Using Mobile Extensions to Support Disconnected Services

This paper examines the design and implementation of mobile extensions, a distributed operating system abstraction for supporting disconnected access to dynamic distributed services. The goal of mobile extensions is to make it as easy for service providers to deploy services that make use of caching, hoarding, asynchronous messaging, and application-level adaptation to cope with mobility, network failures, and server failures. We identify resource management as a crucial problem in this environment and develop a novel popularity-based resource management policy and demonstrate that under web service workloads it allocates resources nearly as efficiently as traditional schedulers, while under workloads with more aggressive resource users, it provides much stronger performance isolation. Overall, we find that for the four web service workloads we study, mobile extensions can reduce failures by as much as a factor of 5.9 to a factor of 16.7 for those applications able to provide tolerable service when disconnected.