Service Grids

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Service Grids
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Presentation Outline

• What is web service?
• What is grid?
• What is service grid?
• OGSA (Open Service Grid Arch.)

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Web Services

• A possible definition
• A Web service is a software system identified by
  a URI, whose public interfaces are defined and
  described using XML. Other systems may interact
  with the Web service in a manner prescribed by
  its definition, using XML based messages conveyed
  by internet protocols.
• It is NOT
• A web page
• A web server
• A Java Server Page
• Related to Web browsers or portals
• It is an agent, a software system, a component.

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Web Services

• Follows the SOA concepts
• Emphasis on interoperability
• XML, XML, XML
• Platform Independent
• Three specifications were seen as the foundation
• SOAP (Simple Object Access Protocol)
• WSDL (Web Services Description Language)
• UDDI (Universal Description, Discovery and
  Integration)

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Web Services
.NET Application
MS IIS and ASP.NET
Legacy Application
J2EE Application
Soap Messages
Soap Server
Soap Server
Internet
Soap Messages
Soap Messages
Soap Messages
Soap Stack
Client Application
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Web Services Arch.
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What is Grid?

• Grid is everything you would like it to be.
• Virtual organizations
• Integration of distributed resources
• Universal computer
• Interconnection technologies for supercomputers
• Coordinated resource sharing and problem solving
  in dynamic, multi-institutional virtual
  organisation

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What is Grid?

• Interoperability
• protocol focus on the externals rather than
  internals
• Service-oriented
• A service is defined by the protocol that it
  speaks and behaviour it implements

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What is Service Grid?

• In the beginning there was Globus for the Grid.
• Then web services came along and everybody talked
  about them.
• Globus team has decided to create the Service
  Grid.
• Service Grid provides some functionalities to
  application services running, such as message
  queuing, routing, security...

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Why Service Grid?

• When technologists have finished describing the
  core standardsprotocols underlying Web Services
  technology, they move quickly to application
  level.
• That is, all attention is focused on
  standardsprotocols and application services
• Without Service Grids the potential of Web
  Services can not be fully realized
• Lots of problems appear when web services and P2P
  are integrated.

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Why Service Grid?

• For example, in P2P area
• Connections are not robust.
• Security is ???.
• No indication of resource orchestration.

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The Importance of Managed Services

• A distributed services architecture will be
  required before web service technology can be
  broadly deployed to support mission critical
  applications
• Service Grids provide a set of enabling utilities
  and services to support more robust connections
  in distributed environments.

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The Importance of ManagedServices

• Distinct from application functionality that is
  directly useful to end-users
• The focus is on supporting these applications
  with security, routing of messages, data
  transformations...
• Service grids are like middleware that provides
  managed services, rather than installed in the
  computers at either end.

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The Importance of Managed Services

• Standarts alone can not provide these
  functionalities.
• With WSDL, the provider can describe its WS
• Who will verify that the information is correct?
• Who will audit the performance?
• Who will offer the billing capability?
• Who will collect the payments?
• Who will manage the directory services?

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Web Services Architecture
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Utilities within Service Grids

• Shared Utilities provide services that support
  not only the application services but also the
  other utilities.
• Security
• Performance, auditing, assesment
• Billing and payment

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Utilities within Service Grids

• Transport management utilities
• Messaging services - facilitates reliable and
  flexible communication among application
  services.
• Resource orchestration assemble sets of
  application services from different providers
• Routing

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Utilities within Service Grids

• Resource knowledge management utilities
• Directories
• Registries - describes avaliable services and
  determines the correct way of interacting them
• Data transformation - conversion of data from one
  format to another

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Utilities within Service Grids

• Service Management Utilities
• Quality of Service conformance to QoS specs.
• Monitoring monitoring performance

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Service Grids Federation of Utilities

• A distributed architecture of optional network
  overlays.
• Provider and users of web services can choose to
  use the avaliable functionality.
• Service grids are likely to be federated with
  each other to increase capacity.

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Advantages

• Reducing the complexity at the edges
• Useful especially for small companies which can
  not afford to develop such services
• Mediate among competing standards and policies
  (If we have to wait the standards to mature and
  converge, adoption of WS would be delayed)
• Helping to develop shared meaning
• amortize development cost (use from other
  companies)
• Automation of some administrative activities.

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OGSA

• The main concern is on the creation, management,
  and application of dynamic ensembles of resources
  and services.
• These are called Virtual Organizations (VO).
• allows for consistent resource access across
  multiple heterogeneous platforms with local or
  remote location transparency.
• allows the composition of services to form more
  sophisticated services.
• enables management of resources within a VO based
  on composition from lower-level resources.
• Local and remote transparency with respect to
  service location and invocation.

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OGSA

• Web services address discovery invocation of
  persistent services
• Interface to persistent state of entire
  enterprise
• In Grids, must also support transient service
  instances, created/destroyed dynamically
• To do this, so something better than WS is
  needed
• GRID SERVICE

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Grid Service

• A Web service that provides a set of well-defined
  interfaces and that follows specific conventions.
• The interfaces are factory, mapper, lifetime
  management, discovery, registry, authorization,
  notification.

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Grid Service

• Factory requested to create a new Grid service
  instance.
• Mapper allows a client to map from a GSH to a
  GSR.
• Lifetime Man. GS instances created by factory or
  manually destroyed explicitly or via soft state.
• Discovery allows clients to query the Grid
  service instance for this information

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Grid Service

• Registry interface may be used to discover a set
  of Grid service instances.
• Authorization handles authentication during
  invocation of Grid service operation.
• Notification distributed services can notify
  each other asynchronously of interesting changes
  to their state.

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Grid Service

• Some interfaces (in WSDL terms, portTypes)

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Constructing Grid Environments
In each case, Registry handle is effectively the
unique name for the virtual organization.
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Factory

• A Grid service with Factory interface can be
  requested to create a new Grid service instance
• Reliable creation (once-and-only-once)
• Returns a Grid Service Handle (GSH)
• A globally unique URL
• Uniquely identifies the instance for all time
• Based on name of a home mapper service

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Mapper

• A GSH is a stable name for a Grid service, but
  does not allow client to actually communicate
  with the Grid service
• A Grid Service Reference (GSR) is a WSDL document
  that describes how to communicate with the Grid
  service
• Contains protocol binding, network address,
• May expire (I.e. GSR information may change)
• The Mapper interface allows a client to map from
  a GSH to a GSR

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Thank You