Multi-Grid, Multi-User Workflows in the P-GRADE Grid Portal

Computational Grids connect resources and users in a complex way in order to deliver nontrivial qualities of services. According to the current trend various communities build their own Grids and due to the lack of generally accepted standards these Grids are usually not interoperable. As a result, large scale sharing of resources is prevented by the isolation of Grid systems. Similarly, people are isolated, because the collaborative work of Grid users is not supported by current environments. Each user accesses Grids as an individual person without having the possibility of organizing teams that could overcome the difficulties of application development and execution more easily. The paper describes a new workflow-oriented portal concept that solves both problems. It enables the interoperability of various Grids during the execution of workflow applications, and supports users to develop and run their Grid workflows in a collaborative way. The paper also introduces a classification model that can be used to identify workflow-oriented Grid portals based on two general features: Ability to access multiple Grids, and support for collaborative problem solving. Using the approach the different potential portal types are introduced, their unique features are discussed and the portals and Problem Solving Environments (PSE) of our days are classified. The P-GRADE Portal as a Globus-based implementation for the classification model is also presented. The work described in this paper is supported by the Hungarian Grid project (IHM 4671/1/2003), by the Hungarian OTKA project (No. T042459) and a collaboration project with the University of Reading.     

A survey on approaches to gridification

The Grid shows itself as a globally distributed computing environment, in which hardware and software resources are virtualized to transparently provide applications with vast capabilities. Just like the electrical power grid, the Grid aims at offering a powerful yet easy‐to‐use computing infrastructure to which applications can be easily ‘plugged’ and efficiently executed. Unfortunately, it is still very difficult to Grid‐enable applications, since current tools force users to take into account many details when adapting applications to run on the Grid. In this paper, we survey some of the recent efforts in providing tools for easy gridification of applications and propose several taxonomies to identify approaches followed in the materialization of such tools. We conclude this paper by describing common features among the proposed approaches, and by pointing out open issues and future directions in the research and development of gridification methods. Copyright © 2007 John Wiley & Sons, Ltd.     

Grid security: Next steps

One of the more mature instances of a service-oriented architecture is the model known as Grid computing. Computational Grids and Data Grids are becoming commonplace in certain sectors, yet the style of security they implement is suitable only for a fairly small subset of possible user communities. Using some case studies and experience, we describe the existing Grid security models, explain why they represent shortcomings for some applications, and describe some emerging architectures, Trusted Computing and virtualisation, which help address the problems.     

Using a Simple Prioritisation Mechanism to Effectively Interoperate Service and Opportunistic Grids in the EELA-2 e-Infrastructure

Grids currently in production can be broadly classified as either service Grids, composed of dedicated resources, or opportunistic Grids that harvest the computing power of non-dedicated resources when they are idle. While a service Grid provides high and well defined levels of quality of service, an opportunistic Grid provides only a best-effort service. Nevertheless, since opportunistic Grids do not require resources to be fully dedicated to the Grid, they have the potential to assemble a much larger number of resources. Moreover, these Grids cater very well to the execution of the so-called embarrassingly parallel applications, a type of application that is frequently found in practice, and that comprises the largest portion of the typical workload processed in production Grid systems. The EELA-2 e-infrastructure is comprised of a service Grid and an opportunistic Grid that federates computing resources from scientific institutions in both Europe and Latin America. Due to the complementary characteristics of these two types of Grids, a lot of attention has recently been placed in how to interoperate them. In this paper we focus on the less studied problem of assessing the feasibility of such interoperation. We analyse different prioritisation policies that define when the resources of one Grid can be used to run jobs originating from the other. Our results show that in the absence of a suitable prioritisation policy, the benefits that the users of one Grid may have, frequently come with an important negative impact on the users of the other Grid. We also show that a simple reciprocation mechanism is capable of arbitrating the interoperation in such a way that, whenever possible, users profit from the interoperation and, in no case, this benefit leads to a noticeable reduction on the quality of service that the users would experience were the Grids not to interoperate. We conclude discussing how we have implemented, in the context of the EELA-2 project, this prioritisation mechanism, allowing the effective interoperation of a service Grid based on the gLite middleware with an opportunistic Grid that uses the OurGrid middleware.     

JASAG: a gridification tool for agricultural simulation applications

The Grid Computing paradigm aims to create a ‘virtual’ and powerful single computer with many distributed resources to solve resource intensive problems. The term ‘gridification’ involves the process of transforming a conventional application to run in a Grid environment. In that sense, the more automatic this process is, the easier is for developers with low expertise in parallel and distributed computing to take advantage of these resources. To date, many semiautomatic gridifiers were built to support different gridification approaches and application code structures or anatomies. Furthermore, agricultural simulation applications have a particular common anatomy based on biophysical entities, such as animals, crops, and pastures, which are updated by actions, such as growing animals, growing crops, and growing pastures, along simulation execution. However, this anatomy is not fully supported by any of the existing gridifiers. Thus, this paper presents Agricultural Simulation Applications Gridifier (ASAG), a method for easy gridification of agricultural simulation applications, and its Java implementation, named Java ASAG (JASAG). The main design drivers of JASAG are middleware independence, separation of business logic and Grid behavior, and performance increase. An experimental evaluation showing the feasibility of the gridification method and its implementation is also reported, which resulted in speedups of up to 25 by using a real agricultural simulation application. Copyright © 2014 John Wiley & Sons, Ltd.     

一种基于CCM构件模型的计算网格平台

如何聚合网络中分布异构的计算资源来解决大规模的科学计算问题,和如何减少并行程序设计的复杂性,一直是网格计算研究的难点之一。文章提出了一种基于CORBA构件技术的计算网格新思想,构造了一个计算网格的模型(CCGM)。该模型能够充分地利用构件技术带来的可组装和易管理的特性来形成网格计算。并通过问题的抽象定义和使用ParIDL工具将问题的定义映射到CCGM之上,简化了计算网格应用的开发。通过测试和分析CCG(ComponentbasedComputationalGrid)系统,表明CCG系统具有较好的加速比。     

Grid Economics: A Selective Discussion of Two Research Problems

The last 5 years have seen considerable discussion of various types of Grids—compute Grids, storage Grids, and data Grids. Using the checklist given in Foster (, 2002) to define a Grid, two important problems that arise in the context of resource sharing in Grid computing environments are discussed. First, the well documented problem in compute Grid environments that arises from the inability of consumers to accurately estimate their resource requirements is presented. This results in incorrect scheduling of requests for Grid resources and social welfare loss. To address this problem, two research proposals are briefly described. The first approach argues for the design of decision support tools to help users with resource estimation while the second approach studies the design of resource allocation mechanisms that can work with stochastic specifications of resource requirements. This is in contrast to the traditional point estimates of resource required by extant mechanisms. Next, resource provisioning and pricing problems that arise in data storage and retrieval Grids are described. These Grids differ fundamentally from compute Grids but share some economic characteristics with P2P file sharing networks. Drawing on this connection, pricing mechanisms and resource provisioning research is briefly discussed.     

Fault tolerant and prioritized scheduling in OGSA‐based mobile Grids

Grids and mobile Grids can form the basis and the enabling technology for pervasive and utility computing due to their ability to being open, highly heterogeneous and scalable. In this paper we present a scheme for advancing quality of service (QoS) attributes, such as fault tolerance and prioritized scheduling, in OGSA‐based mobile Grids. The fault tolerance is achieved by producing and managing sufficient replicas of tasks submitted for execution on the mobile Grid resources. We design a simple and efficient prioritization scheme, which allows the scheduling of the tasks submitted by the Grid users as distinguished priorities that can be managed and exploited as a QoS parameter by the Grid infrastructure operator. The results that are presented show the efficiency of the proposed scheme in being simple and additionally enriching with reliability and QoS features the applications that are built on the concept of mobile Grids. Copyright © 2008 John Wiley & Sons, Ltd.     

Towards supporting multiple virtual private computing environments on computational Grids

Grid computing now becomes a practical computing paradigm and solution for distributed systems and applications. Currently increasing resources are involved in Grid environments and a large number of applications are running on computational Grids. Unfortunately Grid computing technologies are still far away from reach of inexperienced application users, e.g., computational scientists and engineers. A software layer is required to provide an easy interface of Grids to end users.To meet this requirement HEAVEN (Hosting European Application Virtual ENvironment) upperware is proposed to build on top of Grid middleware. This paper presents HEAVEN philosophy of virtual computing for Grids – a combinational idea of simulation and emulation approaches. The concept of Virtual Private Computing Environment (VPCE) is thereafter proposed and defined. The design and current implementation of HEAVEN upperware are discussed in detail. Use case of Ag2D application justifies the philosophy of HEAVEN virtual computing methodology and the design/implementation of HEAVEN upperware.     

Grid-Controlled Lightpaths for High Performance Grid Applications

Grid applications call for high performance networking support. One attractive solution is to deploy Grids over optical networks. However, resource management in optical domains is traditionally very rigid and cannot successfully meet the requirements of Grid applications, such as flexible provisioning and configuration. In this paper, we present a customizable resource management solution for optical networks where users can create lightpaths on demand and manage their own network resources. Thanks to a Grid-centric system architecture, lightpath resources can be shared among users and easily integrated with data and computation Grids.     

计算网格中资源调度研发现状及展望

网格在解决分散式资源共享方面具有广阔的应用前景,使得它成为下一代互联网瞩目的焦点.而计算网格为资源的需求和供给提供定量分析,激励资源拥有者加入网格的同时保证资源消费者合理有效地使用资源.介绍计算网格通用模型GRACE的基础上,针对该模型中的热点问题--资源管理和调度展开讨论,分析比较当前的几种调度方案,为进一步提出高效完备的资源调度算法作准备.     

A standards-based interoperable single sign-on framework in ARC Grid middleware

Security infrastructure is one of the most challenging tasks in the development, integration and deployment of Grid middlewares. Even though the Grid community addresses the security issue through public key infrastructures (PKI) to support mutual authentication using X.509 certificates, maintaining X.509 credentials is not that easy for non-IT-experts, and has proved to be an obstacle for a more wide deployment of Grid technologies. The identity federation is an increasingly popular technology that can facilitate cross-domain single sign-on without requiring the users to maintain any credentials additional to their own institutional accounts. We believe that utilizing identity federation for Grid middlewares is a promising path for the Grid technology to get more widely used. This paper describes a single sign-on infrastructure developed as a part of the NorduGrid ARC (Advanced Resource Connector) Grid middleware. It adopts the identity federation standard (SAML), as well as other Web Service standards. It focuses on a single sign-on solution at the middleware level for users to access Grids by only using their frequently used accounts, without being bothered to maintain X.509 credentials. Users can use their username/password only to access Grids developed in ARC middleware, as well as access Grids developed in other middlewares that requires users to provide X.509 certificates. Moreover, the single sign-on for workflow-like Grid applications (in which intermediate entities act on behalf of users) is also supported. As an important aspect of single sign-on, authorization is also considered by implementing an attribute-based authorization using SAML standard. In addition, the performance of single sign-on solution is measured. We identify performance limitations of security-related services inside this solution, and analyse the ways to avoid the limitations. To our knowledge, the work presented in this paper is the first evaluated implementation that utilizes identity federation for Grid usage on the middleware level.     

Performance analysis of allocation policies for interGrid resource provisioning

Several Grids have been established and used for varying science applications during the last years. Most of these Grids, however, work in isolation and with different utilisation levels. Previous work has introduced an architecture and a mechanism to enable resource sharing amongst Grids. It has demonstrated that there can be benefits for a Grid to offload requests or provide spare resources to another Grid. In this work, we address the problem of resource provisioning to Grid applications in multiple-Grid environments. The provisioning is carried out based on availability information obtained from queueing-based resource management systems deployed at the provider sites which are the participants of the Grids. We evaluate the performance of different allocation policies. In contrast to existing work on load sharing across Grids, the policies described here take into account the local load of resource providers, imprecise availability information and the compensation of providers for the resources offered to the Grid. In addition, we evaluate these policies along with a mechanism that allows resource sharing amongst Grids. Experimental results obtained through simulation show that the mechanism and policies are effective in redirecting requests thus improving the applications’ average weighted response time.     

GMATE: Dynamic Tuning of Parallel Applications in Grid Environment

Performance is a main issue in parallel application development. Dynamic tuning is a technique that changes certain applications’ parameters on-line to improve their performance adapting the execution to actual conditions. To perform that, it is necessary to collect measurements, analyze application behavior and carry out tuning actions during the application execution. Computational Grids present proclivity for dynamic changes in the environment during the application execution. Therefore, dynamic tuning tools are necessary to reach the expected performance indexes of applications on those environments. This paper addresses the dynamic tuning of parallel/distributed applications on Computational Grids. We analyze Grid environments to determine their characteristics and we present the development of dynamic tuning tool GMATE enabled for such environments. The performance analysis is based on performance models that indicate how to improve the application execution. A particular problem which provokes performance bottlenecks is the load imbalance in Master/Worker applications. A heuristic to dynamically tune granularity of work and number of workers is proposed. Finally, we describe the experimental validation of the performance model and its applicability on a set of real parallel applications.     

Reputation-based dependable scheduling of workflow applications in Peer-to-Peer Grids

Grids facilitate creation of wide-area collaborative environment for sharing computing or storage resources and various applications. Inter-connecting distributed Grid sites through peer-to-peer routing and information dissemination structure (also known as Peer-to-Peer Grids) is essential to avoid the problems of scheduling efficiency bottleneck and single point of failure in the centralized or hierarchical scheduling approaches. On the other hand, uncertainty and unreliability are facts in distributed infrastructures such as Peer-to-Peer Grids, which are triggered by multiple factors including scale, dynamism, failures, and incomplete global knowledge.In this paper, a reputation-based Grid workflow scheduling technique is proposed to counter the effect of inherent unreliability and temporal characteristics of computing resources in large scale, decentralized Peer-to-Peer Grid environments. The proposed approach builds upon structured peer-to-peer indexing and networking techniques to create a scalable wide-area overlay of Grid sites for supporting dependable scheduling of applications. The scheduling algorithm considers reliability of a Grid resource as a statistical property, which is globally computed in the decentralized Grid overlay based on dynamic feedbacks or reputation scores assigned by individual service consumers mediated via Grid resource brokers. The proposed algorithm dynamically adapts to changing resource conditions and offers significant performance gains as compared to traditional approaches in the event of unsuccessful job execution or resource failure. The results evaluated through an extensive trace driven simulation show that our scheduling technique can reduce the makespan up to 50% and successfully isolate the failure-prone resources from the system.     

Achieving efficiency, quality of service and robustness in multi-organizational Grids

Scalability, flexibility, quality of service provisioning, efficiency and robustness are the desired characteristics of most computing systems. Although the emerging Grid computing paradigm is scalable and flexible, achieving both efficiency and quality of service provisioning in Grids is a challenging task but is necessary for the wide adoption of Grids. Grid middleware should also be robust to uncertainties such as those in user-estimated runtimes of Grid applications. In this paper, we present a complete middleware framework for Grids that achieves user satisfaction by providing QoS guarantees for Grid applications, cost effectiveness by efficiently utilizing resources and robustness by intelligently handling uncertain runtimes of applications.     

Characterizing Grids: Attributes, Definitions, and Formalisms

Grid systems and technologies have evolved over nearly a decade; yet, there is still no widely accepted definition for Grids. In particular, the essential attributes that distinguish Grids from other distributed computing environments have not been articulated. Most approaches to definition adopt a static view and consider only the properties and components of, or the applications supported by, Grids. The definition proposed in this paper is based on the runtime semantics of distributed systems. Rather than attempt to simply compare static characteristics of Grids and other distributed computing environments, this paper analyzes operational differences, from the viewpoint of an application executing in both environments. Our definition is expressed formally as an Abstract State Machine that facilitates the analysis of existing Grid systems or the design of new ones with rigor and precision. This new, semantical approach proposes an alternative to the currently accepted models for determining whether or not a distributed system is a Grid.     

Dynamic Instrumentation, Performance Monitoring and Analysis of Grid Scientific Workflows

While existing work concentrates on developing QoS models of business workflows and Web services, few tools have been developed to support the monitoring and performance analysis of scientific workflows in Grids. This paper describes novel Grid services for dynamic instrumentation of Grid-based applications, performance monitoring and analysis of Grid scientific workflows. We describe a Grid dynamic instrumentation service that provides a widely accessible interface for other services and users to conduct the dynamic instrumentation of Grid applications during the runtime. We introduce a Grid performance analysis service for Grid scientific workflows. The analysis service utilizes various types of data including workflow graphs, monitoring data of resources, execution status of activities, and performance measurements obtained from the dynamic instrumentation of invoked applications, and provides a rich set of functionalities and features to support the online monitoring and performance analysis of scientific workflows. Workflows and their relevant information including performance metrics are stored and utilized for comparing the performance of constructs of different workflows and for supporting multi-workflow analysis. The work described in this paper is supported in part by the Austrian Science Fund as part of the Aurora Project under contract SFBF1104 and by the European Union through the IST-2002-511385 project K-WfGrid.     

Grid programming: some indications where we are headed

Grid computing enables the development of large scientific applications on an unprecedented scale. Grid-aware applications, also called meta-applications or multi-disciplinary applications, make use of coupled computational resources that are not available at a single site. In this light, the Grids let scientists solve larger or new problems by pooling together resources that could not be coupled easily before. It is well known that the programmer’s productivity in designing and implementing efficient distributed/parallel applications on high-performance computers is still usually a very time-consuming task. Grid computing makes the situation worse. Consequently, the development of Grid programming environments that would enable programmers to efficiently exploit this technology is an important and hot research issue.

After an introduction on the main Grid programming issues, this paper will review the most important approaches/projects conducted in this field worldwide.