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From yg_cvg <>
Subject Re: question about the store/forward algorithm
Date Tue, 11 Dec 2007 00:36:34 GMT

Thank you for your response.  So, the messages spread out to clients in
roughly a BFS pattern.

rajdavies wrote:
> 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  
> manner.
> However - by default the number of hops messages/subscriptions are  
> allowed to pass through is 1 - see 
> networks-of-brokers.html
> 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
> cheers,
> 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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>> the-store-forward-algorithm-tf4965292s2354.html#a14223478
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