Aleksander Slominski

Programming the Grid: Distributed Software Components, P2P and Grid Web Services for Scientific Applications

Computational Grids [17,25] have become an important asset in large-scale scientific and engineering research. By providing a set of services that allow a widely distributed collection of resources to be tied together into a relatively seamless computing framework, teams of researchers can collaborate to solve problems that they could not have attempted before. Unfortunately the task of building Grid applications remains extremely difficult because there are few tools available to support developers. To build reliable and re-usable Grid applications, programmers must be equipped with a programming framework that hides the details of most Grid services and allows the developer a consistent, non-complex model in which applications can be composed from well tested, reliable sub-units. This paper describes experiences with using a software component framework for building Grid applications. The framework, which is based on the DOE Common Component Architecture (CCA) [1,2,3,8], allows individual components to export function/service interfaces that can be remotely invoked by other components. The framework also provides a simple messaging/event system for asynchronous notification between application components. The paper also describes how the emerging Web-services [52] model fits with a component-oriented application design philosophy. To illustrate the connection between Web services and Grid application programming we describe a simple design pattern for application factory services which can be used to simplify the task of building reliable Grid programs. Finally we address several issues of Grid programming that better understood from the perspective of Peer-to-Peer (P2P) systems. In particular we describe how models for collaboration and resource sharing fit well with many Grid application scenarios.

Requirements for and Evaluation of RMI Protocols for Scientific Computing

Distributed software component architectures provide promising approach to the problem of building large scale, scientific Grid applications [18]. Communication in these component architectures is based on Remote Method Invocation (RMI) protocols that allow one software component to invoke the functionality of another. Examples include Java remote method invocation (Java RMI)[25] and the new Simple Object Access Protocol (SOAP) [15]. SOAP has the advantage that many programming languages and component frameworks can support it. This paper describes experiments showing that SOAP by itself is not efficient enough for large scale scientific applications. However, when it is embedded in multi-protocol RMI framework, SOAP can be effectively used as a universal control protocol, that can be swapped out by faster, more special purpose protocols when large data transfer speeds are needed.

A Benchmark Suite for SOAP-based Communication in Grid Web Services

The convergence of Web services and grid computing has promoted SOAP, a widely used Web services protocol, into a prominent protocol for a wide variety of grid applications. These applications differ widely in the characteristics of their respective SOAP messages, and also in their performance requirements. To make the right decisions, an application developer must thus understand the complex dependencies between the SOAP implementation and the application. We propose a standard benchmark suite for quantifying, comparing, and contrasting the performance of SOAP implementations under a wide range of representative use cases. The benchmarks are defined by a set of WSDL documents. To demonstrate the utility of the benchmarks and to provide a snapshot of the current SOAP implementation landscape, we report the performance of many different SOAP implementations (gSOAP, AxisJava, XSUL and bSOAP) on the benchmarks, and draw conclusions about their current performance characteristics.

Performance comparison of security mechanisms for grid services

Security is one of the most important features for grid services. There are several specifications used to add security to grid services, and some of them have been implemented and are in use. However, since most of the security mechanisms involve slow XML manipulations, adding security to grid services introduces a big performance penalty. In this paper, we introduce various security mechanisms and compare their features and performance. Our evaluation shows that transport level security (SSL) is faster than message level security, and should be used if there is no special requirement to use message level security. For message level security, WS-SecureConversation is generally fast, but has a scalability problem.

Business Provenance --- A Technology to Increase Traceability of End-to-End Operations

Todays enterprise applications span multiple systems and organizations, integrating legacy and newly developed software components to deliver value to business operations. Often business processes rely on human activities that may not be predicted in advance, and information exchange is heavily based on e-mails or attachments where the content is unstructured and needs discovery. Visibility of such end-to-end operations is required to manage compliance and business performance. Hence, it becomes necessary to develop techniques for tracking and correlating the relevant aspects of business operations as needed without the cost and overhead of a fully fledged data and process reengineering. Our business provenance solution provides a generic data model and middleware infrastructure to collect and correlate information about how data was produced, what resources were involved and which tasks were executed. Business provenance gives the flexibility to selectively capture information required to address a specific compliance or performance goal. Additionally, a powerful correlation mechanism yields a representation of the end-to-end operation that puts each business artifact into the right context, for example, to detect situations of compliance violations and find their root causes.

Apache airavata: a framework for distributed applications and computational workflows

In this paper, we introduce Apache Airavata, a software framework to compose, manage, execute, and monitor distributed applications and workflows on computational resources ranging from local resources to computational grids and clouds. Airavata builds on general concepts of service-oriented computing, distributed messaging, and workflow composition and orchestration. This paper discusses the architecture of Airavata and its modules, and illustrates how the software can be used as individual components or as an integrated solution to build science gateways or general-purpose distributed application and workflow management systems.

Toward characterizing the performance of SOAP toolkits

The SOAP protocol underpins Web services as the standard mechanism for exchanging information in a distributed environment. The XML-based protocol offers advantages including extensibility, interoperability, and robustness. The merger of Web services and grid computing promotes SOAP into a standard protocol for the large-scale scientific applications that computational grids promise to support, further elevating the protocols importance and requiring high-performance implementations. Various SOAP implementations differ in their implementation language, invocation model and API, and supported performance optimizations. In this paper we compare and contrast the performance of widely used SOAP toolkits and draw conclusions about their current performance characteristics. We also provide insights into various design features that can lead to optimized SOAP implementations. The SOAP implementations included in our study are gSOAP 2.4, AxisC++ CVS May 28, AxisJava 1.2, .NET 1.1.4322 and XS0AP4/XSUL 1.1.

WS-Messenger: a Web services-based messaging system for service-oriented grid computing

A Web services-based publish/subscribe system has the potential to create an Internet scale interoperable event notification system which is important for grid computing as it evolves a service-oriented architecture. WS-Messenger is designed to be a Web services-based message broker that can decouple event producers and event consumers and achieve scalable, reliable and efficient message delivery. In this paper, we discuss some challenges that are unique to Web services-based publish/subscribe systems and the key features that distinguish WS-Messenger from other existing message brokers. We then present the architecture and the technology used in WS-Messenger. Performance tests indicate WS-Messenger performs better than the WS-Notification implementation in Globus Toolkit 4 (GT4) and it can be used as a complement to GT4 to improve its scalability. We lastly describe its application to grid workflow orchestration in the LEAD project.

Merging the CCA component model with the OGSI framework

The most important recent development in Grid systems is the adoption of the Web Services model as its basic architecture. The result is called the Open Grid Services Architecture (OGSA). This paper describes a component framework for distributed Grid applications that is consistent with that model. The framework, called XCAT, is based on the U.S. Department of Energy Common Component Architecture (CCA) but with an implementation based on the standard Web Services stack. Using this framework, an application programmer can compose an application from a set of distributed components. The result is a set of Web Services that collectively represent the executing application instance. This paper describes the basic architecture of XCAT and the design issues to be considered for a component to serve as both a CCA and Open Grid Service Infrastructure (OGSI) service.

Building Grid Portal Applications From a Web Service Component Architecture

This work describes an approach to building Grid applications based on the premise that users who wish to access and run these applications prefer to do so without becoming experts on Grid technology. We describe an application architecture based on wrapping user applications and application workflows as Web services and Web service resources. These services are visible to the users and to resource providers through a family of Grid portal components that can be used to configure, launch, and monitor complex applications in the scientific language of the end user. The applications in this model are instantiated by an application factory service. The layered design of the architecture makes it possible for an expert to configure an application factory service with a custom user interface client that may be dynamically loaded into the portal.