In my testing of 5.2.0 I found that the solution in AMQ-1509 breaks queue
subscriptions with selectors on a Network of Brokers with some messages not
getting delivered. The scenario is two brokers A and B with a publisher
publishing to A and subscribers with different selectors on A and B. Some
of the messages that should be delivered to the subscriber on A are moved
over to B and are never delivered. It appears that the network connector
subscription on broker B is stealing the message before it can be delivered
to the local client subscriber on A. And since there is no subscriber on
broker B with the selector, the message gets parked. Backing out the change
in 1509 resolves the problem.
It would seem that the network connector subscription should retain the
selector for queues but not use the selector for topics to avoid duplicate
delivery. Thus, topic messages would need to be forwarded via a single
subscriber over the network channel, and queue messages would be forwarded
over a separate network connector subscription for each client subscription.
Since the ConduitBridge and DurableConduitBridge already have the
characteristic of working better for topics by not replicating messages and
the DemandForwardBridge is better suited for queues by accuratly load
balancing across the cluster. My proposed solution would be to remove the
topic selector fix provided in AMQ-1509 from the DemandForwardBridge and
leave it in the other two bridges. With this change in a place, two network
connectors would be used as a configuration to forward all messages in
network of brokers, one network connector for queues, and one network
connector for topics. Here is a sample configuration.
<!-- The store and forward broker networks ActiveMQ will listen to -->
<networkConnectors>
<!-- configure a bridge for queues that forwards each subscription on
demand -->
<networkConnector uri="static://(tcp://hostname-b:61616)"
name="queue-bridge"
dynamicOnly="true"
conduitSubscriptions="false"
decreaseNetworkConsumerPriority="false">
<excludedDestinations>
<topic physicalName="topic://>"/>
</excludedDestinations>
</networkConnector>
<!-- configure a bridge for topics using a conduit subscription -->
<networkConnector uri="static://(tcp://hostname-b:61616)"
name="topic-bridge"
conduitSubscriptions="true"
decreaseNetworkConsumerPriority="false">
<excludedDestinations>
<queue physicalName="queue://>"/>
</excludedDestinations>
</networkConnector>
<networkConnectors>
What do you think, is this the right way to go? I have a working solution
that I could submit as a patch if interested.
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