OSB 10gR3 (WLS 10.3) - Distributed Queues & Load Balancing

Question

I have a question in relation to distributed queues and its JMS proxy service consumer in OSB
I've set up a uniform distributed queue deployed using a sub-deployment resulting in the queue being targeted to the respective JMS servers in the cluster.
I've then set up a messaging service using JMS as the transport with the following URI
jms://server1:7011,server2:7012/weblogic.jms.XAConnectionFactory/myQueue
When I look at the monitoring tab of my distributed queue, I can see 16 current consumers to one of the members but none for the other one. My understanding is that the proxy is just a mere MDB and as such I thought WLS was optimised to make sure all MDB instances would listen to all members of the distributed queue. Why do I have 16 consumers to one member only?
Since only one member has consumers, any producer will always push messages to this member only. (I believe it is optimised to get a member with consumer(s) if any available)
I've also tried to use a custom Connection Factory deployed the same way my distributed queue was, and ensure the connection factory had load balancing enabled. But no success with this either.
jms://server1:7011,server2:7012/jms.MyConnectionFactory/myQueue
I looked at the deployment - though not directly performed by me but rather the bus console - and it looks like the application is targeted to the cluster.
How can I achieve true load balancing here, ensuring both members are consumed by my JMS proxy service?
In that case, would any produced message go to either member then as both have consumers?
Also, is the load balancing decision made by the producer when the Queue connection is created?
If so, how do you achieve true load balancing? Do you need to ask for a new Q connection each time you want to send a message rather than caching the connection?
Hope I am clear enough
Thanks
Arnaud

Answer 1

This confused me too!
The way I understand it, is that, as you say, a proxy service is like a single MDB. The MDB will bind to the queue it first finds when it connects.
The URL that you specify which contains your two servers but the first address in the URL is the one that will be used for the connection. If the first server is unavailable, then the second one will be used.
If you have a distributed queue, this doesn’t help much, as you do end up with one of the queue members with no consumers on it.
You can configure a forward delay for the distributed queue, which will cause WLS to forward messages to a queue with consumers, but this isn’t a good idea if you have large JMS messages as WLS needs to serialize and de-serialize across the network to move the message.
I think that what you have to do, is define two proxy services, one connecting to the first server, and the other connecting to the second.
I haven’t found a better way so far, but it does seem a bit over the top, but then, if you wrote a an external java client which attached to a distributed queue you would specify the connection url and it would behave in the same way – if you wanted it to bind to both distributed destination members, you would have to code it or run two instances, so maybe its just working as it should – even though it seems strange.
I think the producer will simply load balance across the distributed queue members, it doesn’t pay any attention whether there are to consumers attached – this happened to me the other day!!
Pete