전산학과 20025230 이재승jasonlee@etri.re.kr

The Physiology of the GRID

2003. 06. 10

I. Foster, C. Kesselman, J. Nick, and S. TueckeOpen Grid Service Infrastructure WG, Global Grid Forum, June 22, 2002 

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Table of Contents

1. Introduction 2. The Need for Grid Technologies3. Background4. An Open Grid Services Architecture5. Application Example6. The OGSA Service Model7. Network Protocol Bindings8. Higher-Level Services9. Related Work10. Conclusion11. Discussion

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1. Introduction

Problem

In e-business and e-science, we need to integrate services across distributed, heterogeneous, dynamic “virtual organizations” formed from the disparate resources within a single enterprise and/or from external resource sharing and service provider relationships.

This integration can be technically challenging because of the need to achieve various QoS when running on top of different native platforms.

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1. Introduction

Solution: Open Grid Services Architecture

defines a uniform exposed service semantics (the Grid service)

defines standard mechanisms for creating, naming, and discovering transient Grid service instances

provides location transparency and multiple protocol bindings for service instances

supports integration with underlying native platform facilities

defines mechanisms for creating and composing distributed systems including lifetime management, change management, and notification

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1. Introduction Focus

on the services that respond to protocol messages

how Grid technologies can be aligned with Web services technologies

(We call this alignment an Open Grid Services Architecture (OGSA)) - WSDL interfaces for a Grid service - service instance supporting reliable and secure invocation - lifetime management, notification, policy management, credential management, and virtualization - discovery of Grid service instances and creation of transient Grid service instances.

on commercial applications rather than the scientific and technical applications

Requirements:

- seamless integration with existing resources and applications

- tools for workload, resource, security, network QoS, and availability management.

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2. The Need for Grid Technologies The Evolution of Enterprise Computing

Rise of the Internet and e-business intelligent network IT services decomposition is also occurring inside enterprise IT facilities.

- different programming models, commodity servers

- need to distribute and cache content closer to the edge of the network

Need for highly robust IT infrastructure

IT systems integrators take on the burden of re-integrating distributed compute resources with respect to overall QoS.

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2. The Need for Grid Technologies

Service Providers, B2B Computing

emergence of SPs demands:

- dynamic resource allocation in accordance with service-level agreement policies

- consistent response times and high levels of availability

B2B Collaboration demands: - security, auditability, availability, service level agreements, and complex transaction processing flows

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3. Background

The Globus Toolkit

community-based, open-architecture, open-source set of services and software libraries that support Grids and Grid applications.

security, information discovery, resource management, data management, communication, fault detection, and portability

GRAM protocol, gatekeeper service: secure, reliable, service creation and management

MDS-2: information discovery, data modeling, local registry

GSI: single sign on, delegation, and credential mapping.

essential elements of a service-oriented architecture

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3. Background

The Globus Toolkit (cont)

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3. Background Web Services

focus on simple,Internet-based standards to address heterogeneous distributed computing

SOAP: provides a means of messaging between a service provider and a service requestor

WSDL: Service interfaces are defined abstractly in terms of message structures and sequences of simple message exchanges

WS-Inspection: comprises a simple XML language and related conventions for locating service descriptions published by a service provider.

Web Services - advantages

dynamic discovery and composition of services in heterogeneous environments

Web services can exploit numerous tools and extant services

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4. An Open Grid Services Architecture Service Orientation and Virtualization

OGSA focus on services:

computational resources, storage resources, networks, programs, databases, and

the like are all represented as services

critical requirement is interoperability

service-oriented view allows us to address the need for standard interface definition mechanisms, local/remote transparency, adaptation to local OS services, and uniform service semantics

Virtualization allows for consistent resource access across multiple heterogeneous platforms with local or remote location transparency

OGSA supports local and remote transparency with respect to service location and invocation.

OGSA provides for multiple protocol bindings

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4. An Open Grid Services Architecture Service Semantics: The Grid Service

a Web service that provides a set of well-defined interfaces and that follows specific conventions

The interfaces address discovery, dynamic service creation, lifetime management, notification, and manageability

The conventions address naming and upgradeability

The interfaces and conventions are concerned with behaviors related to the management of transient service instances

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4. An Open Grid Services Architecture The Grid Service – Upgradeability Conventions and Transport Protocol

Services within a complex distributed system must be independently upgradeable

- versioning, compatibility must be managed

A service’s description indicates the protocol bindings that can be used to communicate with the service.

- Reliable Service Invocation

- Authentication

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4. An Open Grid Services Architecture The Grid Service – Standard Interfaces

Discovery

Dynamic Service Creation

Lifetime management

Destroy

Notification

Other Interfaces: authorization, policy management, concurrency control ….

(in the near future)

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4. An Open Grid Services Architecture

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4. An Open Grid Services Architecture

The Role of Hosting Environments OGSA answers the `what-question', not the `how-question'

OGSA does not address issues of implementation programming model, programming language, implementation tools, or execution environment.

OGSA specifies interactions between services in a manner independent of any hosting environment

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4. An Open Grid Services Architecture

Using OGSA Mechanisms to Build VO StructuresSimple Hosting Environment Virtual Hosting Environment Collective Operations

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5. Application Example

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6. The OGSA Service Model Creating Transient Services: Factories

Factory interface creates new Grid service instances.

The Factory interface’s CreateService operation creates a requested Grid service and returns the GSH and initial GSR for the new service instance.

Service Lifetime Management

Soft state approach: Grid service instances are created with a specified lifetime.

advantages:

- A client knows, or can determine, when a Grid service instance will terminate - A hosting environment is guaranteed that resource consumption is bounded, even in the face of system failures outside of its control.

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6. The OGSA Service Model Managing Handles and References

The result of a factory request: a GSH and a GSR

GSH (Grid Service Handle): is guaranteed to reference the created Grid service instance in perpetuity

GSR (Grid Service Reference): is created with a finite lifetime and may change during the service’s lifetime.

(WSDL document describes how to communicate with the Grid Service)

how does one establish communication with a Grid service given only its GSH?

define a handle-to-reference mapper interface (Handle Map)

Each Grid service instance should be registered with at least on handleMap, called home handleMap, which is included in the GSH

Identification of the home handleMap is established by requiring that all home handleMap services be identified by a URL

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6. The OGSA Service Model Service Data and Service Discovery

A set of service data is associated with each Grid service instance.

GridService interface defines a standard WSDL operation, FindServiceData, for querying and retrieving service data.

One application of the GridService interface’s FindServiceData operation is service discovery

Registry interface is used to register a GSH and the GridService interface’s FindServiceData operation is used to retrieve information about registered GSHs.

Notification

OGSA notification framework allows clients to register interest in being notified of particular messages (the NotificationSource interface)

OGSA supports asynchronous, one-way delivery of such notifications (NotificationSink).

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6. The OGSA Service Model Change Management

Any changes made to the definition of a Grid service must be reflected through new interface names

This feature allows clients that require Grid Services with particular properties to discover compatible services.

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7. Network Protocol Bindings Four Primary Requirements

Reliable transport: support for reliable service invocation ex) HTTP-R

Authentication and delegation: support for communication of proxy credentials to remote sites ex) TLS extended with proxy credential support

Ubiquity: It must be possible for any arbitrary pair of services to interact

GSR Format: ex) WSDL document

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8. Higher-Level Services Distributed data management services

Workflow services

Auditing Services

Instrumentation and monitoring services

Problem determination services for distributed computing

Security protocol mapping services

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some current Globus Toolkit protocols

a potential refactoring to exploit OGSA mechanisms

8. Higher-Level Services

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9. Related Work

Globus Toolkit v2.0

factory (GRAM gatekeeper), registry (GRAM reporter, MDS-2), secure remote invocation with delegation (GSI), reliable remote invocation (GRAM) is form Globus Toolkit v2.0

differences: how these difference mechanisms are integrated

no uniform interface definition language

Distributed Object System

OGSA exploits ideas developed previously in systems such as Eden, Argus,CORBA, SOS, Spring, Globe, Mentat, and Legion

In contrast to CORBA, OGSA like Web services addresses directly issues of secure interoperability and provides a richer interface definition language

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9. Related Work Applications of Web services mechanisms to Grid

De Roure et al. propose a “Semantic Grid,” by analogy to the Semantic Web, and propose a range of higher-level services

Work on service-oriented interfaces to numerical software in NetSolve and Ninf

Etc

Sun Microsystems’ JXTA system addresses several important issues encountered in Grids, including discovery of, and membership in, virtual organizationsgroups.”

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10. Conclusion

OGSA supports the creation, termination, management, and invocation of stateful, transient services as named, managed entities with dynamic, managed lifetime.

Within OGSA, everything is represented as a Grid service, that is, a service that conforms to a set of conventions (expressed using WSDL) for such purposes as lifetime management, discovery of characteristics, notification, and so on.

The merits of the service-oriented model:- All components of the environment are virtualized

By providing a core set of consistent interfaces, we facilitate the construction of services that can be treated in a uniform way - Virtualization also enables mapping of multiple logical resource instances onto the same physical resource, composition of services regardless of implementation

By integrating support for transient, stateful service instances with existing Web services technologies, OGSA extends significantly the power of the Web services framework, while requiring only minor extensions to existing technologies.

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11. Discussion Performance, end-to-end QoS

Development Environment, Hosting Environment, Implementation Issues

Deployment Issues

commercial service 에 바로 적용 가능한가 ?

과연 dominant 한 computing 환경으로 자리 잡을 수 있을까 ?