Data Replication in Offline Web Applications: Optimizing Persistence, Synchronization and Conflict Resolution

As HTML5 features like web-storage and offline web-apps become more widely supported by modern browsers, an increasing number of web applications push their logic to the client. The consequence of this decentralization trend is that part of the application data now lives on the client-side. In order to keep this mobile data consistent and meaningful over time, it has to be replicated between all clients in the network. This poses developers building offline web applications for complex challenges: traditional eager data replication strategies are not fit for synchronizing mobile data, because web applications can go offline anytime and generate data while being offline. Fortunately the literature on mobile data replication offers solutions for doing lazy data replication instead and proposes algorithms for automatically detecting and resolving the synchronization conflicts that may occur during lazy replication. In this thesis we attempt to optimize these replication and reconciliation solutions for use within the context and constraints of offline web applications. Our benchmarks show that the network load of synchronizing conflicting data updates can be reduced and that the memory footprint of recording local data updates can be decreased. In addition we propose an eager conflict resolution strategy and explore whether it better fits the constraints of offline web applications than the existing solutions. We provide two different implementations of this strategy and compare them in terms of performance overhead and the average number of conflicts they successfully resolve.