Overview of using Universal Messaging in Apama applications
In an Apama application, correlators and adapters can connect to Universal Messaging realms or clusters. A correlator or adapter connected to a Universal Messaging realm or cluster uses Universal Messaging as a message bus for sending Apama events between Apama components. Connecting a correlator or adapter to Universal Messaging is an alternative to
Specifying a connection between two correlators by executing the
engine_connect correlator tool. This is the main reason to use
Universal Messaging.
Defining connections between an adapter and particular correlators in the
<apama> element of an adapter configuration file. This is a secondary reason to use
Universal Messaging. You might find that having some adapters connected to
Universal Messaging is a good fit for your application.
Using Universal Messaging can simplify an Apama application configuration. Instead of specifying many point-to-point connections, you specify only the address (or addresses) of the Universal Messaging realm or cluster. Apama components connected to the same Universal Messaging realm can use Universal Messaging channels to send and receive events. (Universal Messaging channels are equivalent to JMS topics.) Connections to Universal Messaging are automatically made as needed, giving extra flexibility in how the application is designed.
When an Apama application uses Universal Messaging, a correlator automatically connects to the required Universal Messaging channels. There is no need to explicitly connect Universal Messaging channels to individual correlators. A correlator automatically receives events on Universal Messaging channels that monitors subscribe to and automatically sends events to Universal Messaging channels.
When using the connectivity plug-in for Universal Messaging, you can also talk to non-Apama applications which are connected to Universal Messaging and configure a chain definition to translate those message payloads into ones suitable for Apama.
