Performance , Availability and Cost of Self - Adaptive Internet Services

Although distributed services provide a means for supporting scalable Internet applications, their ad-hoc provisioning and configuration pose a difficult tradeoff between service performance and availability. This is made harder as Internet service workloads tend to be heterogeneous, and vary over time in amount of concurrent clients and in mixture of client interactions. This chapter presents an approach for building self-adaptive Internet services through utility-aware capacity planning and provisioning. First, an analytic model is presented to predict Internet service performance, availability and cost. Second, a utility function is defined and a utility-aware capacity planning method is proposed to calculate the optimal service configuration which guarantees SLA performance and availability objectives while minimizing functioning costs. Third, an adaptive control method is proposed to automatically apply the optimal configuration to the Internet service. Finally, the proposed model, capacity planning and control methods are implemented and applied to an online bookstore. The experiments show that the service successfully self-adapts to both workload mix and workload amount variations, and present significant benefits in terms of performance and availability, with a saving of resources underlying the Internet service. INTRODUCTION A challenging issue in management of distributed Internet services tems from the conflicting goals of, on the one hand, high performance and availability, and on the other hand, low cost and resource consumption. In the limit, high performance and availability can be achieved by assigning all available machines in a data center to an Internet service. Symmetrically, it is possible to build a very-low cost Internet service by allocating very few machines, which induces bad performance and data center downtime. Between these two extremes, there exists a configuration such that distributed Internet services achieve a desirable level of service performance and availability while cost is minimized. This chapter precisely addresses the problem of determining this optimal configuration, and automatically applying it to build a self-adaptive Internet service. The chapter describes a capacity planning method for distributed Internet services that takes into account performance and availability constraints of services. We believe that both criteria must be taken into account collectively. Otherwise, if capacity planning is solely performance-oriented, for instance, this may lead to situations where 99% of service clients are rejected and only 1% of clients are serviced with a guaranteed performance. To our knowledge, this is the first proposal for capacity planning and control of distributed Internet services that combines performance and availability objectives. To do so: