Apama 10.3 | Apama Documentation | Connecting Apama Applications to External Components | Standard Connectivity Plug-ins | The Universal Messaging Transport Connectivity Plug-in | EPL and Universal Messaging channels
EPL and Universal Messaging channels
In an Apama application that is configured to use Universal Messaging, you write EPL code to subscribe to channels and to send events to channels as you usually do. The only difference is that you cannot specify the default channel (the empty string) when you want to use a Universal Messaging channel. You must specify a Universal Messaging channel name to use Universal Messaging.
As with all connectivity plug-ins, the EPL application is responsible for telling the system when it is ready to start receiving events with onApplicationInitialized. See also Sending and receiving events with connectivity plug-ins.
A monitor that subscribes to a Universal Messaging channel causes its containing context to receive events delivered to that channel. There is nothing special you need to add to your EPL code.
Using Universal Messaging channels makes it easier to scale an application across multiple correlators because Universal Messaging channels can automatically connect parts of the application as required. If you use the EPL integer.incrementCounter("UM") method, remember that the return value is unique for only a single correlator. If a globally unique number is required, you can concatenate the result of integer.incrementCounter("UM") with the correlator's physical ID. Obtain the physical ID from Apama's Management interface with a call to the getComponentPhysicalId() method. For further information, see Using the Management interface.

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