8.4. Distributed Communications - Middleware

In a distributed control system the use of middleware enables communication between different components deployed in different processes or computers. This makes middleware software pervasive. A middleware agnostic architecture allows the decoupling of applications from the specific implementation. The SWCS communication requirement is given by SWC-6879, Communication Protocols: SWCS shall define a set of software protocols and APIs that allow the communication with the required performance between different components.

ZeroMQ is used for communications between distributed components, chosen for its desirable features. Given that the project is in early stages and that the infrastructure software is likely to continue evolving, this selection can be revised in the future as fitting. Front–end software deployed in a browser uses WebSockets to communicate with the rest of the distributed components. The serialization/deserialization of transmitted data packages is accomplished using MessagePack.

GMT is developing several prototypes to validate the use of these technologies. These prototypes include the use of NoSQL databases like Mongodb, scripting languages like Coffeescript, user interface libraries based on HTML5 and SVG like d3.js, event-driven environments like node.js or high performance middleware libraries like zeromq, MessagePack or ProtocolBuffers.