Lecture notes on cloud computing IV b. Tech-1 st semester prepared by
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| ENHANCING CLOUD COMPUTING ENVIRONMENTS USING A CLUSTER AS Ab bSERVICE RVWS DESIGN Dynamic Attribute Exposure There are two categories of dynamic attributes addressed in the RVWS framework state and characteristic. State attributes cover the current activity of the service and its resources, thus indicating readiness. For example, a Web service that exposes a cluster (itself a complex resource) would most likely have a dynamic state attribute that indicates how many nodes in the cluster are busy and how many are idle. Characteristic attributes cover the operational features of the service, the resources behind it, the quality of service (QoS), price and provider information. Again with the cluster Web service example, a possible characteristic is an array of support software within the cluster. This is important information as cluster clients need to know what software libraries exist on the cluster. To keep the stateful Web service current, a Connector [2] is used to detect changes in resources and then inform the Web service. The Connector has three logical modules Detection, Decision, and Notification. The Detection module routinely queries the resource for attribute information. Any changes in the attributes are passed to the Decision module (3) that decides if the attribute change is large enough to warrant a notification. This prevents excessive communication with the Web service. Updated attributes are passed onto the Notification module (4), which informs the stateful Web service (5) that updates its internal state. When clients requests the stateful WSDL document (6), the Web service returns the WSDL document with the values of all attributes (7) at the request time. |