OGSA

Prof S.RamachandramDept of CSE,UCEOsmania University

Major Goals

Identify the use cases that can drive the OGSA platform components

Identify and define the core OGSA platform components

Define hosting and platform-specific bindings

Define resource models and resource profiles with interoperable solutions

More specific goals Facilitating distributed resource management across

heterogeneous platforms Providing seamless QOS delivery Building common base for automatic management solutions Providing common infrastructure blocks to avoid stovepipe

solution towers Open published interfaces and messages Industry-standard integration solutions including web

services Facilities to accomplish seamless integration with existing It

resources where resources become on-demand services/resources

Providing more knowledge-centric and semantic orientation of services

Functional requirements of OGSA

Discovery of resources Instantiating new service Service-level management to meet user expectations Enabling metering and Accounting to quantify resource

usage into pricing units Monitoring resource usage and availability Managing service policies Providing service grouping and aggregation to provide

better indexing and information Managing end-to-end security Servicing life cycle and change management Failure management Provisioning Management Workload management Load balancing to provide a scalable system

Classification of Functions

Basic functions Security functions Resource Management functions System properties

OGSA platform componentsLayers

Native platform services and transport mechanisms

OGSA hosting environment OGSA transport and security OGSA infrastructure( OGSI) OGSA Basic Services (meta-os and

domain services)

Open Grid Service Architecture Three principal elements of OGSA: OGSI,

OGSA services, OGSA applications

OGSA main architecture

OGSA - Definition The Open Grid Services Architecture (OGSA) defines mechanisms for creating, managing,

and exchange information among entities called Grid Services

Grid Service instance: (persistent or transient) service that conforms to a set of conventions (expressed as WSDL interfaces, extensions, and behaviors) for such purposes as lifetime management, discovery of characteristics, notification, and so forth, described from a WSDL PortType

PortType: a WSDL element that describes a collection of message signatures (operation elements) that define the abstract interface of the Web Service

Grid Service instances are made accessible to client applications through the use of a GSH and a GSR

• GSH (Grid Service Handle): URI (uniform resource identifier) that identifies in univocal way a instance, directs to a GSR

• GSR (Grid Service Reference): WSDL document that contains information about the location of the instance

OGSI

OGSI: provides a uniform way for software developers to model and interact with grid services by providing interfaces for discovery, life cycle, state management, creation and destruction, event notification, and reference management

Requesting a service

Important OGSI concepts and interactions

service data, keep-alive,notifications,

service invocation

create service

grid service handleservice requester

servicediscovery

serviceregistry

registerservice

resourceallocation

service factory

serviceinstances

GSH e GSR

URIwww.pc2.it/gsr1

GSH1

WSDL Document

1

GSR1

Grid ServiceInstance

1

URIwww.pc3.it/gsr2

GSH2

WSDL Document

2

GSR2

Grid ServiceInstance

2

Client

Naming

Because Grid services are dynamic and stateful, we need a way to distinguish one dynamically created service instance from another.

Thus, we need a naming scheme for Grid service instances.

Naming

OGSI defines a two-level naming scheme for Grid service instances based on simple, abstract, long-lived Grid service handles (GSH).

GSH can be mapped by handle resolution services to concrete but potentially short-lived Grid service references (GSR).

Naming

A GSH is a globally unique name that distinguishes that specific Grid service instance from all other Grid service instances that have existed, exist now, or will exist in the future.

A GSH is represented using a Uniform Resource Identifier.

Naming

A GSH carries no protocol- or instance-specific information such as network address or supported protocol bindings.

All other instance-specific information is encapsulated into a single abstraction called a Grid service reference (GSR).

Naming

client handleresolver

GSR1 GSR2

serviceinstance

serviceinstance

Resolve (GSH)

time>Ttime<T

migrate

at time T

Grid Service PortTypes (1) A Grid Service can implement following PortType:

GridService: encapsulates the root behavior of the component model

HandleResolver: mapping form a GSH to a GSR

NotificationSource: allows clients to subscribe to notification messages

NotificationSubscription: defines the relationship between a single NotificationSource and NotificationSink pair

NotificationSink: defines a single operation for delivering a notification message to the service instance that implements the operation

Factory: standard operation for creation of Grid Service instances

Registration: allows clients to register and unregister registry contents

Grid Service PortTypes (2)Grid Service

(required)

…other interfaces…

(opzional)

Implementation

Service data access

Explicit destruction

Soft-state lifetime

Standard:

-Notification

-Authorization

-Service creation

-Service registry

-Manageability

-Concurrency

+ application-specific interfaces

Hosting environment/runtime(“C”, J2EE, .NET, …)

WSDL Extensions OGSA architecture introduced WSDL extensions to allow Grid Service

implementation

New WSDL elements:

• serviceData: represents properties of the service’s state that may be externally queried

• serviceDataDescription: formal description of serviceData elements

• Convention on portType name: naming conventions and immutability of portType names

• Grid Service Reference

• Grid Service Handle

ServiceData Concept (1) Service data: to support discovery, introspection, and monitoring of Grid Service

instanceò it refers to descriptive information about Grid Service instance, including

Meta-Data: information about the service instance

State Data: runtime properties of the service instance

Each Grid Service instance has an associated set of SDEs (each one is represented in XML by a serviceData element)

ServiceData Concept (2) serviceData elements samples:

Instance’s data which value can change at runtime

ServiceData Concept (3) Each Grid Service instance is associated with a set of SDEs. This set is modelled

as a serviceDataSet:

serviceData cpuSpeed with relative description: type, value

serviceData configuration with relative description

Grid Service = Interfaces + Service Data

cpuLoad Counter value

Example of Grid Service : DB Service

A DBaccess Grid Service has at least two portType

GridService

DBaccess

Each has any serviceData

GridService: base informations, lifetime informations,…

DBaccess: kind of database, query languages supported, current load,…

Example of Grid Service : DB Service

The UK e-Science Institute collaborate in the OGSA Project, and it implemented a Grid Data Service, a Grid Service with portType to work with many database (relational, XML-DB, …)

http://umbriel.dcs.gla.ac.uk/NeSC/general/

Grid Service

XML-DB portType

Relational-DB portType

…Grid Data Service

GridService portType: operations

FindServiceData: query the service data

RequestTerminationAfter: request that the termination time of this service be changed

RequestTerminationBefore: request that the termination time of the service be changed

Destroy: explicity request destruction of this service

Client

FindServiceData(lifetime)

Factory portType It is used by a client to create an instance of a Grid Service

It is a Grid Service that must implement the Factory portType, which provides a standard WSDL operation for creation of Grid Service instances

The used operation is: CreateService

User Application

Service Provider

Grid Service

Counter Factory

Factory portType It is used by a client to create an instance of a Grid Service

It is a Grid Service that must implement the Factory portType, which provides a standard WSDL operation for creation of Grid Service instances

The used operation is: CreateService

User Application

Service Provider

Grid Service

Counter Factory

CreateService

Factory portType It is used by a client to create an instance of a Grid Service

It is a Grid Service that must implement the Factory portType, which provides a standard WSDL operation for creation of Grid Service instances

The used operation is: CreateService

User Application

Service Provider

Grid Service

Counter Factory

CreateService

Counter

Registration A registry is a Grid Service that maintains a collection of GSH, with policies

associated with that collection. Clients may query the registry to discover what services are available

The registration portType allows clients to register and unregister registry content

The registry makes available a WS-Inspection document (defined with the Web Services Inspection Language – WSIL) to aid in discovery of the services in that registry

Registration

User Application

Service Provider

Grid Service

Registry portType

Registration

User Application

Service Provider

Grid Service

Registry portType

RegisterService(locator 1)

Registration

User Application

Service Provider

Grid Service

Registry portType

RegisterService(locator 1)

GSH 1

Registration

User Application

Service Provider

Grid Service

Registry portType

GSH 1

Registration

User Application

Service Provider

Grid Service

Registry portType

UnregisterService(GSH 1)

GSH 1

Registration

User Application

Service Provider

Grid Service

Registry portType

Transients Database Services

Notification The purpose of the notification is to deliver interesting messages from a

notification source to a notification sink

Notification source: sender of the notification messages

Notification sink: Grid Service instance that receives notification messages from any number of sources

Notification message: XML element sent from a notification source to a notification sink

Subscription expression: XML element that describes what messages should be sent from the notification source to the notification sink

Notification portTypes NotificationSource portType

Subscribe

NotificationSubscription portType: used from Clients to manage the subscription (lifetime and others properties)

NotificationSink portType

deliverNotification

USE CASE OF NOTIFICATION

User Application

Service Provider

Grid Service

Notification portType

X=0

serviceData

USE CASE OF NOTIFICATION

User Application

Service Provider

Grid Service

Notification portType

X=0

serviceData

Subscribe(x=1, sink, exp time)

USE CASE OF NOTIFICATION

User Application

Service Provider

Grid Service

Notification portType

X=0

serviceData

USE CASE OF NOTIFICATION

User Application

Service Provider

Grid Service

Notification portType

X=1

serviceData

USE CASE OF NOTIFICATION

User Application

Service Provider

Grid Service

Notification portType

X=1

serviceData

DeliverNotification(x=1)

HandleResolver portType

A Handle Resolver is a Grid Service instance that implements the HandleResolver portType

FindByHandle: returns a serviceLocator, which contains one or more GSR (Grid Service Reference) for a GSH (Grid Service Handle)