Welcome back! In this lesson, we will explore how to implement the fan-out messaging pattern using Google Cloud messaging services. The fan-out pattern allows a single publisher to send messages to multiple independent subscribers, enabling efficient and scalable communication between different parts of your application. By leveraging topics and multiple subscriptions, you can ensure that each subscriber receives a copy of every message published.

Consider a scenario with three services: Service A, Service B, and Service C. Service A needs to send updates to both Service B and Service C. Instead of sending messages directly to each service, we can create a topic that acts as a central channel. Both Service B and Service C can then subscribe to this topic, ensuring that they each receive all messages published by Service A.

Let's see how Service A can publish messages to a topic. We'll also include additional message attributes to provide more context to subscribers.

Output:

In these examples, a message is published to the service-a-updates topic. The second message includes attributes such as priority and department, which can be used by subscribers to filter or process messages accordingly.

To ensure that both Service B and Service C receive all messages from Service A, we create separate subscriptions to the same topic. Each subscription acts as an independent channel, allowing each service to process messages at its own pace.

In this lesson, we explored how to implement the fan-out messaging pattern using Google Cloud messaging services. By creating a topic and multiple subscriptions, a single publisher can efficiently distribute messages to multiple subscribers. This pattern enables scalable and reliable communication between different components of your application, allowing each subscriber to process messages independently. Experiment with creating additional topics and subscriptions to further customize your messaging architecture.