Services Composition in Multi-cloud Environments using the Skyline Service Algorithm

The rapid growth of cloud environments has led to the expansion of resources that offer a variety of services. The opertions of the services are usually very simple and may not satisfy the  complex needs of the user, hence there is a need for a combination of these services that can fulfill the user's requirements. Most of the service composition methods in cloud environments assume that the involved services came from one cloud, and this is unrealistic because other clouds may provide more relevant services. The challenges in composition services distributed in multi-cloud environments include increased cost and a reduction in its speed due to the increasing number of services, providers, and clouds; so, in order to overcome these challenges, the number of providers and participating clouds must be reduced. This study used the Skyline service algorithm to compose services in multi-cloud environments, which examined all the clouds during the service composition process. The proposed method can provide an applicable composition service to the user with the lowest communication cost by considering the number of clouds and by using fewer providers. The Skyline algorithm involves two steps. In the first one, the best composition in a cloud environment is selected among all the possible providers by considering the number of providers and the communication time. In the second step, the Skyline algorithm is used to create all the possible compositions in a multi-cloud environment. Parameters such as fewer clouds and shorter communication times between the clouds are selected. The results show that the proposed method can find the composition with the least number of clouds, the lowest cost, and has the lowest calculation time. It can be said that the Skyline makes it possible to select a suitable composition of user-requested services in a multi-cloud environment.