Gopi Kandaswamy

Building web services for scientific grid applications

Web service architectures have gained popularity in recent years within the scientific grid research community. One reason for this is that web services allow software and services from various organizations to be combined easily to provide integrated and distributed applications. However, most applications developed and used by scientific communities are not web-service-oriented, and there is a growing need to integrate them into grid applications based on service-oriented architectures. In this paper, we describe a framework that allows scientists to provide a web service interface to their existing applications as web services without having to write extra code or modify their applications in any way. In addition, application providers do not need to be experts in web services standards, such as Web Services Description Language, Web Services Addressing, Web Services Security, or secure authorization, because the framework automatically generates these details. The framework also enables users to discover these application services, interact with them, and compose scientific workflows from the convenience of a grid portal.

Fault Tolerance and Recovery of Scientific Workflows on Computational Grids

In this paper, we describe the design and implementation of two mechanisms for fault-tolerance and recovery for complex scientific workflows on computational grids. We present our algorithms for over-provisioning and migration, which are our primary strategies for fault-tolerance. We consider application performance models, resource reliability models, network latency and bandwidth and queue wait times for batch-queues on compute resources for determining the correct fault-tolerance strategy. Our goal is to balance reliability and performance in the presence of soft real-time constraints like deadlines and expected success probabilities, and to do it in a way that is transparent to scientists. We have evaluated our strategies by developing a Fault-Tolerance and Recovery (FTR) service and deploying it as a part of the Linked Environments for Atmospheric Discovery (LEAD) production infrastructure. Results from real usage scenarios in LEAD show that the failure rate of individual steps in workflows decreases from about 30% to 5% by using our fault-tolerance strategies.

The Open Grid Computing Environments collaboration: Portlets and services for science gateways

We review the efforts of the Open Grid Computing Environments collaboration. By adopting a general three-tiered architecture based on common standards for portlets and Grid Web services, we can deliver numerous capabilities to science gateways from our diverse constituent efforts. In this paper, we discuss our support for standards-based Grid portlets using the Velocity development environment. Our Grid portlets are based on abstraction layers provided by the Java CoG kit, which hide the differences of different Grid toolkits. Sophisticated services are decoupled from the portal container using Web service strategies. We describe advance information, semantic data, collaboration, and science application services developed by our consortium. Copyright

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.

Cooperating services for data-driven computational experimentation

The Linked Environments for Atmospheric Discovery (LEAD) project seeks to provide on-demand weather forecasting. A triad of cooperating services provides the core functionality needed to execute experiments and manage the data. In this article, we focus on three MyLEAD services - the metadata catalog service, notification service, and workflow service - that together form the core services for managing complex experimental meteorological investigations and managing the data products used in and generated during the computational experimentation. We show how the services work together on the users behalf, easing the technological burden on the scientists and freeing them to focus on more of the science that compels them.

On Building Parallel & Grid Applications: Component Technology and Distributed Services

Software Component Frameworks are well known in the commercial business application world and now this technology is being explored with great interest as a way to build large-scale scientific applications on parallel computers. In the case of Grid systems, the current architectural model is based on the emerging web services framework. In this paper we describe progress that has been made on the Common Component Architecture model (CCA) and discuss its success and limitations when applied to problems in Grid computing. Our primary conclusion is that a component model fits very well with a services-oriented Grid, but the model of composition must allow for a very dynamic (both in space and in time) control of composition. We note that this adds a new dimension to conventional service workflow and it extends the “Inversion of Control” aspects of most component systems.

Building Applications from a Web Service based Component Architecture

This chapter describes an approach to building large-scale, distributed applications based on a software component composition model that allows web services to be used as the basic units. The approach extends the Common Component Architecture used in many parallel supercomputer applications, from static composition of directly coupled processes to a system that incorporates mediated workflow between remote services. The system also allows legacy applications to be easily wrapped as a component and executed from a service factory. We motivate the work in terms of a large, distributed application for modeling severe storms. The entire system is based on a three-level architecture with a portal providing the user interface, a set of security and factory service utilities in the middle and the application services and components in the back-end.

Dynamic, Adaptive Workflows for Mesoscale Meteorology

The Linked Environments for Atmospheric Discovery (LEAD) [122] is a National Science Foundation funded1 project to change the paradigm for mesoscale weather prediction from one of static, fixed-schedule computational forecasts to one that is adaptive and driven by weather events. It is a collaboration of eight institutions,2 led by Kelvin Droegemeier of the University of Oklahoma, with the goal of enabling far more accurate and timely predictions of tornadoes and hurricanes than previously considered possible. The traditional approach to weather prediction is a four-phase activity. In the first phase, data from sensors are collected. The sensors include ground instruments such as humidity and temperature detectors, and lightning strike detectors and atmospheric measurements taken from balloons, commercial aircraft, radars, and satellites. The second phase is data assimilation, in which the gathered data are merged together into a set of consistent initial and boundary conditions for a large simulation. The third phase is the weather prediction, which applies numerical equations to measured conditions in order to project future weather conditions. The final phase is the generation of visual images of the processed data products that are analyzed to make predictions. Each phase of activity is performed by one or more application components.

The Open Grid Computing Environments collaboration: portlets and services for science gateways: Research Articles

Web portals are one of the possible ways to access the remote computing resources offered by Grid environments. Since the emergence of the first middleware for the Grid, works have been conducted on delivering the functionality of Grid services on the Web. Many interesting Grid portal solutions have been designed help organize remote access to Grid resources and applications from within Web browsers. They are technically advanced and more and more widely used around the world, resulting in feedback from the community. Some of these user comments concern the flexibility and user-friendliness of the developed solutions. In this paper we present how we addressed the need for a flexible and user-friendly Grid portal environment within the PROGRESS project and how our approach facilitates the use of the Grid within Web portals. Copyright

Building Grid Applications and Portals: An Approach Based on Components, Web Services and Workflow Tools

Large scale Grid applications are often composed a distributed collection of parallel simulation codes, instrument monitors, data miners, rendering and visualization tools. For example, consider a severe storm prediction system driven by a grid of weather sensors. Typically these applications are very complex to build, so users interact with them through a Grid portal front end. This talk outlines an approach based on a web service component architecture for building these applications and portal interfaces. We illustrate how the traditional parallel application can be wrapped by a web service factory and integrated into complex workflows. Additional issues that are addressed include: grid security, web service tools and workflow composition tools. The talk will try to outline several important classes of unsolved problems and possible new research directions for building grid applications.