Onyeka Ezenwoye

RobustBPEL2: Transparent Autonomization in Business Processes through Dynamic Proxies

Web services paradigm is allowing applications to interact with one another over the Internet. BPEL facilitates this interaction by providing a platform through which Web services can be integrated. However, the autonomous and distributed nature of the integrated services presents unique challenges to the reliability of composed services. The focus of our ongoing research is to transparently introduce autonomic behavior to BPEL processes in order to make them more resilient to the failure of partner services. In this work, we present an approach where BPEL processes are adapted by redirecting their interactions with partner services to a dynamic proxy. We describe the generative adaptation process and the architecture of the adaptive BPEL processes and their corresponding proxies. Finally, we use case studies to demonstrate how generated dynamic proxies are used to support self-healing and self-optimization in instrumented BPEL processes

A Proxy-Based Approach to Enhancing the Autonomic Behavior in Composite Services

Web services paradigm is allowing applications to electronically interact with one another over the Internet. The business process execution language (BPEL) takes this interaction to a higher level of abstraction by enabling the development of aggregate Web services. However, the autonomous and distributed nature of the partner services in an aggregate Web service present unique challenges to the reliability of the composite services. In this paper, we present an approach where existing BPEL processes are automatically instrumented, so that when one or more of their partner services do not provide satisfactory service (e.g., because of a service being overwhelmed, crashed, or because of a network outage), the request for service is redirected to a proxy Web service, where the failed or slow services are replaced by substitute services.

Grid service composition in BPEL for scientific applications

Grid computing aims to create an accessible virtual supercomputer by integrating distributed computers to form a parallel infrastructure for processing applications. To enable service-oriented Grid computing, the Grid computing architecture was aligned with the current Web service technologies; thereby, making it possible for Grid applications to be exposed as Web services. The WSRF set of specifications standardized the association of state information with Web services (WS-Resource) while providing interfaces for the management of state data. The Business Process Execution Language (BPEL) is the leading standard for integrating Web services and as such has a natural affinity to the integration of Grid services. In this paper, we share our experience on using BPEL to integrate, create, and manage WS-Resources that implement the factory pattern. To the best of our knowledge, this work is among the handful approaches that successfully use BPEL for orchestrating WSRF-based services and the only one that includes the discovery and management of instances.

Transparent grid enablement of weather research and forecasting

The impact of hurricanes is so devastating throughout different levels of society that there is a pressing need to provide a range of users with accurate and timely information that can enable effective planning for and response to potential hurricane landfalls. The Weather Research and Forecasting (WRF) code is the latest numerical model that has been adopted by meteorological services worldwide. The current version of WRF has not been designed to scale out of a single organizations local computing resources. However, the high resource requirements of WRF for fine-resolution and ensemble forecasting demand a large number of computing nodes, which typically cannot be found within one organization. Therefore, there is a pressing need for the Grid-enablement of the WRF code such that it can utilize resources available in partner organizations. In this paper, we present our research on Grid enablement of WRF by leveraging our work in transparent shaping, GRID superscalar, profiling, code inspection, code modeling, meta-scheduling, and job flow management.

Design and Implementation of a Fault Tolerant Job Flow Manager Using Job Flow Patterns and Recovery Policies

Currently, many grid applications are developed as job flows that are composed of multiple jobs. The execution of job flows requires the support of a job flow manager and a job scheduler. Due to the long running nature of job flows, the support for fault tolerance and recovery policies is especially important. This support is inherently complicated due to the sequencing and dependency of jobs within a flow, and the required coordination between workflow engines and job schedulers. In this paper, we describe the design and implementation of a job flow manager that supports fault tolerance. First, we identify and label job flow patterns within a job flow during deployment time. Next, at runtime, we introduce a proxy that intercepts and resolves faults using job flow patterns and their corresponding fault-recovery policies. Our design has the advantages of separation of the job flow and fault handling logic, requiring no manipulation at the modeling time, and providing flexibility with respect to fault resolution at runtime. We validate our design with a prototypical implementation based on the ActiveBPEL workflow engine and GridWay Meta-scheduler, and Montage application as the case study.

A role-based access control model for information mediation

With the increasing demands for data integration and exchange among distributed heterogeneous sources, many applications require secure interoperation and the information sharing. Mediation techniques provide an extended amalgamation of searching and querying in heterogeneous systems, but enlarge the space of possible threats to local data sources. How to encourage data sharing while enforce required protection to resources is a challenging problem. Traditional access control mechanisms and methods are inadequate to reflect the heterogeneous environment and the flexible access control requirements. This paper presents a mediation security architecture for information integration based on role-based access control (RBAC). An adorned XML model (AXM) is used to homogenize security data modeling. Security requirements of mediation systems are specified by constraints over various RBAC dimensions. An incremental security enforcement method is proposed to integrate RBAC modules into the mediation architecture. The method supports adaptive and scalable design of secure mediation systems.

Monitoring Decentralized Interacting Services with a Global State Choreography Model

This paper presents an approach to the runtime management of decentralized service compositions. The goal of the approach is to transparently observe the behavior of peer-to-peer service interaction in order to permit the introduction of adaptive behavior. The design includes a monitoring component that utilizes a choreography model to formulate a global view of the application, and introduce adaptive behavior in a unique way. The design incorporates a mechanism for transforming the choreography to introduce redundancy, and dynamic selection in the interaction.

Managing Faults for Distributed Workflows over Grids

Grid applications composed of multiple, distributed jobs are common areas for applying Web-scale workflows. Workflows over grid infrastructures are inherently complicated due to the need to both functionally assure the entire process and coordinate the underlying tasks. Often, these applications are long-running, and fault tolerance becomes a significant concern. Transparency is a vital aspect to understanding fault tolerance in these environments.

Runtime Fault-Handling for Job-Flow Management in Grid Environments

The execution of job flow applications is a reality today in academic and industrial domains. In this paper, we propose an approach to adding self-healing behavior to the execution of job flows without the need to modify the job flow engines or redevelop the job flows themselves. We show the feasibility of our non-intrusive approach to self-healing by inserting a generic proxy to an existing two-level job-flow management system, which employs job flow based service orchestration at the upper level, and service choreography at the lower level. The generic proxy is inserted transparently between these two layers so that it can intercept all their interactions. We developed a prototype of our approach in a real Grid environment to show how the proxy facilitates runtime handling for failure recovery.

Data integration in a three-layer mediation framework

Our distributed mediation architecture employs a layered framework of presence, integration, and homogenization mediators. In order to find a mediation path from a client request to data sources, a distributed hash table (DHT) algorithm is deployed in the integration layer. A designated global-mediator in the integration layer initiates the keyword based matching decomposition of the request with the used of the DHT. It generates an integrated data structure graph (IDSG), creates association and dependence relations between nodes in the IDSG, and then it generates a global IDSG (GIDSG). GIDSG is used to stream data from the mediators in the homogenization layer where they connect to the data sources. The architecture is dynamic, scalable and does not have any central point of failure. In this paper we present our research on the use of the GIDSG for the integration of data in our three-layer mediation architecture.