As you work with Extensibility and subscriptions within Cloud Assembly, you might encounter some terminology that is specific to the subscriptions and event broker service.

Table 1. Extensibility Terminology



Event Topic

Describes a set of events that have same logical intent and the same structure. Every event is an instance of an event topic.

You can assign blocking parameters to certain event topics. For more information, see Blocking event topics.


Indicates a change in the state in the producer or any of the entities managed by it. The event is the entity that records information about the event occurrence.

Event Broker Service

The service that dispatches messages published by a producer to the subscribed consumers.


The event data that contains all the relevant properties related to that Event Topic.


Indicates that a subscriber is interested in being notified about an event by subscribing to an event topic and defining the criteria that triggers the notification. Subscriptions link either extensibility actions or workflows to triggering events used to automate parts of the applications life cycle.


The users notified by the events published to the event broker service based on the subscription definition. The subscriber can also be called a consumer.

System Administrator

A user with privileges to create, read, update, and delete tenant workflow subscriptions and system workflow subscriptions using Cloud Assembly.

Workflow Subscription

Specifies the event topic and conditions that trigger a vRealize Orchestrator workflow.

Action Subscription

Specifies the event topic and conditions that trigger an extensibility action to run.


A vRealize Orchestrator workflow that is integrated within Cloud Assembly. You can link these workflows to events within subscriptions.

Extensibility Action

A streamlined script of code that can run after a triggering event within a subscription. Extensibility actions are similar to workflows, but are more lightweight. Extensibility actions can customized from within Cloud Assembly.

Action Runs

Accessible through the Action Runs tab. An action run is a detailed log of extensibility actions that have run in response to triggering events.