Efficient Recovery Algorithm in Real-Time and Fault-Tolerant Collaborative Editing Systems

This paper discusses the fault-tolerant issues in real-time collaborative editing systems. In order to make the realtime collaborative systems more reliable, an efficient recovery algorithm is presented. A crashed client site can be recovered by transmitting the system’s final state from the server. If the volume data associated with final state is huge, the recovery latency becomes significant large. We investigate a new approach, in which each client site maintains a local final state that is generated periodically. Thus, if a failure occurs in the client or links, the client can rejoin the collaborative editing systems by loading the local final state instead of obtaining the state from the remote server that may result in a noticeable delay. The key point in our approach is the consistency between the local state and remote state, which is maintained properly in our algorithm. Interval time between a client join and leave the system is an important metric that address in our paper. We derive the equations of this interval time to measure the performance of the recovery algorithm. Regarding to this interval time, the performance of the system can be enhanced by determining an optimal frequency of generating local final state.