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From "Thomas R. Corbin" <>
Subject Not quite sure where to go next - network bridging, reliable delivery, store and forward.
Date Wed, 01 Oct 2008 16:25:17 GMT

Now, it seems like the recommendation is for Master/Slave for reliable 
delivery, but I don't think we can do that.

We've got field laptops which may or may not have connectivity with the central 
office, but they want to be able to run the application and have it send 
messages that get delivered when the network comes up.

And the client wants the central office to be able to send assignments to the 
field whether or not the network to the field laptop is up.

So for the field laptops I've set up an embedded broker which then connects to 
a central office broker.   The reason is that the application won't come up if 
there isn't a local broker that it can connect to.  If the application is 
started w/o a local broker or a connection to the central office it doesn't come 
up.   Plus, I wanted the local message persistence so that the user of the 
application can trigger messages to be sent even when the connection to the 
central office isn't present.

In the central office we've get server processes also with embedded brokers.

I've been fiddling with the setup configuration for the embedded brokers and the 
central office brokers and I've gotten to the point that messages from the field 
get sent to the central office on reconnect, but don't get sent from the central 
office to the field on reconnect.

And everything works if everything is connected.   But if the laptop isn't 
connected to the central office when the central office sends out assignments to 
the field, then the laptop will never see those messages.

I've tried using durable subscription topics, I've tried setting 
"conduitSubscriptions" to both true and false - and I'm not sure if I should 
set it one way for the central office broker and the same or different for the 
laptop and server process embedded brokers.

The network kind of looks like this:

Field laptop|---------|central office broker|-----|Server Process|

The central office broker is intended to be the "master", in as much as there is 
a master - this isn't really a master/slave setup.

I can use JMX to look at the enqueue/dequeue counts to see where messages are 
getting hung up - but I am not ever sure why.

I had thought that with durable subscriptions, the messages would get sent, 
but that *seems* not to be the case.

I have looked through ActiveMQ bug reports and the online documentation.  Of 
which there is a lot, but I am still quite confused.

Seeing as how I'm doing the embedded broker set up in Groovy, rather than in 
spring or xbean - should I explicitly be using a DemandForwardingBridge as in 
the ThreeBroker tests?   Or does the underlying code just use it anyway?

What would that imply for the activemq.xml config file for the master broker?   
Is there configuration that explicitly says use a DemandForwardingBridge?  Or 
is the DemandForwardingBridge not the issue?

What should these values be set to?


Sorry for such a newbie set of questions and so long an email.

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