Request/Reply Interactions
Demand for data drives request/reply interactions. A client requests data from a server; the server computes an individual response and returns it to the client. Communication flows in both directions, as in Demand-Driven Request/Reply Interaction. The complete interaction consist of two point-to-point messages—a request and a reply.
Figure 10: Demand-Driven Request/Reply Interaction
Demand driven computing is well-suited for distributed applications such as these examples:
• | Transaction processing (as in ATM banking). |
• | Database query (with a remote DBMS). |
• | Factory equipment control. |
In request/reply interactions, data producers coordinate closely with data consumers. A producer does not send data until a consumer makes a request. Each program sends its message to a specific inbox name within the other program.
The server sends replies specifically to the client that requested the data. The requesting client listens until it receives the reply, and then stops listening (unless it expects further installments of information).
Rendezvous software supports request/reply interactions with point‑to‑point communication.