Introduction

Cloud computing has been gaining momentum as a promising IT solution specially for enabling ubiquitous, convenient, and on-demand accesses to a shared pool of configurable computing resources. Businesses of all sizes nowadays leverage cloud services for conducting their major operations (e.g., web service, inventory management, customer service, etc.). Based on the way services are provided, cloud computing has been divided into different categories such as infrastructure as a service (IaaS), platform as a service (PaaS), and software as a service (SaaS). In most of these categories, there exist at least three main stakeholders: cloud service providers, tenants and their users. A cloud service provider owns a significant amount of computational resources, e.g., servers, storage, and networking, and offers different paid services (e.g., IaaS, PaaS, etc.) to its customers by utilizing this pool of resources. Usually, cloud tenants are different companies or departments within a company. A tenant, the direct customer of cloud providers, enjoys the ad hoc and elastic (i.e., allocating/deprovisioning based on demands) nature of cloud in utilizing the shared pool of resources for conducting its necessary operations. As a member of a cloud tenant, a user mainly avails different services offered by a tenant. Thus, by providing a dynamic (i.e., ever changing) and a measured service (i.e., “pay as you go”) to its users and tenants, cloud computing has become a popular choice for diverse business models in recent years.