Integrating dynamic scalability into the OpenSimulator framework

Abstract OpenSimulator, when configured in grid mode, is highly scalable and places no restriction on the number of running OpenSimulator instances, often called Simulator, or the number of regions assigned to a simulator. However, the current implementation employs static configuration which either results in under-use of resources or restricts system capacity. This is due to the lack of an expansion and contraction model which would allocate resources purely based on load. This paper introduces scalability features into OpenSimulator based on our expansion and contraction models that use a hybrid grid infrastructure. The enhanced system takes dynamic decisions to add additional resources and reallocate regions as load increases, until each simulator is hosting a single unit region. We use a merge strategy, in which a simulator integrates its load back directly with the parent simulator if the current load decreases significantly. It has been verified using a 4-region test world for both expansion and contraction. Different patterns of player distribution are used to illustrate the benefits and limitations of this new feature. We identify the existing OpenSimulator components needed to incorporate this exciting feature. Further, we introduce an improved region removal strategy to significantly reduce the time to reallocate a region and hence to enhance the interactive user experience.