5. Conclusion
A workflow is a logical sequence of the dependent tasks. Numerous studies have been conducted about the workflow scheduling in the cloud computing which utilize heuristics and metaheuristics algorithms to obtain the approximated solutions.
This paper provided a comprehensive analysis of the workflow scheduling schemes proposed for the cloud computing environment. These schemes are classified based on the type of the algorithm utilized in the workflow scheduling and their various objectives and properties are analyzed and compared. Also, various factors which are considered in each scheduling scheme are highlighted, and the limitations and advantages of the scheduling schemes are specified.
One of the issues which have less been addressed in most workflow scheduling schemes is the concept of the secure scheduling. Considering the ever increasing security attacks against the cloud environment, various attacks have been presented in the literature which target the cloud schedulers and other cloud components such as the VMs. As a result, in the future research and studies, the security and trust-related concept should be integrated in the cloud scheduling to differentiate the workflow requests issued by the attackers and the trusted cloud users. Thus, regarding the security vulnerabilities of the cloud environment, cloud scheduler should be empowered with the secure algorithms to prevent or thwart various attacks such as the cloud internal denial of the service attacks, the VM sprawl attacks, the VM neighbor attacks, the VM migrate and escape attacks and so on.
