How to implement pub-sub fan-out model in app integrations.

[govardhandatla]

Hello,

I have created a pubsub topic and two subscriptions under the same topic.  I am doing a poc to test fanout. 
Looks like pub/sub trigger only accepts topic name as input and it automatically creates a subscription in topic. Can you please guide me on how to test this out.

[salonijuneja]

Hi @govardhandatla 
You can configure multiple integrations with pubsub trigger subscribing to the same topic. On publish, it will automatically create the subscription. The subscription is in the same project as integration and can be edited if needed.
When you publish a message to the topic, all the integrations with pubsub trigger configured for that topic will be executed.

[govardhandatla]

Hi @salonijuneja ,
So, when I try to publish an integration with same pub/sub trigger. I am receiving this error:
Failed to publish integration version. Error: Duplicate Trigger Id [cloud_pubsub_external_trigger/projects/*******/subscriptions/******_go-app-int-poc] found. Please change trigger Id to make it unique.

[shaaland]

You can also just use 1 PubSub trigger, and then use the Integration that receives the messages to fan it out to multiple endpoints...like your diagram is showing, except the fan out would happen inside the integration flow instead of at PubSub.  Essentially, the integration flow becomes the router to multiple destinations.

Meanwhile, we can also investigate to see if we can add the trigger id to the configuration so that you could make each pubsub trigger unique, so that pubsub could have many subscriptions to many integration flows.