Protocol modularity in systems for managing replicated data

The authors describe their experience in attempting to modularize Consul, a fault-tolerant system for managing replicated data. Their experience is that, while modularity is needed to simplify the design and implementation of such systems, protocol dependencies, both direct and indirect, impact the way in which protocols are designed and implemented. They also identify certain operating system features that simplify such a design. Based on this experience, work is in progress to develop a new model for fault-tolerant protocols that will facilitate modularization