Girish Chafle

Decentralized orchestration of composite web services

Web services make information and software available programmatically via the Internet and may be used as building blocks for applications. A composite web service is one that is built using multiple component web services and is typically specified using a language such as BPEL4WS or WSIPL. Once its specification has been developed, the composite service may be orchestrated either in a centralized or in a decentralized fashion. Decentralized orchestration offers performance improvements in terms of increased throughput and scalability and lower response time. However, decentralized orchestration also brings additional complexity to the system in terms of error recovery and fault handling. Further, incorrect design of a decentralized system can lead to potential deadlock or non-optimal usage of system resources. This paper investigates build time and runtime issues related to decentralized orchestration of composite web services. We support our design decisions with performance results obtained on a decentralized setup using BPEL4WS to describe the composite web services and BPWS4J as the underlying runtime environment to orchestrate them.

Synthy: A system for end to end composition of web services

The demand for quickly delivering new applications is increasingly becoming a business imperative today. However, application development is often done in an ad hoc manner resulting in poor reuse of software assets and longer time-to-delivery. Web services have received much interest due to their potential in facilitating seamless business-to-business or enterprise application integration. A web service composition system can help automate the process, from specifying business process functionalities, to developing executable workflows that capture non-functional (e.g. Quality of Service (QoS)) requirements, to deploying them on a runtime infrastructure. Intuitively, web services can be viewed as software components and the process of web service composition similar to software synthesis. In addition, service composition needs to address the build-time and runtime issues of the integrated application, thereby making it a more challenging and practical problem than software synthesis. However, current solutions based on business web services (using WSDL, BPEL, SOAP, etc.) or semantic web services (using ontologies, goal-directed reasoning, etc.) are both piecemeal and insufficient. We formulate the web service composition problem and describe the first integrated system for composing web services end to end, i.e., from specification to deployment. The proposed solution is based on a novel two-staged composition approach that addresses the information modeling aspects of web services, provides support for contextual information while composing services, employs efficient decoupling of functional and non-functional requirements, and leads to improved scalability and failure handling. We also present Synthy, a prototype of the service composition system, and demonstrate its effectiveness with the help of an application scenario from the telecom domain.

Understanding approaches for web service composition and execution

Web services have received much interest due to their potential in facilitating seamless business-to-business or enterprise application integration. Of particular interest is the Web Service Composition and Execution (WSCE) process - the creation of a workflow that realizes the functionality of a new service and its subsequent deployment and execution on a runtime environment. A significant number of solutions have been proposed in the literature for composition and execution of web services. However, in order to choose a suitable technique for an application scenario, one needs to systematically analyze the strengths and weaknesses of each of these solutions. To this end, we present an analysis that includes formalization of the WSCE process, a classification of existing solutions into four distinct categories (approaches), and an in-depth evaluation of these approaches. Our evaluation is based on multiple metrics that we deem critical for a WSCE system, e.g. composition effort, composition control, and ability to handle failures. We also present an application of this analysis to three different scenarios.

Adaptation inWeb Service Composition and Execution

Web services simplify enterprise application integration by facilitating reuse of existing components for creating new services. In a dynamic environment, it is imperative to design a Web service composition and execution (WSCE) system that adapts to failure of component services or changes in their QoS offerings. In this paper, we motivate a staged approach for adaptive WSCE (A-WSCE) that cleanly separates the functional and non-functional requirements of a new service, and enables different environmental changes to be absorbed at different stages of composition and execution. We use Synthy, a prototype service creation environment, to implement our solution and demonstrate its effectiveness

Orchestrating composite Web services under data flow constraints

A composite service is typically specified using a language such as BPEL4WS and orchestrated by a single coordinator node in a centralized manner. The coordinator receives the client request, makes the required data transformations and invokes the component Web services as per the specification. However, in certain scenarios businesses might want to impose restrictions on access to the data they provide or the source from which they can accept data. Centralized orchestration can lead to violation of these data flow constraints as the central coordinator has access to the input and output data of all the component Web services. In many cases existing methods of data encryption and authentication are not sufficient to handle such constraints. These data flow constraints, thus, present obstacles for composite Web service orchestration. In this paper we propose a solution for orchestrating composite Web services under data flow constraints. The solution is based on decentralized orchestration, in which a composite Web service is broken into a set of partitions, one partition per component Web service. To overcome data flow constraints, each partition is executed within the same domain as the corresponding component Web service and hence, has the same access rights. However, there are, in general, many ways to decentralize a composite Web service. We apply a rule based filtering mechanism to choose a set of partitions that does not violate the specified dataflow constraints.

An Integrated Development Environment for Web Service Composition

Web services provide an instantiation of the loosely coupled service-oriented architecture and facilitate the process of enterprise application integration by encapsulating information, software, and other resources. However, to exploit the true potential of web services, it is critical to develop technologies and tools for composing new services from existing ones. While numerous composition approaches have been developed in the past, very little has been done towards tooling. What is clearly lacking is an Integrated Development Environment (IDE) to ease the process of composition, thereby reducing development time and integration efforts. In this paper, we build on our previous work on service composition, and present an IDE for end-to-end composition of web services. We elaborate on the design of the IDE, describe its integration with existing technologies, and discuss its usability based on the findings of a user survey.

Handling faults in decentralized orchestration of composite web services

Composite web services can be orchestrated in a decentralized manner by breaking down the original service specification into a set of partitions and executing them on a distributed infrastructure. The infrastructure consists of multiple service engines communicating with each other over asynchronous messaging. Decentralized orchestration yields performance benefits by exploiting concurrency and reducing the data on the network. Further, decentralized orchestration may be necessary to orchestrate certain composite web services due to privacy and data flow constraints. However, decentralized orchestration also results in additional complexity due to absence of a centralized global state, and overlapping or different life cycles of the various partitions. This makes handling of faults arising from composite service partitions or from the failure of component web services, a challenging task. In this paper we propose a mechanism for handling faults in decentralized orchestration of composite web services. The mechanism includes a strategy for placement of fault handlers and compensation handlers, and schemes for fault propagation and fault recovery. The mechanism is designed to maintain the semantics of the original specification while ensuring minimal overheads.

Workload Characterization for Capacity Planning and Performance Management in IaaS Cloud

Effective characterization of workload could be used to drive Capacity Planning and Performance Management in IaaS Cloud. There are different workload metrics (e.g. CPU, memory usage, throughput, response time) which could be modeled along with relationships between them. Similarly, we could model relationships across a set of workloads. Analyzing and characterizing this would enable decision making for various scenarios such as migration, re-provisioning, load balancing, resource management, initial placement. In this paper, we study workload running in IaaS cloud and categorize into patterns, based on their behavioral characteristics. We define different types of behavioral patterns and outline statistical techniques to be used in determining these patterns. We present initial results for development workload data collected in the lab.

Improving Performance of CompositeWeb Services Over a Wide Area Network

Performance of distributed applications over a wide area network (WAN) has remained an important issue as WAN conditions change over time. Networking community has employed various approaches to improve application performance by adapting to changes in WAN conditions. Composite web services with components distributed over a WAN pose similar performance problems, however, with a different set of challenges and opportunities to improve. With their unique architecture, these composite web services can be partitioned and orchestrated in a decentralized fashion on a distributed infrastructure. In this paper, we investigate how different topologies generated by decentralized orchestration are affected differently by variations in WAN conditions. We present a system that exploits this and adapts to changes in WAN conditions. The system monitors the availability of network bandwidth, evaluates its effect on the performance of each topology using a performance model based on bandwidth availability, and then selects the optimal topology at runtime. The results from our simulation show that the adaptive system improves performance.

A system for providing differentiated QoS in retail banking

In todays services driven economic environment, it is imperative for organizations to provide better quality service experience to differentiate and grow their business. Customer satisfaction (C-SAT) is the key driver for retention and growth in Retail Banking. Wait time, the time spent by a customer at the branch before getting serviced, contributes significantly to C-SAT. Due to high footfall, it is improbable to improve the wait time of every customer walking in the branch. Therefore, banks in developing countries are strategically looking to segment its customers and services and offer differentiated QoS based service delivery. In this work, we present a system for customer segmentation, and scheduling based on historic value of the customer and characteristics of current service request. We describe the system and give mathematical formulation of the scheduling problem and the associated heuristics. We present results and experience of deployment of this solution in multiple branches of a leading bank in India.