Policy-Driven Middleware for Multi-Tenant SaaS Services Configuration

The multi-tenancy architecture allows software-as-a-service applications to serve multiple tenants with a single instance. This is beneficial as it leverages economies of scale. However, it does not cope with the specificities of each tenant and their variability; notably, the variability induced in the required quality levels that differ from a tenant to another. Hence, sharing one single instance hampers the fulfillment of these quality levels for all the tenants and leads to service level agreement violations. In this context, this article proposes a policy-driven middleware that configures the service according to the non-functional requirements of the tenants. The adopted approach combines software product lines engineering and model driven engineering principles. It spans the quality attributes lifecycle, from documenting them to annotating the service components with them as policies, and it enables dynamic configuration according to service level agreements terms of the tenants.