscriptions are  
allowed to pass through is 1 - see 
So providing you configure the networkTTL to be equivalent to the  
maximum number of hops - your messages should be able to propagate  
across multiple broker-to-broker steps. Messages/subscriptions carry  
around information about who they've visited - so we can prevent  
cycles happening.

Hope that helps


Rob -Enterprise Open Integration

On Dec 8, 2007, at 12:19 AM, yg_cvg wrote:

> This may seem to be more of a developer question, but I think it  
> applies
> here.  We are considering using ActiveMQ in a large distributed  
> network.
> The network is spread all over the world and consists of many small
> "regions," each of which contains a few servers.  At any time, a  
> piece of
> data can come in to one of these servers and should then be sent as  
> quickly
> as possible to not only every server in the region, but to every  
> server in
> ALL regions.  So, basically, there is one big JMS Topic to which  
> everyone is
> subscribed.
> I figure we'd organize each region into some kind of a hub/spoke  
> thing, or
> whatever, to ensure that the message gets sent to everyone in the  
> region.
> Then, we'd hook up the "leader" (hub) ActiveMQ servers from each  
> region
> together.  The question is how to organize this network of leaders  
> in the
> best way possible.  I mean, it depends on the physical distance  
> between any
> given pair of regions, etc.
> My question isn't this, though, but something that might help  
> figure out a
> good way to do this.  It seems I need to understand the ActiveMQ  
> forwarding
> algorithm if I want to figure out how to arrange the broker network  
> for
> maximum effect.  What is the exact algorithm used for broker  
> forwarding of a
> given pub/sub message?  I have read
> but don't get exactly how it works, at least for pub/sub, as  
> opposed to a
> queue.  For a given forwarding broker, does the Message get sent to  
> each
> connected broker except the one from which it came, unless the  
> Message has
> already been to this forwarding broker (i.e., there is a cycle)?   
> Or is the
> Message somehow kept on only one broker at a given time? Does it to  
> BFS or
> something cool like that?  Any details are welcome.
> Any other advice on the general problem at hand is also welcome.  I  
> am new
> to JMS and ActiveMQ.
> -- 
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