Coordinating redundant OPC UA servers

Coordination is an important aspect of large scale distributed systems. The Open Platform Communications Unified Architecture (OPC UA) standard series presents an important challenge for coordination in its specifications for server redundancy. This paper discerns the coordination needs of OPC UA server redundancy and presents a solution based on the integration of OPC UA and ZooKeeper. A detailed description of the architecture, data model, and components of the resulting system is given. This is accompanied by a discussion of an implementation based on the open source ZooKeeper and open62541 libraries. The resulting system is shown to be capable of meeting the coordination needs of OPC UA redundancy.