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Research on Integrating service in Grid Portal1

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					            Research on Integrating service in Grid Portal1

                          Zheng Feng, Shoubao Yang, Shanjiu Long,

                                  Dongfeng Chen, Leitao Guo

              Computer Science Dept, University of Science and Technology of China,
                                     230026 Anhui, China
               {fzheng, jlshan, dfchen, ltguo}@mail.ustc.edu.cn
                                   syang@ustc.edu.cn



         Abstract. With the complexity of applications, researchers need more
         resources to resolve their computation. It is very important to provide the
         general interface to access the distributed resources. Grid environment is
         distributed, heterogeneous and dynamics, so integration of different native
         platform is a challenge. We present a service-oriented Grid Portal building on
         concepts and technologies from OGSA. An approach to efficient grid resources
         and customize grid applications is in our framework.




1 Introduction

Portals are commonly used to provide people with access to information and
applications in a condensed form.
Grid Portals are necessary for two reasons. On one hand, the Grid environment is
very complex including scheduling, co-allocation, security, quality of service, data
transfer, network protocol, Grid programming model, etc. On the other hand,
computational science environment is also complex. It’s cumbersome for users to
access a variety of grid resources in single application and follow the changes of
interface, operation system and Grid tools. As a result, users may get overwhelmed in
one single scientific application! Thus, a Grid Portal is defined to be a web based
application server enhanced with the necessary software to communicate with Grid
services and resources.
Most of the existing science portals are application-centric portals, and they actually
share a similarity in some services such as login service, user profile management, etc.
Unfortunately, these common characters have been neglected, which results in the
redundancy in portal implementation. Since developing a professional portal is not an
easy job, why not stop doing repeat jobs and provide a universal service for public
use? What’s more, goal of Grid, by its initiator, is to provide user ubiquitous access to
the Great Global Grid.
Our Portal enables Web Service based universal access to Grid resources.


1   Supported by the National Natural Science Foundation of China under Grant No.60273041
2 Grid Portal

In our Portal design, we pack every Portal function, from Login function to Create
Application Instance function, into a service. Therefore, we can develop a uniform
platform for users and administrator to use these services. This idea facilitates the
complexity of development, as well as the complexity of integrating new services.
The base architecture shows in Fig. 1, so we can get a general idea of our grid portal.




Fig. 1. Architecture of Grid Portal

End user can use web browser or other standalone client to access our grid portal.
When browser sends a HTTP Request to Portal, it will decide which Portlets to
complete the request and diver to them. Portlets use the standard interface to
interactive the Grid Service which described with WSDL. Some standard protocol
such as SOAP, HTTP, and JAVA RPC will be used in communications between
OGSA Client and Grid Service. Portal also provides an interface of Web Service to
standalone client which can use standard SOAP protocol to access the OGSA Client.


3 Integration with Grid service



3.1 Service orientation and virtualization

A Web service is a software system identified by a URI, whose public interfaces and
bindings are defined and described using XML. Its definition can be discovered by
other software systems. These systems may then interact with the Web service in a
manner prescribed by its definition, using XML-based messages conveyed by Internet
protocols.
OGSA defines what we call a 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.
OGSA put heavy emphasis on the concept of “services”: computation resources,
storages resources, networks, programs, databases, and the like are all presented as
services. Everything is service [1].
Virtualization allows the composition of services to form more sophisticated
services—without regard for how the services being composed are implemented.
Virtualization of Grid services also underpins the ability of mapping common service
semantic behavior seamlessly onto native platform facilities.




Fig. 2. Relationships of Portal and Grid Services

In our Grid Portal, we integrated grid service in the portlets [6]. Every portlet service
is compounded by one or more grid service. Portal has a few portlets which can
provide service to users.


3.2 Standard Interface of Grid Service

Dynamic service creation The ability to dynamically create and manage new service
instances is a basic tenet of the OGSA model and necessitates the existence of service
creation services [1]. The OGSA model defines a standard interface (Factory) and
semantics that any service creation service must provide.
Lifetime management Any distributed system must be able to deal with inevitable
failures. In a system that incorporates transient, stateful service instances,
mechanisms must be provided for reclaiming services and state associated with failed
operations.
Notification A collection of dynamic, distributed services must be able to notify each
other asynchronously of interesting changes to their state. OGSA defines common
abstractions and service interfaces for subscription to (NotificationSource) and
delivery of (NotificationSink) such notifications, so that services constructed by the
composition of simpler services can deal with notifications (e.g., for errors) in
standard ways [1]. The NotificationSource interface is integrated with service data, so
that a notification request is expressed as a request for subsequent “push” mode
delivery of service data.


3.3 Class Design

So all classes of grid service inherit from AbstractGridService and implement
ServiceInterface. [4][5] To write a grid service follows 4 steps:
1. Provide a Service Interface
The first step of writing a Grid service is to provide a WSDL definition for the
service interface. We can write service interface definition in WSDL ourselves, or use
tools such as java2wsdl to generate the definition.
2. Generate Service Stubs
The JAX-RPC compliant interfaces are generated to be used both on the client and on
the server side. Client side stub implementations of these interfaces will also be
generated.
3. Implement the Service
All     remotely    available    operations      must     be    public  and     throw
java.rmi.RemoteException as defined in the PortType interface. The ServiceSkeleton
class that must be inherited from is provided by our framework and implements the
GridServicePortType interface, along with other core Grid service behavior [4][7].
4. Deploy the Service


4 Summary

We design and implement a Grid Portal based on concepts and technologies from
OGSA. And with integrating Grid Service in Portal, we provide users a more easy
access to grid resources. Users can also customize their own style of Portal to get
more abundant services.


5 Future work

We will extend role of Grid Portal. It can take the role of auction,balance…That is,
we can extend our Portal to be a Grid resource agency center. There exists some
research on economic marked base Grid resource management. We think Portal will
be particular sense to those economic market based Grid applications.


References

1. I Foster, C Kesselman, J Nick, S Tuecke. Physiology of the Grid: An Open Grid Services
   Architecture for Distributed Systems Integration. January, 2002.
2. I Foster, C Kesselman, S Tuecke. The Anatomy of the Grid: Enabling Scalable Virtual
   Organizations. International J. Super Computer Application, 15(3), 2001.
3. D Gannon, R Ananthakrishnan, S Krishnan, M Govindaraju. Grid Web Services and
   Application Factories.
4. Globus Toolkit. See http://www.globus.org
5. The Global Grid Forum. See http://www.gridforum.org
6. J Novotny, M Russell, O Wehrens. Jetspeed Evaluation. GridLab and Application Portlets
   Design.
7. V Welch, F Siebenlist. GT3 Grid Security Infrastructure Overview.

				
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Description: In the web service based on the services of "grid services" concept, which defines a set of interfaces, these interfaces defined and follow specific practices used to solve the server discovery, dynamic service creation, service lifecycle management, notification and service lifecycle-related issues.