Universal Messaging 10.15 | Concepts | AMQP | AMQP Guide | Message Transport
 
Message Transport
AMQP message transfers (also called deliveries) can occur in either direction, with AMQP links created in pairs from the parent AMQP session.
Note:
In Universal Messaging, delivery tags are mapped to a <long>:<long> naming scheme implying <um store unique id>:<UM event EID>.
AMQP defines the following approaches with regard to message transfers (AMQP deliveries):
*At Most Once
*At Least Once
At Most Once
AMQP deliveries occurring via settled message transfers can be used for a "fire and forget" publishing / subscribing model, as they do not require an explicit acknowledgment.
Publishing
AMQP publishing occurs when an AMQP application container (Sender) attaches a link to an AMQP node (Receiver) and initiates message deliveries. In the at-most-once model, message deliveries are sent pre-settled by the sender with no expectations of acknowledgment from the receiver.
Note:
In Universal Messaging, pre-settled message transfers are mapped to UM reliable publishing.
Subscribing
AMQP subscribing occurs when an AMQP application container (Receiver) attaches a link to an AMQP node (Sender) causing a flow of deliveries from the sender node to the application node. In the at-most-once model, message deliveries are sent pre-settled by the sender with no expectations of acknowledgment from the receiver.
Note:
In Universal Messaging, pre-settled message transfers are mapped to UM reliable subscriptions (no Durability / ACKs).
At Least Once
AMQP deliveries occurring via unsettled message transfers require an explicit settlement via acknowledgments, whether initiated by an application container or a broker container.
Publishing
AMQP publishing occurs when an AMQP application container (Sender) attaches a link to an AMQP node (Receiver) and initiates message deliveries. In the at-least-once model, message deliveries are sent unsettled by the sender with an expectation of acknowledgment from the receiver.
Note:
In Universal Messaging, un-settled message transfers are mapped to UM single event TX publishing.
Subscribing
AMQP subscribing occurs when an AMQP application container (Receiver) attaches a link to an AMQP node (Sender) causing a flow of deliveries from the sender node to the application node. In the at-least-once model, message deliveries are sent un-settled by the sender with an expectation of acknowledgment from the receiver. The AMQP source durability configuration indicates whether the durable subscription state should be in-memory or persistent (CONFIGURATION or UNSETTLED_STATE respectively).
Note:
In Universal Messaging, unsettled message transfers are mapped to synchronous, individual ACK subscriptions.