In large distributed topologies, it is sometimes difficult to build routing logic that will be flexible and adaptable to changing topologies. For example, introducing a new messaging node into the environment should not require recoding existing applications.
Recommendation Sonic offers a powerful feature known as Global Subscription Architecture (GSA). This allows a producing application to simply publish content to the bus and have it dynamically distributed to any site where there are subscribers. This feature can greatly simplify maintenance and provides the ability to have data truly routed globally across the bus.
Benefits of GSA when routing across sites are:
No manual configuration of routes at the sending node.
Use of wildcards reduces administrative overhead. Rules are configured once and propagated across the cluster.
Selective subscription propagation optimizes messaging across network links. If a particular subscription does not exist for a remote node, the sending node will not send any messages. For applications with frequently changing or intermittent subscriptions, this can be a big savings.
Message selection at the remote node provides the ability to further optimize messaging traffic between two nodes.
In a large messaging environment managing routes for large numbers of subscriptions could be error prone. GSA eliminates many human errors that could be caused through manual configuration.
On the sending cluster, subscriptions are automatically propagated across the entire cluster; no administration is required.
Use of topic forwarding provides the capability to move data across multiple nodes for more complex topologies.
One consideration to make when adopting this architecture is the use of topics versus queues. It is certainly possible to keep the data in the topic domain globally, but there are certain deployment advantages with queues. For this reason, one architecture to consider is to have lightweight routers in each location that:
Subscribe to the topic in the remote location.
Route to a queue in the local location.
Using this architecture, one can recognize the advantage of GSA's global distribution as well as the deployment advantages of queues.
The following diagram shows an architecture using GSA:
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You can get more info at documentation.progress.com/.../mq_deploy.pdf in the 'Global Subscriptions' section.