An SOA-Based Design of JUNO DAQ Online Software

The Online Software, manager of the Jiangmen Underground Neutrino Observatory (JUNO) data acquisition (DAQ) system, is composed of many distributed components working coordinately. It takes the responsibility of configuring, processes management, controlling, and information sharing. The design of service-oriented architecture (SOA) makes the Online Software lightweight, loosely coupled, reusable, modular, self-contained, and easy to be extended. All the services in the SOA distributed Online Software system will send messages to each other without an intermediate broker. Hence, the services can operate independently. ZeroMQ is chosen but not the only technical choice as the low-level communication middleware because of its high performance and convenient communication model while using Google Protobuf as a marshaling library to unify the pattern of message contents. The partitioning of the JUNO detector into smaller subdetectors and segments ensures that these subsystems can either be readout together or independently. All running data except the raw physics events will be transmitted, processed, and recorded to the database. High availability (HA) mechanisms are foreseen to reduce single points of failure (SPOF) in the distribution system. This paper will introduce all the core services' functionality and techniques in detail.