Notifications and blocking tasks are separate mechanisms that are implemented over the same AMQP message bus.

When a task is blocked, an extension is responsible for delivering a message to query the status of the related object or take action on the blocked task.

Resume, Progress (that was made), Abort, and Continue are valid calls against a blocking task.

Configure the timeout for a blocking task globally in vCloud Director.

You can abort a waiting blocking task directly from the VMware vCloud Director UI.