FigureVI.4shows the different values obtained for the loss in profit and the number of cancelled jobs with respect to the number of affected resources. For those experiments, the provider and the client expected utility are equal to 0.6 and 0.1, respectively.
We notice that the loss in profit (with and without renegotiation) and the number of cancelled jobs (without renegotiation) increase when the number of affected resources increases. Further, when the unexpected event affects many VMs, the number of rescheduled jobs increases which lead to a potentially increased number of cancelled jobs. Consequently, the total loss in profit will increase. In FigureVI.4(b), the number of cancelled jobs is equal to zero, regardless of the number of resources. This is because, in our configuration, we generate clients whose jobs are highly business-critical. So the clients always accept the renegotiation requests.
Figure VI.4: Impact of variation of number of resources
For the three experiments, we conclude that: 1) our approach performs better than the basic one in terms of profit and the number of cancelled jobs when the clients’ jobs are highly business- critical (low expected client utility); and 2) the performance of our approach tends toward the basic one when the clients have jobs that are less business-critical (when the clients’ expected utility is high). Thus in the second case, the clients do not accept a renegotiation, and prefer to enforce the initial SLA.
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Conclusion
In this chapter, we have described an SLA renegotiation-based approach to proactively handle SLA violations. The renegotiation process is based on the interaction between negoBusiness agent (representing the business provider) and business provider’s provisioning modules (Sched- ule manager, VM provisioner, Monitor). When detecting an unexpected event by the monitor, the business provider may take rescheduling actions to avoid SLA violation. We proposed an algorithm to select the best rescheduling option aiming to minimize the loss in profit and the number of cancelled jobs. The decision-making strategies are based on a utility function for the business provider and scheduling information generated by the rescheduling option chosen before renegotiation. The resulting decision-making model makes possible a win-win situation (ensuring continuity of service and minimizing SLA penalties costs). The experimental evalua- tion demonstrates the benefit of an SLA renegotiation approach as compared with enforcing the original SLA.
Conclusions and Future Work
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Contributions and Research Summary
The cloud market is nowadays a complex environment where business providers need to max- imize their monetary profit and end-users look for the most efficient services with the lowest prices. For efficient cloud provisioning, both providers and users should be satisfied in spite of their conflicting needs. Negotiation is an appealing solution to solve conflicts and enable reach- ing satisfactory agreements. However, to be efficient, the negotiation should consider the cloud provisioning properties (e.g., two interaction levels) and complexities related to dynamicity (e.g., resource availability variation, dynamic pricing) which impact highly the success of the negotia- tion.
Automated negotiation for an efficient cloud provisioning represents a major challenge that is not adequately treated despite the several existing researches. In order to address these challenges, this thesis provides several novel contributions:
• The negotiation-based framework applied to cloud provisioning
In order to build a negotiation framework suitable for cloud provisioning, we have first pro- posed a generic negotiation-based provisioning process showing the interaction between the negotiation and other provisioning activities. Then, we propose a generic negotiator model able to act on behalf of any cloud actor (end-user, business provider, resource provider) and can be used for any negotiation scenario. That model was instantiated among cloud layers resulting in a multi-layer and dynamic negotiation framework for cloud provisioning. What makes our framework differs from others is the fact that it considers cloud provi- sioning properties (multi-layer, dynamic provisioning context).
• Bilateral negotiation for an efficient SaaS application provisioning
For an efficient application provisioning that satisfies end-users and that optimizes business provider’s profit, we have enhanced an existing provisioning approach with negotiation ca- pabilities. The negotiation is carried out between end-users and a business provider. When
it is not possible to schedule the user’s request, the business provider tries to find an alter- native schedule satisfying both parties. The alternative schedules are generated through the communication with other provisioning modules such as the admission control, sched- uler and VM provisioner. We have proposed two decision-making strategies that can be followed according to the business provider’s goal (i.e., preferences).
In contrast to existing SaaS negotiation approaches, our approach is based on the commu- nication with the other provisioning modules in order to optimize business provider’s profit and maximize customer satisfaction. Furthermore, our approach differs from existing pro- visioning approaches by the fact that it considers SLA negotiation between end-users and the business provider in order to bring more flexibility to the provisioning process. • Adaptive and concurrent negotiation for efficient SaaS application provisioning
Due to the gap between the users’ requirements and the business provider’s capabilities at negotiation time, the negotiation may not reach a compromise. So, in order to maximize the number of clients, we have proposed an adaptive and concurrent negotiation approach as an extension to the bilateral one previously described. We have proposed to harness the workload changes in terms of resource availability and pricing in order to renegotiate simultaneously with non-accepted users. The renegotiation is launched when there is a change in the elements considered in the first negotiation. The proposed renegotiation decision-making strategy aims to maximize resource utilization and also customer satis- faction.
Our proposed approach differs from existing ones by the fact that it considers renegotiation before SLA establishment according to workload changes in terms of resource availability and pricing.
• Proactive renegotiation for an efficient SaaS provisioning
In order to handle potential SLA violation, we have proposed a proactive renegotiation approach after SLA establishment. When detecting an unexpected event by the monitor, the business provider may take rescheduling actions to avoid SLA violation. We proposed an algorithm to select the best rescheduling option aiming to minimize the loss in profit and the number of cancelled jobs. The decision-making strategies are based on scheduling information generated by the rescheduling option chosen before renegotiation. The re- sulting decision-making model makes possible a win-win situation (ensuring continuity of service and minimizing SLA penalties costs). Our proposed approach differs from existing ones by the fact that it proposes a concrete renegotiation decision-making model for SaaS provisioning aiming to minimize the loss in profit and ensure the continuity of the service.
Conclusions and Future Work
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Future Directions
Besides the aforementioned contributions, several perspectives are still to be investigated in order to improve our work. In what follows, we present short and long-term perspectives that extend and enhance our work.