An Exploratory Study of Architectural Style and Effort Estimation for Multi-Tenant Microservices-Based Software as a Service (SaaS)

Service Provider evolving to a multi-tenant Software as a Service (SaaS) model seeks to minimise effort and cost with a shared application environment. There are existing research techniques to fit the service in a shared environment; many require specific technology to be implemented. This requirement causes a challenge for Service Providers that already commit to a technology stack to adopt. The actual development efforts are also not revealed or discussed in existing works, posing another challenge for Service Providers to estimate efforts for decision-making. In this paper, we propose abstracting these multi-tenant designs in a technology-independent perspective as an architectural style to guide Service Providers in supporting multi-tenants on new or existing technology stacks. We start by reviewing existing works to understand the necessary properties of a multi-tenant architectural style. We then model the proposed architectural style using the UML web engineering approach for a case study of evolving single-tenant web application to support multiple tenants. We record our estimated and actual development efforts and validate them against an existing web effort prediction model. The evaluation results show that our effort estimations are consistent with the web effort prediction model trained from another set of 19 web projects. We hope that a validated web effort prediction model for multi-tenancy to estimate the development efforts early before actual implementation can help Service Providers make development decisions. This paper contributes a multi-tenant architectural style and a validated web effort prediction model for early effort estimation to help decision making. We hope this work can help software architects make an informed decision on designing for multi-tenancy in their web applications and encourage more widespread adoption of multi-tenant designs.