Each services interface of the CCS business services relies on the concept of AMQP queues and topics.
The CCS customer shall use an implementation of the AMQP 1.0 specification to connect to the CCS provider AMQP 1.0 endpoint.
The CCS provider endpoint is an AMQP 1.0 broker managing queue and topics.
The message payloads are encoded following a protobuf format.
The message exchange patterns used by the CCS services are request/reply and publish/subscribe. The CCS customer acts as requester and subscriber. The CCS provider acts as responder and publisher.
Concerning publish-subscribe, the CCS customer subscribes to a CCS distribution service by directly listening to an appropriate AMQP topic, which name follows the CCS derivation rules.
The subscription to CCS Distribution Services is not performed via subscription operations, but by connecting to the appropriate AMQP Topic described in the .protobuf files as topic://..
The subscribers can filter the messages they want to receive by using the filter parameters defined for each subscription operation.
Please note that, after subscribing to a CCS Distribution Service, the current repository of messages needs to be obtained from CCS via the get operation defined for each CCS Distribution Service (see "Subscription" section of the distribution operation of the service).
- If the CCS platform restarts while the Customer is connected to the AMQP Broker, the current repository of messages is published again.
- The acknowledgement that a Customer receives to his request ("RequestReport") may be received after the data distribution that this request has triggered, as these two messages are managed asynchronously by AMQP Queues and Topics
Concerning request-reply the CCS customer sends a request by sending a message to an appropriate AMQP queue, which name follows the CCS derivation rules, to make a request. The request message contains the name of the queue into the CCS customer listens and in which the reply from the CCS provider is expected.