Electrical computers and digital processing systems: multicomput – Distributed data processing – Client/server
Reexamination Certificate
2001-07-27
2003-08-05
Geckil, Mehmet B. (Department: 2192)
Electrical computers and digital processing systems: multicomput
Distributed data processing
Client/server
C709S217000, C707S793000
Reexamination Certificate
active
06604127
ABSTRACT:
The following identified U.S. patent applications are relied upon and are incorporated by reference in this application.
U.S. Provisional Application No. 60/138,680, entitled “Jini™ Technology Helper Utilities and Services,” filed on Jun. 14, 1999.
Provisional U.S. Patent Application No. 60/076,048, entitled Distributed Computing System,” filed on Feb. 26, 1998.
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U.S. patent application Ser. No. 09/044,826, entitled “Method and System for Facilitating Access to a Lookup Service,” filed on Mar. 20, 1998.
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FIELD OF THE INVENTION
The present invention relates generally to data processing systems and, more particularly to a dynamic lookup service in a distributed system.
BACKGROUND OF THE INVENTION
A lookup service contains an indication of where network services are located within a distributed system comprised of multiple machines, such as computers and related peripheral devices, connected in a network (for example, a local area network, wide area network, or the Internet). A “network service” refers to a resource, data, or functionality that is accessible on the network. Typically, for each service, the lookup service contains an address used by a client (e.g., a program) to access the service (e.g., a printer).
Conventional lookup services are static: whenever updates to the lookup service are needed to either add a new service or delete an existing service, the lookup service is taken offline, rendering the lookup service inaccessible, and then, the lookup service is manually updated by the system administrator. During the time when the lookup service is offline, clients in the distributed system are unable to access the lookup service and any of its network services. Another limitation of conventional lookup services is that, when updated, clients are not made aware of the updates to the lookup service until they explicitly perform a refresh operation, which downloads the latest service information to the clients. Before such a refresh, however, if a client requests a service that is no longer available, an error occurs which may cause the client to hang. Also, before a refresh, the client is not aware of any new services that have been recently added to the lookup service. It is therefore desirable to improve lookup services for distributed systems.
SUMMARY OF THE INVENTION
Systems consistent with the present invention provide an improved lookup service that allows for the dynamic addition and deletion of services. This lookup service allows for the update, i.e., addition and deletion of available services automatically, without user intervention. As a result, clients of the lookup service may continue using the lookup service and its associated services while the updates occur. Additionally, the lookup service provides a notification mechanism that can be used by clients to receive a notification when the lookup service is updated. By receiving such a notification, clients can avoid attempting to access a service that is no longer available and can make use of new services as soon as they are added to the lookup service.
In accordance with methods consistent with the present invention, a method is provided in a data processing system having a lookup service with associated services. This method receives a request by the lookup service for notification when the lookup service is updated, determines when the lookup service is updated, and generates a notification when it is determined that the lookup service is updated.
In accordance with methods consistent with the present invention, a method is provided in a data processing system having a lookup service with associated services. This method sends a request to the lookup service to be notified when the lookup service is updated and receives an indication that the lookup service has been updated.
In accordance with methods consistent with the present invention, a method is provided in a data processing system having a lookup service with associated services and a client lookup manager with an associated cache. This method transmits an event by the lookup service that identifies a change to one of the associated network services. The client lookup manager receives the event and updates the associated cache to reflect the change.
In accordance with methods consistent with the present invention, a method is provided in a data processing system having a client and lookup service with associated services. This method receives a request from a client for access to a network service, then retrieves a reference from a cache reflecting a particular network service corresponding to the requested network service and transmits the reference to the client.
In accordance with systems consistent with the present invention, a data processing system comprising a memory and a processor is provided. The memory includes a lookup service containing indications of services that are available for use, a first client for updating the lookup service, and a second client for utilizing the lookup service while the first client is updating the lookup service. The processor runs the lookup service, the first client, and the second client.
In accordance with systems consistent with the presen
Arnold Kenneth C. R. C.
Murphy Brian T.
Pan Zane
Scheifler Robert W.
Waldo James H.
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