Core

The core software unit of the middleware provides the key algorithms needed for the communication between applications.

Middleware Message

Middleware is a service-oriented message passing system. The Message class is its fundamental unit of communication. This class consists of a header and a payload. The header has the following information:

  • Service ID - identifies the service to which the message belongs.

  • Member ID - identifies the specific member function of the service that is being invoked.

  • Request ID - identifies the specific request being made.

  • Instance ID - identifies the instance of the service (multiple instances may exist).

  • Source cluster ID - identifies the cluster from which the message originated.

  • Destination Cluster ID - identifies the cluster to which the message is being sent.

  • Address ID - identifies the recipient of the message within the destination cluster.

The middleware services’ nodes will be scattered across different clusters in the ECU. This means that messages can travel between clusters. Each Message must carry information about its origin and destination. Additionally, a message may have several possible recipients. Each recipient needs a unique identifier after system initialization. To this end, the header contains the source cluster ID, target cluster ID, and address ID fields.

Finally, the payload contains the actual data being transmitted. The message capacity is defined by Message::MAX_PAYLOAD_SIZE as Message::MAX_MESSAGE_SIZE - sizeof(Message::Header) - sizeof(uint32_t). With the current 64-byte message layout, this capacity is 48 bytes. Payloads that fit and are trivially copyable are stored in the message’s internal buffer. Larger or non-trivial payloads are copy-constructed into middleware-managed external storage, and the message records an external payload offset and the hasExternalPayload flag. Message also supports an ErrorState payload for error responses.