Evaluating Degrees of Multitenancy Isolation: A Case Study of Cloud-Hosted GSD Tools

Multitenancy is an essential cloud computing property where a single instance of an application serves multiple tenants. Multitenancy introduces significant challenges when deploying application components to the cloud due to the demand for different degrees of isolation between tenants. At the very basic degree of isolation, tenants still share application components as much as possible. However, while some components may benefit from low degree of isolation between tenants, others may need a higher degree of isolation, for instance, in a situation where a component is too critical to be shared, or needs to be configured specifically for individual tenants. This paper describes COMITRE (COmponent-based approach to Multitenancy Isolation Through request RE-routing) to empirically evaluate the degree of isolation between tenants enabled by three multitenancy patterns (i.e., shared component, tenant-isolated component, and dedicated component) for cloud-hosted Global Software Development (GSD) tools. We developed a multitenant component for each multitenancy pattern, integrated it within Hudson, and then compared their impact on different tenants. The study revealed among other things that a component deployed based on shared component offers a lower degree of tenant isolation (than tenant-isolated component and dedicated component) when one of the tenants is exposed to a demanding deployment condition (e.g, large instant loads). We also provide some recommendations to guide an architect in implementing multitenancy isolation on a set of GSD tools: Hudson, Subversion and Bugzilla.