Fermilab, Batavia, Illinois, USA
Current trends in the architectures of software systems focus our attention on building systems using a set of loosely coupled components, each providing a specific functionality known as service. It is not much different in control and monitoring systems, where a functionally distinct sub-system can be identified and independently designed, implemented, deployed and maintained. One functionality that renders itself perfectly to becoming a service is archiving the history of the system state. The design of such a service and our experience of using it are the topic of this article. The service is built with responsibility segregation in mind, therefore, it provides for reducing data processing on the data viewer side and separation of data access and modification operations. The service architecture and the details concerning its data store design are discussed. An implementation of a service client capable of archiving EPICS process variables and LabVIEW shared variables is presented. The use of a gateway service for saving data from GE iFIX is also outlined. Data access tools, including a browser-based data viewer (HTML 5) and a mobile viewer (Android app), are also presented.
