In this demonstration, we show how to implement a distributed game using Explicitly Consistent Replicated Objects (ECROs). This demonstration is intended for those that are interested in programming highly-available distributed systems under eventual consistency. We cover the design of a replicated data type and its integration within Squirrel, a distributed key-value store.

We start with a brief introduction to ECROs. Afterwards, we introduce a sequential voting game that resembles interactive tv-shows where candidates battle against each other and viewers can vote on candidates. After some time, the candidate with the least number of votes is eliminated. The game continues until a single candidate remains. We show how to turn the sequential voting game into a fully distributed game. To this end, we extend the sequential implementation with a distributed specification of the game’s shared state. We combine both the implementation and the specification of the game into an ECRO (i.e. a replicated data type). Then, we show how to store game replicas in Squirrel and how to react to state changes. The result is a fully distributed voting game that is replicated across all viewers such that the game is (offline) available and provides low latency while ensuring that all viewers eventually converge to a consistent state. We show how to deploy the application using Docker and experiment with several scenarios including concurrent updates and network failures.