Publish/Subscribe

 

The pub/sub based TradeStreamerMDB subscribes to a message topic called TradeStreamerTopic. Quote data for individual stocks is published to this topic as prices change, providing a real-time streaming quote feature in Trade3. The prices change every time some stock is bought or sold.

Some important points to note on the influence the functionality has on the topology are:

1. If the Trade3 application is clustered, then each appserver needs to get the publications on price changes. If this does not occur then the prices will not be kept in synchronization across the cluster. This means having only one message broker doing the work (or one cluster of message brokers).

2. By default, the MDB is using non-durable subscriptions. This avoids any restrictions imposed from using durable subscriptions. See Client ID and Enable Clone support on a TCF for more information.

Now that we understand how Trade3 needs to use JMS we will move on to apply some of the guidelines described in this chapter and create some topologies.

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