FRIB, East Lansing, Michigan, USA
RecCaster is an EPICS module which is responsible for uploading Process Variables (PVs) metadata from the IOC database to a central server called RecCeiver. The RecCeiver service is a custom-built application that passes this data on to the ChannelFinder, a REST-based search service. Together, RecCaster and RecCeiver form the building blocks of RecSync. RecCeiver is not a distributed service which makes it challenging to ensure high availability and fault-tolerance to its clients. We have implemented a new version of RecCaster which uploads the PV metadata to ETCD. ETCD is a commercial off-the-shelf distributed key-value store intended for high availability data storage and retrieval. It provides fault-tolerance as the service can be replicated on multiple servers to keep data consistently replicated. ETCD is a drop-in replacement for the existing RecCeiver to provide data storage and retrieval for PV metadata. Also, ETCD has a well-documented interface for client operations including the ability to live-watch the PV metadata for its clients. This paper discusses the design and implementation of RecSyncETCD as a fault-tolerant service for storing and retrieving EPICS PV metadata.
