DATA FLOW IN PUB/SUB

PUB/SUB MESSAGE FLOW

The diagram given below is a look of the components in the Pub/Sub system and how messages flow between them:


1. A publisher application creates a topic in the Pub/Sub service and then sends some messages to the topic. The message consists of a payload and optional attributes that describe the related payload content.

2. The service must ensure that published messages are retained on behalf of respective subscriptions. A published message is retained for a subscription until it is formally acknowledged by any subscriber which is consuming messages from that subscription.

3. Pub/Sub then forwards messages from a topic to all its respective subscriptions individually.

4.  A subscriber receives messages either by Pub/Sub pushing them to that subscriber's chosen endpoint, or by the subscriber pulling them from the service.

5. The subscriber then sends an acknowledgement to the Pub/Sub service for each of received message.

6.    The service finally removes the acknowledged messages from the subscription's message queue.

 

DATA FLOW

Data flow in pub/sub service is principally dependent on the publisher application, topic, and a subscribing application. A publisher application can be any application that makes an HTTPS (Hypertext Transfer Protocol Secure) requests to the online services, app engine, publishes the messages to the subject. A subscribing application at the subscribing end subscribes to that topic. A subscriber may be a pull subscriber, or a push subscribe. A pull subscriber requests a Hypertext Transfer Protocol Secure request to the Google APIs and a push subscriber accepts the information that is streaming over HTTPS. The communication is often in any manner like many subscribers to at least one publisher and one publisher to several subscribers.

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