BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 Resource wrappers, web...

BiodiversityWorld GRID WorkshopNeSC, Edinburgh – 30 June and 1 July 2005

Resource wrappers, web services, grid services

Jaspreet Singh School of Computer Science

Cardiff University


Overview

• BDWorld Project• Resource Wrappers• BDWorld Datatypes• BiodiversityWorld-GRID Interface (BGI)

Communications Layer• Web Services based BDW Wrappers• Globus Toolkit 4.0 & WSRF• Grid Services based BDW Wrappers• Further Work


BDWorld Project

• A flexible and extensible problem solving environment (PSE)• Brings together heterogeneous, globally distributed, biodiversity related

resources and analytical tools• The resources can be assembled into set of workflows to perform

complex scientific analysis• Provides consistent mechanisms across various facets to achieve

interoperability• The multi-layered architecture provides data related computation as part

of a separate layer • Provides uniform interfaces for heterogeneous resources• Provides a common resource access mechanism• Standard data flow mechanisms that use well defined data objects• Uses Triana Workflow System for assembling and executing workflows


BDWorld Wrappers

• A mechanism to provide consistent interface to resource users and a standard resource access/invocation mechanism

• Insulate the core BDWorld System from heterogeneous resource• Retains flexibility to use various operations supported by each resource• Provides a generic access mechanism• Wraps various kinds of resources and analytical tools• Can be deployed in Web Services/Grid environment• Provides interoperability mechanisms between client and heterogeneous

resources• Operations on remote resources is invoked via the invokeOperation()

method implemented by all the wrappers• Wrappers give consistent form to data retrieved from heterogeneous

resources by encapsulating them into BDWorld data types


InvokeOperation() method

• The parameters of invokeOperation()method identify:theResourceHandle: name of the resource to be invoked

theOperationHandle: name of the operation to be invoked on the remote resource/tool

theDataCollection is input data collection for the remote resource


Triana Workflow System

Wrapper Logic

Data TransformationConfiguration Tools

Data Transformation Tools

BDW Wrapper

Standard Operations

External Tools

BGI Communications Layer

BDW Wrapper Architecture

Remote Resource

Datatype Tools

Abstract Wrapper


BDWorld Datatypes

• Encapsulate different types of data and sub-datatypes for transporting data between end points

• Datatypes can be transformed into xml representations which can be easily serialised

• Xml schema for datatypes conform to W3C standards• Datatypes are flexible enough to encapsulate user defined

xml documents or data in string representation• They also act as parsing tool to extract data from raw xml• Higher level datatypes can hold several sub datatypes and

each sub datatype can hold several pieces of data• They are extensible and support incorporation of new

datatypes.


BDWorld Datatypes


BDWorld-GRID Interface (BGI) Layer

• Provides standard mechanisms for invoking operations on heterogeneous resources

• provides seamless access to BDW resources via resource wrappers• Uses Xml/SOAP messaging system for invoking operations on resource

wrappers• Act as an integrated mechanism for accessing all resource wrappers• Isolates resources/resource wrapper implementation to enable use of

web services/grid technologies as part of a separate layer• Isolates users from grid/web service complexities• Helper Tool is provided to the user/triana for using the BGI layer• Can provide multiple users/workflows with access to multiple resources at

a time• Interoperable with other e-Science projects


BDW Web Services Architecture

• Web services is a mechanism of enabling distribute computing based on open standards

• Wrappers are currently deployed in a web service environment which can be accessed via the BGI Layer at servers in Cardiff and Reading

• Web services enabled wrappers can be invoked via the BGI Helper Tool

• Axis SOAP engine provides the WSDL that exposes wrapper operations to outside world

• The MetadataAgent WS will provide access to MDR via the BGI Layer


Unit A

Unit B

Unit C

Triana Workflow Units

Data Parsing Tools


BGI Helper Tool

Tomcat Servlet Container/ Axis Soap Engine

MDR

Metadata Agent WS

BDW Web Services Architecture

Remote ResourceExternal Tool

Java /non java resource

WS Interface

BDW Wrapper

WS Interface

BDW Wrapper

WS Interface

BDW Wrapper


Drawbacks of web services

• Web services are not stateful

• WS provide mechanisms for invoking remote operations but does not provide other services such as resource management, persistency, life cycle management, notification etc.

• Each web service needs to be deployed individually


GT4 Key Concepts

• Based on Open Grid Service Architecture (OGSA)• OGSA defines common, standard and open

architecture for grid-based applications• Standardises various services common to grid

applications (job management, resource monitoring and discovery, resource management, security services etc)

• Uses Web Services as underlying technology to enable distributed computing

• But Web Services are not stateful


Web Service Resource and Web Services Resource Framework (WSRF)

• WS-Resource construct expresses relationship between stateful resources and Web Services. It is pairing of web service with a resource

• WSRF is a set of web services specifications which define rendering WS-Resource approach in terms of specific message exchanges and related XML definitions

• It specifies how Web Services can be made stateful• It defines conventions for managing state for applications to discover,

inspect and interact with stateful resources in standard and interoperable way

• Using WSRF associations between a web service and one or more stateful resources can be established

• The state of the WS-Resource can be accessed through a web service interface by using endpoint references

• WSRF is the core of GT4


WSRF Specifications

• WS-ResourceProperties• WS-ResourceLifetime• WS-RenewableReferences• WS-ServiceGroup• WS-BaseFaultsRelated Specifications• WS-Notification• WS-Addressing


Applications

OGSA

Web ServicesWSRF

Stateful Web Services

Web Service

extends

OGSA WSRF

requires specifies

Relation between OGSA, WSRF and GT4 (source: [1])


WSRF – An approach to statefulness

• WSRF provides the mechanism to keep state information by keeping the Web Service and state information completely separate

• State information is stored in entity called resource• A resource is be identified via its unique key• When requiring stateful interaction, a web service

can be instructed to use a particular resource• The resources can be stored in memory or on

secondary storage


Client Web Service

A

B

C

Resources

Interaction of client with a stateful web service (source: [1])

Instruct client to use Resource A

request

response

Web service loads resource A

WS-Resource

Client provides EPR corresponding to Resource A


Grid enabled BDW Resource Wrappers

• Java WS Core component of GT4 being used• Prototype implementation of resource wrappers deployed in

the grid environment• Interaction of Grid enabled wrappers via the BGI Helper Tool• Single integrated mechanism of invoking all resource

wrappers in the grid environment• Grid services invoked via the dynamic loading of resource

wrappers • Resource properties provide access to memory resident

BDW cache data• Access to cache data via EPR from Triana/client without

invoking the resource behind again


Unit A

Unit B

Unit C

Triana Workflow Units

Data Parsing Tools


BGI Grid Helper Tool

BgiWrapperService

BgiWrapper BgiWrapperBgiWrapper

BDWCache BDWCache BDWCacheGT4

Container

MDR

Metadata Agent WS

Remote Resource


Further Work

• Move computation on the grid in addition to resource access mechanism

• BDW Resource pool, automatic update of resources

• Making resources persistent• BDW Heartbeat monitor• Security, Index Service, Monitoring and

Discovery System (MDS), OGSA-DAI for BDW resources


References

[1] Globus Tutorial http://gdp.globus.org/gt4-tutorial/

[2] Global Grid Forum http://www.ggf.org/ggf_abt_overview.htm

[3]The WS-Resource Framework http://www.globus.org/wsrf/specs/ws-wsrf.pdf

http://gdp.globus.org/gt4-tutorial/

http://www.ggf.org/ggf_abt_overview.htm

Date post:	17-Dec-2015
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