Sergio Andreozzi

GridICE: a monitoring service for Grid systems

Grid systems follow a new paradigm of distributed computing that enables the coordination of resources and services that are not subject to centralized control, can dynamically join and leave virtual pools, and are assigned to users by means of an explicit assignment functionality. The monitoring of a Grid is a multi-institutional and Virtual Organization (VO)-oriented service. It must deal with the dynamics, diversity, and geographical distribution of the resources available to Virtual Organizations, and the various levels of abstraction for modeling them. This paper presents the requirements, architecture and implementation of GridICE, a monitoring service for Grid systems. The suitability of this tool in real-life scenarios is analyzed and discussed.

The gLite workload management system

The gLite Workload Management System (WMS) is a collection of components that provide the service responsible for distributing and managing tasks across computing and storage resources available on a Grid. The WMS basically receives requests of job execution from a client, finds the required appropriate resources, then dispatches and follows the jobs until completion, handling failure whenever possible. Other than single batch-like jobs, compound job types handled by the WMS are Directed Acyclic Graphs (a set of jobs where the input/output/execution of one of more jobs may depend on one or more other jobs), Parametric Jobs (multiple jobs with one parametrized description), and Collections (multiple jobs with a common description). Jobs are described via a flexible, high-level Job Definition Language (JDL). New functionality was recently added to the system (use of Service Discovery for obtaining new service endpoints to be contacted, automatic sandbox files archival/compression and sharing, support for bulk-submission and bulk-matchmaking). Intensive testing and troubleshooting allowed to dramatically increase both job submission rate and service stability. Future developments of the gLite WMS will be focused on reducing external software dependency, improving portability, robustness and usability.

Towards a model for quality of Web and grid services

The service oriented model is the emerging approach adopted by Web and grid services where parties act as service requestors and service providers. An aspect to consider is improving machine-to-machine interaction by enabling an automatic evaluation and selection of available services with respect to a set of expectations. This paper presents a model for the rigorous representation of service characteristics, for the association of each of their possible values with the requester satisfaction, and for the aggregation of the single satisfactions in an overall score using a particular logic. The proposed model is exemplified in the area of grid computing.

Towards a Metamodeling Based Method for Representing and Selecting Grid Services

The service oriented model is the emerging approach adopted by Web and Grid services where parties act as service requestors and service providers. A meaningful aspect to consider consists in improving machine-to-machine interaction by enabling an automatic evaluation and selection of available services with respect to a set of expectations. In this context, it can be useful to raise the modeling abstraction level by considering the metamodeling theory principles by which to enhance the modeling constructs. The goal of this paper is to present a method for the rigorous representation and selection of service characteristics in the area of Grid computing. Such a method relies on the measurement theory and the Logic Scoring of Preferences (LSP). Moreover, relying on the metamodeling theory provided by the OMG Model Driven Architecture (MDA), a prototype tool for mapping MOF based Grid services metamodels in domain specific textual languages is presented.

Standards-Based Job Management in Grid Systems

The Grid paradigm for accessing heterogeneous distributed resources proved to be extremely effective, as many organizations are relying on Grid middlewares for their computational needs. Many different middlewares exist, the result being a proliferation of self-contained, non interoperable “Grid islands”. This means that different Grids, based on different middlewares, cannot share resources, e.g. jobs submitted on one Grid cannot be forwarded for execution on another one. To address this problem, standard interfaces are being proposed for some of the important functionalities provided by most Grids, namely job submission and management, authorization and authentication, resource modeling, and others. In this paper we review some recent standards which address interoperability for three types of services: the BES/JSDL specifications for job submission and management, the SAML notation for authorization and authentication, and the GLUE specification for resource modeling. We describe how standards-enhanced Grid components can be used to create interoperable building blocks for a Grid architecture. Furthermore, we describe how existing components from the gLite middleware have been re-engineered to support BES/JSDL, GLUE and SAML. From this experience we draw some conclusions on the strengths and weaknesses of these specifications, and how they can be improved.

Recent evolutions of GridICE: a monitoring tool for grid systems

Grid systems must provide its users with precise and reliableinformation about the status and usage of available resources. The efficient distribution of this information enables Virtual Organizations (VOs) to optimize the utilization strategies of theirresources and to complete the planned computations. In this paper, we describe the recent evolution of GridICE, a monitoring tool for Grid systems. Such evolutions are targeted at satisfying the requirements from the main categories of users: Grid operators, site administrators, Virtual Organization (VO) managers and Grid users.

Monitoring the connectivity of a grid

Grid computing is a new paradigm that enables the distributed coordination of resources and services which are geographically dispersed, span multiple trust domains and are heterogeneous. Network infrastructure monitoring, while vital for activities such as service selection, exhibits inherent scalability problems: in principle, in a Grid composed of <i>n</i> resources, we need to keep record of <i>n</i>² end-to-end paths. We introduce an approach to network monitoring that takes into account scalability: a Grid is partitioned into domains, and network monitoring is limited to the measurement of domain-to-domain connectivity. However, partitions must be consistent with network performance, since we expect that an observed network performance between domains is representative of the performance between the Grid Services included into domains.

XMatch: A language for satisfaction-based selection of Grid services

Grid systems enable the sharing of a large number of geographically-dispersed resources among different communities of users. They require a mapping functionality for the association of users requests expressed in terms of requirements and preferences to actual resources. This functionality should deal with a potentially high number of similar resources and with the diversity of the perceived satisfactions of users. We propose XMatch, a query language enabling the expression of the user request in terms of the expected satisfaction over XML-based representation of available resources. This language offers a compact way for users to express their preferences for Grid resources and enable the maximization of the global preference.

Answering the Cost Assessment Scaling Challenge: Modelling the Annual Cost of European Computing Services for Research

ICT costs have been traditionally assessed using well-established methods such as full cost accounting or total cost of ownership. Within their specific, optimal application areas they provide very good tools for cost follow-up and strategic decision-making. However, as the scale and complexity of the system being analysed grows, these methods become less suitable. In particular, due to the complex funding structures, and the multi-supplier and cross-country nature of service provision, estimating the total costs of European computing services for research is perhaps one of the best examples of such complex, large-scale systems. Solving this challenge is crucial for the sustainability of these services: besides obvious technical budgeting challenges, difficulties in comparing the cost-effectiveness of different service delivery options make sustaining public support for funding more arduous than it should be. This paper presents a novel cost assessment methodology that addresses the above challenges and uses an in-depth analysis of the pan-European computing e-Infrastructure costs as a case study illustrating the use of the methodology. We also use this case study as an illustration of the kind of cost assessment issues that high-utilisation rate computing services should consider when choosing between different infrastructure options (for example comparing costs per core hour of in-house resources and public Cloud offerings).

Implementation and Performance Analysis of XMatch: a Language for Quality-based Selection of Grid Services

Grid systems focus on the sharing and coordination of a large number of geographically- dispersed resources among different communities of users. Such systems require the capability of associating users requests to the actual resources. This capability should consider a high number of similar resources and different perceptions of users satisfaction concerning the selected resources. In order to face this problem, in our previous work we have proposed XMatch, a query language enabling the expression of the user request in terms of the expected satisfaction over XML-based representations of available resources. In this paper, we present an XMatch implementation consisting in rewriting XMatch queries in terms of XQuery expressions. We also propose a performance analysis based on real-world use cases. This implementation and evaluation of XMatch shows the suitability of the language for the identified use cases and the feasibility of its application.