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OGSA Notification and RGMA

OGSA Notification and RGMA. Datagrid meeting 13/5/2003 <a.djaoui@rl.ac.uk>. Notification in the Grid. Allows asynchronous communication between a client and a server Either direct or through intermediary services (messaging, filtering, archival, …) More resilient to faults (no hang-ups)

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OGSA Notification and RGMA

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  1. OGSA Notification and RGMA Datagrid meeting 13/5/2003 <a.djaoui@rl.ac.uk>

  2. Notification in the Grid • Allows asynchronous communication between a client and a server • Either direct or through intermediary services (messaging, filtering, archival, …) • More resilient to faults (no hang-ups) • Better scalability WP3

  3. Use of Notification in RGMA • Registry: • Producers notify relevant Consumers • Streaming: • No need for permanent connection from Consumer to Producer • Producer sends notification message to all subscribed Consumers • Need reliable Notification Framework implementation • Other: Consumer/producers, Replication, … WP3

  4. OGSI basics • PortType = interface • Every Grid service implements The GridService portType • similar to Object class in Java • lifecycle management • introspection • Service Data • part of service instance state • exposed to service requestors for query, update and change notification (like java beans properties) • Grid Service Handle GSH • a permanent network pointer to a particular Grid service instance • Should be resolved to a GSR in order to acccess instance WP3

  5. OGSI Notification Pattern • NotificationSource portType: • Allows clients to subscribe to Notification messages. • Notification can be associated with any (authorised) SDE. • NotificationSink portType : • Defines a single operation for delivering a notification message to the service instance that implements the operation • Notification Subscription portType: • Defines the relationship between a single NotificationSource and NotificationSink pair. WP3

  6. NotificationSource portType • Service Data Declarations • A set of QNames of service data elements to which a requestor may subscribe for notification of changes. • A set of SDE that may be used by clients as a parameter • each SDE imply the subscription semantics and notification message that result from the subscription • Operations • Subscribe(SubscriptionExpression, Sink, ExpirationTime) WP3

  7. NotificationSink PortType • Operation • Deliver Notification(Message). • This operation is input only, it does not return an output or faults. [Note: A Web service implementing the NotificationSink portType is not required to be a Grid service.] WP3

  8. NotificationSubscription portType • Service Data Declarations • Current subscriptionExpression managed by this subscription instance • The NotificationSink to which this subscription is delivering messages • Clients use the GridServicePortype operations to manage the subscription (for example subscription.destroy()) WP3

  9. GT3 implementation • OGSI defines abstract interfaces – a pattern or a template. • OGSI notification: open ended interfaces for executing queries and subscribing to notification. • Service instance : interface + binding + implementation • GT3 framework allows to provide own query and notification engine. • GT3 notification : SOAP binding + Java implementation. WP3

  10. Demo based on GT3 implementation • Window1: • GT3 Container of Factories for creating different Grid service instances. • Window2: • NotificationCounter service instance. • keeps the value of an integer as its state. • Also has a SDE named CounterState. • Implements NotificationSource portType • Window3: • A StatusListener service that receives Notification messages whenever the SDE CounterState WP3

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