Sharing with a Difference: Realizing Service-Based SaaS Applications with Runtime Sharing and Variation in Dynamic Software Product Lines

A single-instance multi-tenant (SIMT) SaaS application enables a SaaS provider to achieve economies of scale through runtime sharing. However, runtime sharing can make tenant-specific variations difficult to achieve in such an application. In this paper, we propose an approach to realizing SIMT SaaS applications, which is based on Dynamic Software Product Lines (DSPL) and supports runtime sharing and variation. With the collaboration among a subset of services as the unit of composition, the commonality among the tenants' requirements is realized in the DSPL architecture by sharing collaboration units, and their variability is realized by composing different collaboration units, all at runtime. In addition, we adopt a feature-based high-level representation of the commonality and variability between the tenants' requirements to facilitate the runtime creation and reconfiguration of their application variants. We compare our approach with two alternative approaches in terms of development effort and degree of sharing. We further quantify the runtime overhead incurred by our multi-tenancy support.