http://www.epcc.ed.ac.uk/~ogsanet

ogsanet-queries@epcc.ed.ac.uk

February 24th-25th 2004

Web Services and Grid Services

Mike Jackson – EPCC

Some slides in this presentation are graciously provided by the OGSA-DAI Project

2

Purpose

XML and Web Services Grids OGSA OGSI

3

XML and Web Services

4

Web Services (1/2)

Network-enabled application Exposes a well-defined interface Often Stateless:

– Born– Services Request– Dies

State maintenance dependant on service hosting environment Accessible using common Internet protocols:

– HTTP

XML-oriented technology:– Describe services and their interfaces:

• WSDL – Web Services Description Language

– Support messaging:• SOAP – Simple Object Access Protocol

5

WSDL

Web Services (2/2)

Client

Web ServiceApplication

Code

Application Code Database

SOAP Request

SOAP Response

6

XML

eXtensible Markup Language Standard format for structured documents and data:

– Supports exchange over heterogeneous platforms

Human-readable:– Less efficient than proprietary formats

Address the limitations of HTML:– Application-specific syntax and semantics

7

An Example of XML

<?xml version="1.0" encoding="ISO-8859-1"?>

<!-- A list of attendees on some course -->

<attendees>

<attendee id=“123”>

<name first-name=“Mike” last-name=“Jackson”/>

<institution>EPCC</institution>

</attendee>

<attendee id=“456”>

<name first-name=“Daragh” last-name=“Byrne”/>

<institution>EPCC</institution>

</attendee>

</attendees>

8

XML Namespaces (1/3)

<film-types>

<film-type>RomCom</film-type>

<film-type>Spaghetti Western</film-type>

</film-types>

<film-types>

<film-type>amphipathic</film-type>

<film-type>hydrophobic</film-type>

</film-types>

9

XML Namespaces (2/3)

Telephone numbers:– Within Edinburgh University: 50-5141

– Within Edinburgh: 650-5141

– Within the UK: 0131-650-5141

XML namespaces:

<xmlns:bio=“http://bio.stuff/membrane” bio:film-types>

– Namespace prefix:• Declaration: xmlns:• Maps to URI reference: bio

– URI reference:• Global URI: “http://bio.stuff/membrane”

– Local part: film-types– Qualified name: bio:film-types

10

XML Namespaces (3/3)

<xmlns:cinema=“http://world.cinema/flix” cinema:film-types>

<cinema:film-type>RomCom</cinema:film-type>

<cinema:film-type>Spaghetti Western</cinema:film-type>

</cinema:film-types>

<xmlns:bio=“http://bio.stuff/membrane” bio:film-types>

<bio:film-type>amphipathic</bio:film-type>

<bio:film-type>hydrophobic</bio:film-type>

</bio:film-types>

11

XML Schema

Specify the structure of XML documents:– Names of elements and attributes

– Content of elements

– Values of attributes

– Namespaces of elements

XML Schema are XML documents Facilitates validation of XML documents:

– Check conformance of document to XML Schema:• Are elements nested legally?• Do elements have legal attributes?• Do attributes have legal values?

More information from:– http://www.w3.org/XML/Schema

12

SOAP (1/2)

Simple Object Access Protocol:– a stateless,– one-way,– message exchange paradigm

Framework to convey application-specific information in an extensible manner

Specifies rules for:– SOAP envelopes – container for:

• Header: originator and destination and application-specific information e.g. payment or authentication details about the SOAP message

• Body: message data

– Data encoding format– Conventions for message encoding:

• Document-style• RPC-style

13

SOAP Example (1/2)

<soapenv:Envelope>

<soapenv:Header>

<wsse:Security

soapenv:actor=“http://some.security.intermediary"

soapenv:mustUnderstand=“1">

. . .

</wsse:Security>

</soapenv:Header>

<soapenv:Body>

<!–- An RPC call to a sayHelloWorld() operation -->

<sayHelloWorld/>

</soapenv:Body>

</soapenv:Envelope>

14

SOAP Example (2/2)

<soapenv:Envelope> <soapenv:Header> <wsse:Security soapenv:actor=“http://some.security.intermediary" soapenv:mustUnderstand=“1"> . . . </wsse:Security> </soapenv:Header> <soapenv:Body> <sayHelloWorldResponse> <!–- The result of the sayHelloWorld() operation --> <helloMessage>Hello World!</helloMessage>

</sayHelloWorldResponse> </soapenv:Body></soapenv:Envelope>

15

SOAP (2/2)

Silent on: – Semantics of any application-specific data it conveys– Routing of SOAP messages– Reliable data transfer

– Firewall traversal Can operate over various transports:

– HTTP– FTP– SMTP

Fully describes the required actions to be taken by a SOAP node on receiving a SOAP message

More information from– http://www.w3.org/2000/xp/Group/

16

WSDL (1/2)

Web Services Description Language – 1.1 XML description of Web Services:

– Define input and output messages– Define operations in terms of input and output messages– Aggregate operations into portTypes:

• Application-specific collections of related operations.

– Combine portTypes with a concrete network protocol and message format to form a binding:

• How to communicate to a service’s portType.

– Combine a binding and a network address to define a concrete network endpoint or port:

• Where to find a service’s portType.

– Aggregate ports into an abstract network endpoint or service

17

WSDL (2/2)

WSDL is extensible:– Allows description of endpoints and their messages – Regardless of what message formats or network protocols are used to

communicate

Typically used in conjunction with following protocols and message formats:– SOAP 1.1– HTTP GET/POST– MIME

More information from:– http://www.w3.org/TR/wsdl

18

WSDL Example (1/3)<?xml version="1.0" encoding="UTF-8"?><definitions name="HelloWorld"> <types> <xsd:schema> <!-- For example <helloMessage>HelloWorld!</helloMessage> --> <xsd:complexType name="HelloMessageType"> <xsd:sequence> <xsd:element name="helloMessage“ type="xsd:string"/> </xsd:sequence> </xsd:complexType> <!-- For example <sayHelloWorld/> --> <xsd:element name="sayHelloWorld"> <xsd:complexType/> </xsd:element> <!-- For example <sayHelloWorldResponse> <helloMessage>HelloWorld!</helloMessage> </sayHelloWorldResponse/> --> <xsd:element name="sayHelloWorldResponse" type="HelloMessageType"/> </xsd:schema>

</types>

19

WSDL Example (2/3)

<message name="HelloInputMessage"> <part name="parameters“ element="sayHelloWorld"/> </message> <message name="HelloOutputMessage"> <part name="parameters" element="sayHelloWorldResponse"/> </message> <portType name="HelloWorldPortType"> <operation name="sayHelloWorld"> <input message="HelloInputMessage"/> <output message="HelloOutputMessage"/> </operation> </portType>

20

WSDL Example (3/3)

<binding name="HelloWorldSOAPBinding" type="helloworld:HelloWorldPortType"> <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/> <operation name="sayHelloWorld"> <soap:operation

soapAction="http://www.tutorial.org/myservices/helloworld#sayHelloWorld"/>

<input><soap:body namespace="http://www.tutorial.org/myservices/helloworld" use="literal"/></input> <output><soap:body namespace="http://www.tutorial.org/myservices/helloworld" use="literal"/></output> </operation> </binding></definitions>

21

Web Services – Summary

XML:– eXtensible Markup Language– Namespaces– XML Schema

SOAP:– Simple Object Access Protocol– Stateless, one-way message exchange paradigm

WSDL:– Web Services Description Language– Abstract interface description– Concrete service location and communication information.

Web Services:– Stateless– XML-oriented technology

22

Grids

23

Motivating Grids

Difficult problems – “Grand Challenges” – require:– Collaboration– Sharing:

• Ideas

• Efforts

• Resources – computational, data, storage

Emerging Open Grid Infrastructures will:– Support global collaboration– Change the way that we work

24

What are Grids?

Grids are about dynamic Virtual Organisations (VOs) sharing data and computing resources

Virtual Organisations:

“Dynamic groups of individuals, institutions, and resources, which have a well-defined set of sharing and Quality-of-Service (QoS) rules associated with

them”P. Z. Kunszt, The Open Grid Services Architecture: A Summary and Evaluation, CERN, April 2002.

25

Virtual Organisations

VOs include:– Resource users– Resource providers:

• Including application, data and storage service providers

Resources include:– Data resources– Servers– Other programs

Resource Usage Policies:– Grid end-users can utilise resources according to:

• The policies (rules) of the VO of which they are a member of• The policies of the resource providers

Dynamic VOs:– VOs should be able to change in scope and extension, transparently from the

end users, or clients

26

Examples of VOs

Scientific Collaborations:– e.g. Astronomers, Geneticists, Physicists, Medics:

• Need to share and integrate data

• Need to share computing power for data analysis

Engineering Collaborations:– e.g. Aircraft design and construction consortia:

• Need to share computing power for simulations for design

• Need to share and integrate analysis data and results

Business:– e.g. Business-to-Business (B-to-B):

• Need to share and integrate data

• Need to share computing power for e.g. data mining, market simulations

27

Open Grids

Open Grids enable:

– Coordinated and coherent collaboration

– Resource sharing

Service component-based Grids enable heterogeneous environments to be integrated and reconciled to accomplish complex tasks

Service components support heterogeneity:

– Interface- and message-passing-based

– Hide platform and implementation

28

OGSA

29

What is OGSA?

Open Grid Services Architecture:

– Open Grid Architecture + Web Services = Grid Services

Grid Services:– Dynamic– Transient– Stateful – have a finite lifetime– Defined by a well-defined set of interfaces and behaviours

More information from:– http://forge.gridforge.org

30

OGSA Characteristics

Supports:– Resource access

– Resources sharing

– Service integration

– Uniform access to services

Specifies protocols and standards that:– Are:

• Implementation-independent• Platform-independent

– Support:• Communication• Data access, transfer, translation and transformation• Access and security• Auditing and logging

31

Best of Both Worlds

Web Services

Business integration

Secure and universal access

Applications on demand

Grid Protocols

Vast resourcescalability

Global Accessibility

Resourceson demand

ContinuousAvailability

Accessresource

Manageresource

Shareresource

Open Grid Services Architecture

32

OGSA Structure

System Management Services

Web Services

Open Grid Services Infrastructure

Grid Services

33

OGSI

34

What is OGSI?

Open Grid Services Infrastructure Minimum set of standards and behaviours with which Grid Services must

comply Exploits existing Web Services properties:

– Interface abstraction via WSDL portTypes– Web Service protocols– Hosting platform-independent

Extends these to provide for:– State management– Event notification– Service location and access– Lifecycle management– Service data

More information from:– http://forge.gridforge.org

35

OGSI PortTypes (1/2)

GridService:– findServiceData– setServiceData– requestTerminationBefore– requestTerminationAfter– destroy

Factory:– createService

HandleResolver:– findByHandle

ServiceGroup ServiceGroupRegistration:

– add– remove

36

OGSI PortTypes (2/2)

ServiceGroupEntry NotificationSource:

– subscribe

NotificationSubscription NotificationSink:

– deliverNotification

37

Grid Service Identification

Grid Services are identified by means of a– Grid Service Handle (GSH), which is used to find the– Grid Service Reference (GSR) that is unique to an instance of a Grid

Service.– A HandleResolver service is used to provide a GSR given a GSH

GSH:– Type of URI (or URL)– Constant for the lifetime of the Grid Service.

GSR:– Representation of the service interfaces:

• Can be a WSDL document

– Can change if the service evolves

38

Anatomy of a Grid Service (1/4)

Hosting Environment

•Service Data Access•Lifetime Management

•Service Creation•Service Grouping•Notification•Handle Resolution

•Other functions e.g:•Workflow•Auditing•Resource Management

HandleHandle

Grid Service

GridService portType(required)

Other PortTypes(Optional)

39

Anatomy of a Grid Service (2/4)

Hosting Environment

•Service Data Access•Lifetime Management

GridService portType(required)

Other PortTypes(Optional)

•Service Creation•Service Grouping•Notification•Handle Resolution

•Other functions e.g:•Workflow•Auditing•Resource Management

HandleHandle

ServiceDataSet

40

Anatomy of a Grid Service (3/4)

Hosting Environment

•Service Data Access•Lifetime Management

GridService portType(required)

Other PortTypes(Optional)

•Service Creation•Service Grouping•Notification•Handle Resolution

•Other functions e.g:•Workflow•Auditing•Resource Management

HandleHandle

Service

Data

Service

Data

Service

Data

41

Anatomy of a Grid Service (4/4)

Grid Service

PortType PortTypePortType PortType

SDESDE

SDEServiceData

SDESDE

SDEServiceData

SDESDE

SDEService Data

SDESDE

SDEServiceData

PortTypeImpl.cs PortTypeImpl.cs PortTypeImpl.cs PortTypeImpl.cs

42

WSDL and GWSDL

WSDL 1.1:– Lack of portType inheritance:

• A portType cannot be defined in terms of an aggregation or extension of one or more other portTypes

– Lack of an open content model:• Needed for specifying service data

GWSDL:– portType inheritance– Open content model

GWSDL => WSDL 1.1:– Flattening the inheritance hierarchy– The “most-derived” portType

WSDL 2.0:– Currently a draft standard– Replace GWSDL

43

GWSDL and Flattening

GridService

setServiceData() findServiceData()

requestTerminationBefore() requestTerminationAfter()

destroy()

ServiceGroup

ServiceGroupRegistration

add() remove()

MyService

setServiceData() findServiceData()

requestTerminationBefore() requestTerminationAfter()

destroy()

add()

remove()

myOperation()

MyService

myOperation()

44

OGSI Implementations

Microsoft .NET:– EPCC: MS.NETGridOGSI Release 1.2– University of Virginia: OGSI.NET Release 2.1

Java:– Globus: Globus Toolkit 3 Release 1.0– Unicore

Perl:– University of Manchester: OGSI::Lite

Python:– Lawrence Berkley National Labs: pyGlobus

45

WSRF

Web Services Resource Framework Access and manipulate state via Web Services:

– WS-Resource – a stateful resource

Replaces OGSI:– WS-Addressing for resource identification– WS Resource Framework rendered in terms of six new specifications:

• WS-ResourceProperties• WS-ResourceLifetime• WS-Notification• WS-RenewableReferences• WS-ServiceGroup• WS-BaseFault

More information from:– http://www.globus.org/wsrf – Especially: “From Open Grid Services Infrastructure to WS-Resource

Framework: Refactoring”

46

OGSI => WSRF

GWSDL => WSDL1.1

+ portType flattening pending WSDL 2.0 GSH => WS-Addressing Endpoint Reference

+ WS-RenewableReferences GSR => WS-Addressing Endpoint Reference Service data => Resource properties GridService portType => WS-ResourceProperties

+ WS-ResourceLifetime Factory portType => Factory pattern ServiceGroup portTypes => WS-ServiceGroups Notification portTypes => WS-Notification HandleResolver portType => WS-RenewableReferences Operation Faults => WS-BaseFault

47

Grid Services – Summary

Grids:– Virtual Organisations

– Sharing, access and management of distributed, heterogeneous resources

Open Grid Services Architecture:– Grid Services = Web Services + Open Grid Architecture

– State + lifetime

Open Grid Services Infrastructure:– Building blocks of OGSA service

– Service lifetime management, state access, registration, notification, creation, access

– Service identification – GSH + GSR

– Service description – GWSDL

Web Services Resource Framework