The client registers to the service by filling a registration form. On the registration form, the client chooses the event scenarios (e.g. subscription channels) of interest. In the AMQP broker the client-subscription queue connection is established, to receive messages from an AMQP message queue. Clients can connect through an API Gateway and authenticate using mTLS and API Gateway validates the clients certification. After authentication, service consumers can access the AMQP delivery channel and receive data by connecting with appropriate credentials, that are made available after registration.
Only preconfigured event scenario based channels are available, no explicit subscribe/unsubscribe API is provided. Whenever new data is available (e.g. a new digitalNOTAM), messages are generated and pushed to AMQP message queues. Clients can only access their selected scenario queues.
The service behaviour is in accordance with the Asynchronous Request-Reply pattern detailed in the Message Exchange Patterns: Identification Guidelines. The typical behaviour is as follows: BROKERED_PUBLISH_SUBSCRIBE_WITH_PUSH_MECHANISM - A Publish/Subscribe pattern with push mechanism introducing a layer of decoupling between the publisher and subscribers by means of a broker.