Fault Tolerant, Scalable Middleware Services Based on Spring Boot, REST, H₂ and Infinispan

Control systems require several, core services for work coordination and everyday operation. One such example is Directory Service, which is a central registry of all access points and their physical location in the network. Another example is Authentication Service, which verifies callers identity and issues a signed token, which represents the caller in the distributed communication. Both cases are real life examples of middleware services, which have to be always available and scalable. The paper discusses design decisions and technical background behind these two central services used at CERN. Both services were designed using latest technology standards, namely Spring Boot and REST. Moreover, they had to comply with demanding requirements for fault tolerance and scalability. Therefore, additional extensions were necessary, as distributed in-memory cache (using Apache Infinispan), or Oracle database local mirroring using H₂ database. Additionally, the paper will explain the tradeoffs of different approaches providing high-availability features and lessons learnt from operational usage.