Transaction Models for Massively Multiplayer Online Games

Massively Multiplayer Online Games are considered large distributed systems where the game state is partially replicated across the server and thousands of clients. Given the scale, game engines typically offer only relaxed consistency without well-defined guarantees. In this paper, we leverage the concept of transactions to define consistency models that are suitable for gaming environments. We define game specific levels of consistency that differ in the degree of isolation and atomicity they provide, and demonstrate the costs associated with their execution. Each action type within a game can then be assigned the appropriate consistency level, choosing the right trade-off between consistency and performance. The issue of durability and fault-tolerance of game actions is also discussed.