- A Message represents data in transit through a system.
- A Message consists of a payload and optional attributes that describe the payload.
- Data is transmitted to one or more subscriptions.
- A Topic is a feed of data.
- Subscribing Forwarder ensures data delivery.
- Subscriptions expresses an interest in receiving messages.
- Subscriptions register each delivery of data.
- Subscription determines which subscribers are registered to receive a message and queues up the messages to be sent.
- Subscribers can receive data through pull or push.
- Subscribers receive messages by Pub/Sub, pushing them to the endpoint or by pulling them from the service.
- Subscribers can be configured to receive messages on a push or pull basis.
- Publishing Forwarder receives data from the publisher on behalf of the topic.
- Pull subscribers use HTTPS requests to google APIs.
- Push subscribers can accept post requests over HTTPS.
- Push subscribers use webhook endpoints.
- Pub is short for publishers.
- Sub is short for subscribers.