Apama 10.15.0 | Connecting Apama Applications to External Components | Standard Connectivity Plug-ins | The Universal Messaging Transport Connectivity Plug-in | Overview of using Universal Messaging in Apama applications | Comparison of Apama channels and Universal Messaging channels
 
Comparison of Apama channels and Universal Messaging channels
In an Apama application configured to use Universal Messaging, when an event is sent and a channel name is specified, the default behavior is that Apama determines whether there is a Universal Messaging channel with that name. If there is, then Apama uses the Universal Messaging message bus and the specified Universal Messaging channel to deliver the event to any subscribers. Subscribed contexts can be in either the originating correlator or other correlators connected to the Universal Messaging broker.
If a Universal Messaging channel with the specified name does not exist, then the default is that the channel is an Apama channel. An event sent on an Apama channel is delivered to any contexts that are subscribed to that channel.
Regardless of whether the channel is a Universal Messaging channel or an Apama channel, events are delivered directly to receivers that are connected directly to the correlator.
The following table compares the behavior of Apama channels and Universal Messaging channels.
Apama channels
Universal Messaging channels
Configuration of multiple point-to-point connections.
Each execution of engine_connect specifies the correlator to connect to. Each IAF adapter configuration specifies each correlator that adapter connects to.
Correlators and IAF adapters require explicitly set connections to communicate with each other.
Specification of the same Universal Messaging realm address or addresses.
Startup options for connected correlators specify the same Universal Messaging realm to connect to. Each IAF adapter configuration specifies the same address for connecting to Universal Messaging.
Correlators and IAF adapters automatically connect to Universal Messaging to communicate with each other.
Configuration changes are required when an Apama component is moved to a different host.
No configuration change is needed when an Apama component is moved to a different host if both hosts are connected to the same Universal Messaging realm.
Outside a correlator, channel subscriptions can be from only explicitly connected Apama components.
Outside a correlator, channel subscriptions can be from any Apama component connected to the same Universal Messaging realm.
Events sent on an Apama channel go directly to subscribers.
Events sent on a Universal Messaging channel go to the Universal Messaging broker and then to subscribers.
Connection configurations must be synchronized with application code.
Connection to a Universal Messaging realm is independent of application code.
Less efficient for sending the same event to many Apama components.
More efficient for sending the same event to many Apama components.
More efficient when sending an event to a context in the same correlator. The event stays inside the correlator.
Less efficient when sending an event to a context in the same correlator. The event leaves the correlator, enters the Universal Messaging realm, and then returns to the correlator.
Default channel, the empty string, is allowed.
No default channel.