7. Orchestration and Extension : 7.3 vCloud Messages : 7.3.1 Message Publication
   
7.3.1 Message Publication
The system administrator can configure vCloud Director to enable the publication of messages for all event notifications or for specific blocking tasks:
*Notifications are published on user-initiated events (for example, creation, deployment, and deletion of a vApp) and system-initiated events (for example, vApp lease expiration) that contain the new state of the corresponding vCloud Director entity.
*Blocking tasks suspend long running operations started as a task before publishing messages and wait until a system administrator approves or rejects the request.
Message publication is enabled for operations started in the vCloud Director UI or vCloud API.
vCloud Director publishes notification messages to an Advanced Message Queuing Protocol (AMQP) exchange (requires AMQP version 0.9.1 supported by vFabric RabbitMQ version 2.0 and later).