Akhil Sahai

Automated SLA Monitoring for Web Services

SLA monitoring is difficult to automate as it would need precise and unambiguous specification and a customizable engine that collects the right measurement, models the data and evaluates the SLA at certain times or when certain events happen. Also most of the SLA neglect client side measurement or restrict SLAs to measurements based only on server side. In a cross-enterprise scenario like web services it will be important to obtain measurements at multiple sites and to guarantee SLAs on them. In this article we propose an automated and distributed SLA monitoring engine.

SLA Decomposition: Translating Service Level Objectives to System Level Thresholds

In todays complex and highly dynamic computing environments, systems/services have to be constantly adjusted to meet service level agreements (SLAs) and to improve resource utilization, thus reducing operating cost. Traditional design of such systems usually involves domain experts who implicitly translate service level objectives (SLOs) specified in SLAs to system-level thresholds in an ad-hoc manner. In this paper, we present an approach that combines performance modeling with performance profiling to create models that translate SLOs to lower-level resource requirements for each system involved in providing the service. Using these models, the process of creating an efficient design of a system/service can be automated, eliminating the involvement of domain experts. We demonstrate that our approach is practical and that it can be applied to different applications and software architectures. Our experiments show that for a typical 3-tier e-commerce application in a virtualized environment the SLAs can be met while improving CPU utilization up to 3 times.

Automated policy-based resource construction in utility computing environments

A utility environment is dynamic in nature. It has to deal with a large number of resources of varied types, as well as multiple combinations of those resources. By embedding operator and user level policies in resource models, specifications of composite resources may be automatically generated to meet these multiple and varied requirements. The paper describes a model for automated policy-based construction of complex environments. We pose the policy problem as a goal satisfaction problem that can be addressed using a constraint satisfaction formulation. We show how a variety of construction policies can be accommodated by the resource models during resource composition. We are implementing this model in a prototype that uses CIM as the underlying resource model and exploring issues that arise as a result of that implementation.

Web Services Management Network: an overlay network for federated service management

We introduce the architecture, object model, components, and protocols of a management overlay for federated service management, called Web Services Management Network (WSMN). WSMN targets management of Web services that interact across administrative domains, and therefore typically involves multiple stakeholders (examples are business-to-business, service provider interconnections, help desks). The architecture is based on (implicit) SLA to formalize relations across domains. It relies on a network of communicating service intermediaries, each such intermediary being a proxy positioned between the service and the outside world. WSMN also exchanges control information to agree on what to monitor, where to monitor, and whom to provide visibility.

Quartermaster - a resource utility system

Utility computing is envisioned as the future of enterprise IT environments. Achieving utility computing is a daunting task, because enterprise users have diverse and complex needs. In this paper we describe quartermaster, an integrated set of tools that addresses some of these needs. Quartermaster supports the entire lifecycle of computing tasks - including design, deployment, operation, and decommissioning of each task. Although individual components of this lifecycle have been addressed in earlier work, quartermaster integrates them in a unified framework using model-based automation. All tools within quartermaster are integrated using models based on the common information model (CIM), an industry-standard model from the distributed management task force (DMTF). The paper discusses the quartermaster implementation, and describes two case studies using quartermaster.

A state-space approach to SLA based management

Large complex systems (such as Enterprise systems) are often composed of several interacting, independent components. In many such systems, although the behavior of the constituent components is well characterized, the behavior that results from interaction between such components is more or less intractable; making it hard for the administrators to efficiently manage the system in conformance with the service level agreements or the SLAs. This paper presents an approach for deriving component-level objectives from system-level objectives or agreements, which if conformed to, imply conformance to the higher-level SLA. Our approach partitions the systempsilas state-space into homogeneous sub-spaces, creates micro-models for such subspaces, and then uses such micro-models to translate the higher-level objectives to component-level objectives. We have implemented a system, termed Pranaali, for evaluating our approach in realistic settings.

Translating Service Level Objectives to lower level policies for multi-tier services

Service providers and their customers agree on certain quality of service guarantees through Service Level Agreements (SLA). An SLA contains one or more Service Level Objectives (SLO)s that describe the agreed-upon quality requirements at the service level. Translating these SLOs into lower-level policies that can then be used for design and monitoring purposes is a difficult problem. Usually domain experts are involved in this translation that often necessitates application of domain knowledge to this problem. In this article, we propose an approach that combines performance modeling with regression analysis to solve this problem. We demonstrate that our approach is practical and that it can be applied to different n-tier services. Our experiments show that for a typical 3-tier e-commerce application in a virtualized environment, the SLA can be met while improving CPU utilization by up to 3 times.

Categorization and Optimization of Synchronization Dependencies in Business Processes

The current approach for modeling synchronization in business processes relies on sequencing constructs, such as sequence, parallel etc. However, sequencing constructs obfuscate the true source of dependencies in a business process. Moreover, because of the nested structure and scattered code that results from using sequencing constructs, it is hard to add or delete additional constraints without over-specifying necessary constraints or invalidating existing ones. We propose a dataflow programming approach in which dependencies are explicitly modeled to guide activity scheduling. We first give a systematic categorization of dependencies: data, control, service and cooperation. Each dimension models dependency from its own point of view. Then we show that dependencies of various kinds can be first merged and then optimized to generate a minimal dependency set, which guarantees high concurrency and minimal maintenance cost for process execution.

Automated generation of resource configurations through policies

Resource management systems have been attempting to undertake automated configuration management. Automated configuration management involves considering user requirements, operator constraints and technical constraints of the system to create a suitable configuration, and to create a workflow to deploy it. In this article we propose a policy-based model that we have used for automating these configuration management aspects.

Message tracking in SOAP-based Web services

As Web services become more prevalent, the nature of electronic transactions on the Internet changes from simple browser-to-business clicks to an orchestrated flow of messages between cross-enterprise services. Consequently, more than one service could participate in the federated execution of a single transaction. In such cases, the problem of end-to-end management becomes very important. The inherent cross-enterprise or distributed nature of the problem, security of information exchanged, and the complexity in correlating related messages into a single transaction make this problem challenging. We present an approach to track and correlate messages between Web services that are part of a single transaction. We do this by proposing management information exchange agreements between service providers, and a distributed message tracking algorithm that is executed within each service provider. We also explain the techniques for realizing our solution in the case of Web services that communicate using the Simple Object Access Protocol (SOAP).