steve graham [email protected]

Steve Graham [email protected]

WS-ResourceFrameworkTechnical Overview

OASIS Tutorial Sunday, April 26th, 2004

© 2004 IBM Corporation 2

Agenda

Introduction, Motivation and Core concepts

Overview of the WS-ResourceFramework specifications

• Resource Properties• Resource Lifetime• ServiceGroup• BaseFaults

Demo

WS-Notification discussion

Conclusions


Motivation

Stateful entities exist in most systems

• Data in a purchase order• Current usage agreement for resources • Metrics associated with work load on a server

Hitherto: no standard way to deal with state in Web services context

• Each system does it in “idiosyncratic way”• Integration impediment

Goal:

• Formalize a mechanism to represent “state” in Web services• In order to help unify Grid computing, Systems management

and e-business computing


Scope of WS-ResourceFramework

How to represent state in a Web services context

How is state referenced and “identified” in Web services

How is state modeled in XML and WSDL

How is state accessed through Web services

How to reason about lifetime of state

How to aggregate/collect stateful resources

How to reason about fault messages


Overview of Scenario

At several points we will use examples from the systems management domain

In particular, imagine applications that use Web services to view/manipulate operating systems and processes that run on them

processProcessPropertiescreationClassNamecreationDatecsCreationClassNamecsNameexecutionStatehandlekernelModeTimenameosCreationClassNameosNamepriorityterminationDateworkingSetSizeCurrentTimeTerminationTime

GetResourceProperty()QueryResourceProperties()Destroy()

OperatingSystemOSPropertiescreationClassNamecsCreationClassNamecsNamefreePhysical MemoryfreeVirtualMemorynamenumberOfProcessesnumberOfUsersoperationalStatusosTypetotalSwapSpaceSizetotalVirtualMemorytotalVisibleMemoryversionCurrentTimeTerminationTime

findAllOperatingSystems()findHostedPorcesses()GetResourceProperty()QueryResourceProperties()Destroy()


What is a Web Service ?

An operation execution component made available at an endpoint address

• A service is defined in terms of the operations it implements

– An operation is defined in terms of a message exchange

• The supported set of messages exchanges (operations) implemented by a service may be described as a WSDL portType

• The Web service itself is typically stateless Accessible through use of a WS-Addressing Endpoint

Reference

Lifecycle of a Web service typically described in terms of “deployment”


What do we mean by Stateful Resource ?

A specific set of state data expressible as an XML document;

Has a well-defined identity and lifecycle; and Known to, and acted upon, by one or more Web

services. Many possible implementations

• Files, Database tables, EJB Entities, XML documents, Composed from multiple data sources, etc.

Lifecycle expressed in terms of resource creation and destruction• Multiple independent instances may be created and destroyed• Identity is assigned at creation time


WS-Addressing: Referencing Web services Standardizes the representation of the address of a Web service

deployed at a given network endpoint A WS-Addressing endpoint reference is an XML serialization of a

network-wide pointer to a Web service EPRs can be used to pass services to other services by reference Dynamic generation and customization of service endpoint descriptions Identification and description of specific service instances that are

created as the result of stateful interactions An EPR contains:

• Service address (wsa:Address)• Metadata associated with the Web service such as service description

information (WSDL)• Policy information related to the use of the service• Reference properties, which can be used to identify specific stateful

resource instances associated with the Web service at the endpoint address (wsa: ReferenceProperties)


Inte

rface

WebService

message

message

address

Endpoint Reference

Run-time environment

Invoking a Web service using WS-Addressing


WS-Resource

WS-Resource: Web service + associated resource• In other words:

– A resource with an associated Web service A WS-Resource has:

• Identity: Can be uniquely identified/referenced• Lifetime: Often created & destroyed by clients• State: Can be projected as an XML document • Type: Its Web service interface

An EPR “points to” a WS-Resource• WS-Resource Qualified Endpoint Reference• Implied Resource Pattern


Contents of EndpointReference

Service

Requestor

A

B

C

1

5

4

2

<wsa:EndpointReference> <wsa:Address> http://someOrg.com/process </wsa:Address> <wsa:ReferenceProperties> <tns:process> C </tns:process> </wsa:ReferenceProperties> </wsa:EndpointReference> 3


context

Inte

rface

WebService

messageid

message

id

address

resource


Endpoint Reference

Using an EPR to Access a WS-Resource


context

Inte

rface

WebService

messageid

message

id

address

resource

resource

Endpoint ReferenceEndpoint Reference

Different WS-Resources, Different EPRs



The WS-Resource Qualified Endpoint Reference

Service

Requestor

<soap:Envelope> <soap:Header> <tns:process> C </tns:process> </soap:Header> <soap:Body> … some message </soap:Body> </soap:Envelope> … </soap:Envelope>

A

B

C

3

2

1 C

4

An endpoint reference containing a WS-Resource identifier is a WS-Resource-qualified endpoint reference.


WS-Resource Identifier

The WS-Resource identifier is a “lookup key” the WS-Resource to be used in the execution of the request message

• The set of reference properties

The content of the WS-Resource identifier is opaque to the service requestor

• The service requestor’s applications should not examine or attempt to interpret the contents of the WS-Resource identifier

• The WS-Resource identifier is meaningful only to the Web service

From the point of view of the service requestor:

• EPR is a pointer to the Web service + WS-Resource • In other words, the EPR represents a pointer to a WS-Resource

accessible through a Web service


Inte

rface

WebService

message

message

address

Endpoint Reference

resource

Endpoint Reference

address

id

Creating/Locating a WS-Resource



WS-Resource Relationship Cardinality

A Web service can execute message exchanges against zero or more WS-Resources of a given type

One Stateful resource can be “associated” with multiple Web services

• Different interfaces, or same interface for redundancy At the type level, a WSDL 1.1 portType, defining the interface to a Web

service, can be associated with at most one “kind” or “type” of WS-Resource

One “kind” or “type” of WS-Resource can be associated with many WSDL 1.1 portTypes

A

CWS1

B

WS2


WS-Resource Composability

WS-RF is part of the Web services set of technologies

Key to Web services is the notion of composability• Web services is a (growing) set of small(ish) specs• Systems are built by “composing” these specs in

various ways• Eg

– WS-RF DOES NOT define a security model» Use WS-Security

– WS-RF DOES NOT define a reliable messaging model» Use WS-ReliableMessaging

– WS-RF DOES NOT define a transactions model» Use WS-AtomicTransaction, etc.

– ETC.


Agenda




Demo


Conclusions


WS-ResourceFramework

A family of documents and specifications• CA, Fujitsu, Globus, HP, IBM

White papers:• Modeling Stateful Resources with Web services

– “State Paper”

• WS-Resource Framework overview• OGSI -> WS-RF

Specifications• WS-ResourceProperties• WS-ResourceLifetime• WS-ServiceGroup• WS-BaseFaults

WS-

Serv

ice

Gro

ups

WS-

Not

ifica

tion

Modeling Stateful

Resources with Web Services

WS-B

ase Faults

WS-ResourceProperties W

S-Resource

Lifetime


Status of WS-ResourceFramework

Specifications announced on January 20, 2004• WS-ResourceProperties, WS-ResourceLifetime, State Paper• http://www-106.ibm.com/developerworks/webservices/library/ws-resource/

Co-author feedback session on February 16

Public feedback session February 23

Specifications updated March 5

• Added the WS-RF overview paper and OGSI->WSRF paper OASIS Technical Committee call for participation March 9

WS-BaseFaults and WS-ServiceGroup on March 31

• Public feedback April 16 Interoperability “fest” April 20

First meeting of OASIS TC April 28


Agenda




Demo


Conclusions


Defines:• How to use XML schema to model elements of

resource state • How to associate resource’s state model with

WSDL portType• Standard operations for getting, setting, querying, • Standard mechanism to use WS-Notification to

subscribe for state value changes

Why:• Basis for standard resource inspection, monitoring

and state management

WS-ResourceProperties


How is State Modeled?

XML of course

• Instance document associated with a WS-Resource• The WS-Resource’s “Resource Properties document”

Elements of state are modeled as child elements of the root <process:ProcessProperties>

<process:csName> xclock </process:csName> <process:executionState> Suspended Ready </ …> <process:handle> 2824 </process:handle>… <wsrl:CurrentTime> 23 Apr 2004 19:45:29 GMT </ … > <wsrl:TerminationTime xsi:nil=“true” /></process:ProcessProperties>

XSD:ref is used to “combine” Resource Properties from various definitions

<xsd:element name="ProcessProperties" type="process:ProcessPropertiesType"/>

<xsd:complexType name="ProcessPropertiesType">

<xsd:sequence>

<xsd:element ref="process:Name"/>

<xsd:element ref="process:CSName"/>

<xsd:element ref="process:OSName"/>

<xsd:element ref="process:Handle"/>

<xsd:element ref="process:Priority"/>

<xsd:element ref="process:ExecutionState"/>

<xsd:element ref="process:CreationDate"/>

<xsd:element ref="process:TerminationDate"/>

<xsd:element ref="process:KernelModeTime"/>

<xsd:element ref="process:WorkingSetSize"/>

<xsd:element maxOccurs="1" minOccurs="1" ref="process:resourceID"/>

<xsd:element maxOccurs="1" minOccurs="1" ref="wsrl:CurrentTime"/>

<xsd:element maxOccurs="1" minOccurs="1" ref="wsrl:TerminationTime"/>

…


ResourceProperties Document and WSDL

ResourceProperties document is associated with the wsdl portType:

<wsdl:portType name="Process"

wsrp:ResourceProperties="process:ProcessProperties">

<wsdl:operation name="findHostingOperatingSystem"> …

<wsdl:operation name="GetResourceProperty"> …

<wsdl:operation name="QueryResourceProperties"> …

<wsdl:operation name="Destroy"> …

</wsdl:portType>

@ResourceProperties provides meta-data to assist developers and value-add tooling


WS-ResourceProperties Operations

GetResourceProperty

• Simple single resource property element getter• Required• <wsrp:GetResourceProperty> process:handle</wsrp:GetResourceProperty>

• <wsrp:GetResourcePropertyResponse> <process:handle>1577 </process:handle></wsrp:GetResourceProperty>

<wsrp:GetResourceProperty> QName </wsrp:GetResourceProperty>



Get Multiple Resource Properties

• More sophisticated multiple property value retrieval• Optional • <wsrp:GetMultipleResourceProperties> <wsrp:ResourceProperty>process:handle </ …> <wsrp:ResourceProperty>process:executionState <wsrp:ResourceProperty>process:csName </…></wsrp:GetMultipleResourceProperties>

• <wsrp:GetMultipleResourcePropertiesResponse> <process:handle>2824 </process:handle> <process:executionState>Suspended Ready </… <process:csName> xclock </process:csName></wsrp:GetMultipleResourcePropertiesResponse>

<wsrp:GetMultipleResourceProperties> <wsrp:ResourceProperty>QName </wsrp:ResourceProperty>* </wsrp:GetMultipleResourceProperties>



QueryResourceProperties

• Execute an expression against the resource properties document

• Optional• QueryExpression defines dialect by URI

– XPath 1.0, 2.0– XQuery– SQL– StevesAmazingQueryExpression

<wsrp:QueryResourceProperties> <wsrp:QueryExpression dialect=”URI”> xsd:any </wsrp:QueryExpression> </wsrp:QueryResourceProperties>



Set Resource Properties

• Modify a resource property document• optional

<wsrp:SetResourceProperties> { <wsrp:Insert > xsd:any* </wsrp:Insert> |

<wsrp:Update > xsd:any * </wsrp:Update> |

<wsrp:Delete ResourceProperty=”QName” /> }+ </wsrp:SetResourceProperties>


Agenda




Demo


Conclusions


WS-ResourceLifetime Defines:

• Immediate, synchronous destruction operation• Time-based, scheduled destruction operation

– “Soft-state” or “leased” lifetime management– Termination time no required to monotonically increase

• Resource properties:– CurrentTime: Can be used to determine clock skew– TerminationTime: Current scheduled termination time

• Notification of resource termination Why:

• Define clear means by which WS-Resources can be destroyed


WS-ResourceLifetime

Immediate Destruction

Scheduled Destruction

Resource Properties

• Current Time• Termination Time

<wsrl:Destroy />

<wsrl:SetTermination> <wsrl:RequestedTerminationTime> xsd:dateTime </wsrl:RequestedTerminationTime> </wsrl:SetTerminationTime>


Agenda




Demo


Conclusions


WS-ServiceGroup Defines:

• Web service interfaces for representing and managing a by-reference collection of EPRs to Web services or WS-Resources

• Each entry is member EPR + associated content– WS-RP used for representing the entries– Can have rules to membership and content– Members may be homogenous or heterogenous, depending on the

purpose and membership rules of the group• Has a registration interface for adding entries

– Follows the WS-Resource factory pattern– The entry is represented as a WS-Resource

• WS-RL used for removing entries Why:

• Myriad of reasons for groups: E.g. Registries, collective operations, federated services, etc.


ServiceGroup Model


ServiceGroup Interfaces ServiceGroup

• A collection of Web services and the information that pertains to them.

• Purpose is application domain specific ServiceGroupEntry

• A Web service that represents the member and associated content

ServiceGroupRegistration

• Message exchange for adding new members to a ServiceGroup• Membership may occur in other ways

Member

• (any Web service)


ServiceGroup Characteristics When a ServiceGroup is destroyed, all of the

ServiceGroupEntries are also recommended to be destroyed. However, the members are not affected.

Once a ServiceGroup is destroyed, no assumptions can be made about either the existence of the ServiceGroupEntry or it’s contents.

A member may belong to several ServiceGroups.

A member may belong to the same ServiceGroup more then once.

The member of a ServiceGroup may implement message exchanges from various interfaces.

If a member is destroyed, the ServiceGroup may destroy the corresponding ServiceGroupEntry(s).


ServiceGroup Resource Properties MembershipContentRule

• These elements specify the constraints on membership of the service group

Entry

• These elements represent the projection of the aggregation of the resource property documents of the ServiceGroup’s entry resources


Agenda




Demo


Conclusions


WS-BaseFaults Defines

• Set of “common” properties of a fault• Convention for specializing “common” fault• How “common” fault type is used in WSDL

Why?

• Increases the likelihood that service requestors to automatically (without human intervention) understand and/or adapt to faults requires interface designers to define rich, structured fault messages

• Standard fault messages encourage tooling that can assist interface designers, service implementers, and client implementers


BaseFault Element<BaseFault> <-- type=BaseFaultType -->

<Timestamp>xsd:dateTime</Timestamp>

<OriginatorReference>

wsa:EndpointReferenceType

</OriginatorReference> ?

<ErrorCode dialect="anyURI">xsd:string</ErrorCode> ?

<Description>xsd:string</Description> *

<FaultCause>wsbf:BaseFault</FaultCause> *

</BaseFault>


BaseFaultType Information Items Timestamp (required)

• Time at which the fault occurred OriginatorReference (optional)

• WS-Addressing EndpointReference of the WS that generated the fault

• Can omit if it is clearly implied• Useful particularly with FaultCause

ErrorCode (optional)• String error code for supporting legacy fault reporting systems• @dialect: URI specifying context of string

Description (0..unbounded)• Plain language description(s) of the fault• Use with xsi:lang

FaultCause (0..unbounded)• BaseFault element(s) that describes the underlying cause of

this fault.


Using BaseFaultType For each distinct fault on WSDL operation

1. Define XSD complexType that extends BaseFaultType• Represents the fault’s distinct type• May not define any additional fields

2. Define XSD element with this extended fault type3. Define WSDL message using this fault element4. Define WSDL operation fault element using this

messag


Binding to SOAP

WS-BaseFaults only specifies what is done at WSDL 1.1 abstract interface (portType) level

• Intended for defining service/application faults Binding a fault message to SOAP is the purview of

a WSDL binding definition

• Use standard WSDL 1.1 SOAP 1.1 binding Issue: Some redundancy between WS-BaseFault

information and SOAP 1.2 faults

• May want some changes to WS-BaseFaults for WSDL 2.0 and its SOAP 1.2 binding


Agenda




Demo


Conclusions


The Demo Services and Scenarios

Ability to find known operating systems represented as services. Ability to find all processes hosted on a given operating system

represented as services. Monitor and introspect both operating system and process state via

resources properties. Destroy (terminate) a selected process resource via its services

interface.

Operating System

Service

Process

Service

Pegasus CIMOMHa

nd

lers

Process

OS

WebSphere


Demo Details

Pegasus CIMOM

ProcessOS

Ha

nd

lers

Operating System

Service

Process

Service

WebSphere

Client

Proxies

EPRHelpers

Ha

nd

lersClient

UI

Client Container

Web Services

Servlets

Stateless

Session

Beans

EJB Container

EPRHelpers

Ha

nd

lers

Web Container

Entity

Beans


Demo

WSAD IE 5.1 on Windows XP• Integration Test Server 5.1

– WBI Runtime

Pegasus 2.3.1 on RH 9.0

• sblim base providers


Agenda




Demo


Conclusions


WS-Notification WS-Notification

• Brings enterprise quality publish and subscribe messaging to Web services

– Loosely coupled, asynchronous messaging in a Web services context

• WS Notification exploits WS Resource framework and other Web services technologies

• Direct and Brokered notification• Topics and Topic Spaces• More on subscribe• Use of WS-Notification in WS-RF


WS-Notification Family of Documents

WS-Notification is a family of documents:• Publish-Subscribe for Web services

– Whitepaper describing roles, concepts, terms, etc.

• Base Notification– Basic interfaces: Producer, Consumer, Subscription

• Topics– Topics and TopicSpaces model in XML– Topic Expression Dialects

• Brokered Notification– Mechanisms of Publish and the Broker role

Authored by:• CA, Fujitsu, Globus, HP, IBM

+ Akamai, SAP, Sonic, Tibco


Status of WS-Notification

Specification announced on January 20, 2004• http://www-106.ibm.com/developerworks/webservices/library/ws-notification/

Co-author feedback session on February 17

Public feedback session February 24

Specifications updated March 5

• Factored into 4 documents (see previous slide) OASIS Technical Committee call for participation

March 9

Interoperability “fest” April 21

First meeting of OASIS TC April 29


Consumer

Producer

Subscriber

WS-Notification: Base Notification

subscribe

subscribe

S

notify

EPR

Defines the Basis for the familyDirect notification: Three primary rolesSubscriber deals directly with the

producer of the Notifications• indicates interest in a particular

“Topic” by issuing a “subscribe” request

An EPR to the subscription is returned

Producer is responsible fordetecting situation and creating the notification

Subscriptions that matchreceive the notification


Similar roles as in direct, adding ‘Broker’ Role

• Broker (intermediary) permits decoupling Publisher and Subscriber

Subscriber indicates interest in a particular “Topic” by issuing a “subscribe” request

“Subscriptions” are WS-Resources

• Various subscriptions are possible New role: Publisher

• need NOT be a Web Service Publisher detects situation:

• Publishes the Notification to a broker

Broker responsible for disseminating notifications

• examines current subscriptions for match Brokers may provide “value add”

• “Transform” or “interpret” topics• Federate to provide scalability

Broker

Subscriber

WS-Notification: Brokered Notification

Publisher

subscribe

subscribe

S S S

notify

notify

notify

notify


WS-Notification

More on Subscribe Request

Returns EPR to a Subscription WS-Resource

<wsnt:Subscribe> <wsnt:ConsumerReference>EPR </wsnt: ConsumerReference> <wsnt:TopicExpression dialect=“URI”/> <wsnt:UseNotify> xsd:boolean </wsnt:UseNotify>? <wsnt:Precondition> wsrp:QueryExpression </Precondition>? <wsnt:Selector> wsrp:QueryExpression </wsnt:Selector>? <wsnt:SubscriptionPolicy> any </wsnt:SubscriptionPolicy>? <wsnt:InitialTerminationTime> xsd:dateTime </wsnt:InitialTerminationTime>?</wsnt: Subscribe>


WS-Notification

Topics and Topic Spaces

• Meta-data to help– Organize Notifications– Tell the Subscriber what to subscribe to<?xml version="1.0" encoding="UTF-8"?>

<wstop:topicSpace name="TopicSpaceExample1" targetNamespace="http://example.org/topicSpace/example1" … > <wstop:topic name="t1"> <wstop:topic name="t2" messageTypes=“tns:m1 tns:m2"/> <wstop:topic name="t3" messageTypes=“tns:m3"/> </wstop:topic> <wstop:topic name="t4"> <wstop:topic name="t5" messageTypes=“tns:m3"/> <wstop:topic name="t6" aliasRef="tns:t1/t3"/> </wstop:topic></wstop:topicSpace>



Subscription for Value Change Rules for mapping resource properties to Topics

• QName of resource property corresponds QName of Topic To subscribe to changes in process:ExecutionState:

Suggested format of value change message

<wsnt:Subscribe> <wsnt:ConsumerReference>… <wsnt:TopicExpression dialect=“uri”> process:executionState <wsnt:TopicExpression> …</wsnt: Subscribe>


Shameless Plug for My (upcoming) Book


Credits

Most of the material is the result of collaborative effort from:• Steve Graham, Jeff Frey, Jay Unger, Steve Tuecke

and Tom Maguire. BaseFaults section derived from material courtesy

of Steve Tuecke ServiceGroup section derived from material

courtesy of Tom Maguire Demo and scenario derived from material courtesy

of:• Mike Williams, Revathi Subramanian, JaiPaul

Antony, Bob Hansen

steve graham [email protected]

Documents

web serviceshow

web servicesstandardizes

web serviceeprs

web services contexthow

wsdl porttypethe web

endpoint addressa service

web servicesin order

service address wsa