Method and apparatus for determining status of remote objects in a distributed system

• US 6,598,094 B1
• Filed: 03/20/1998
• Issued: 07/22/2003
• Est. Priority Date: 03/20/1998
• Status: Expired due to Term

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Jones, Peter C., Wollrath, Ann M.
• Primary Examiner(s): Courtenay, III, St. John
• Assistant Examiner(s): BULLOCK JR, LEWIS ALEXANDER
• Application Number:
  US09/044,790
• Time in Patent Office: 1,950 Days
• Field of Search: 709/315, 709/330, 709/310, 709/318, 709/317, 709/332, 709/200, 709/202, 709/201, 709/203, 709/217, 709/219, 707/103.R, 707/103.Z, 707/103.Y
• US Class Current: 719/330
• CPC Class Codes: G06F 12/0261 using reference counting

Abstract

Systems consistent with the present invention a method and apparatus is provided for selectively supplying a state change associated with remote objects in a distributed system. The method involves registering a request from a computational entity to receive notification as to a state change associated with a remote object. Registration of a notification request causes the creation of a remote weak reference to the remote object including an identifier of a location of the remote object. Periodically, a request is sent to a location based on the identifier of the remote weak reference. When it is determined that a state change associated with the remote object has occurred, the registered computational entity is notified accordingly.

Claims

1. A method for supplying a state change associated with remote objects in a distributed system comprised of multiple platforms, wherein computational entities maintain references indicating the location of objects within the distributed system, the method comprising:

providing an object resident on a first platform;

registering a request from a computational entity located on a second platform remote with respect to the first platform to receive an indication reflecting a state change associated with the object, wherein the registering step is performed by a processor operating in the second platform and includes;

receiving a strong reference to the object from the computational entity, and

creating a remote weak reference corresponding to the object based on the received strong reference;

determining whether an event has occurred changing the state associated with the object;

locating the one of the platforms upon which the object resides based on the remote weak reference corresponding to the object;

sending a status request to the located platform; and

providing a notification to the computational entity based on the determination.

2. A computer-readable medium containing instructions that perform a method, when executed by a processor, for supplying a state change associated with remote objects in a distributed system comprised of multiple platforms, wherein the method enables computational entities to maintain references indicating the location of objects within the distributed system, by:

providing an object resident on a first platform;

registering a request from a computational entity located on a second platform remote with respect to the first platform to receive an indication reflecting a state change associated with the object, wherein the registering step is performed by a processor operating in the second platform and includes;

receiving a strong reference to the object from the computational entity, and

creating a remote weak reference corresponding to the object based on the received strong reference; and

determining whether an event has occurred changing the state associated with the object;

locating the first platform upon which the object resides based on the remote weak reference corresponding to the object;

sending a status request to the located platform; and

providing a notification to the computational entity based on the determination.

3. A system comprising:

a server system including an object; and

a client system including;

a client process; and

a remote weak reference process configured, when executed by a processor, to;

receive, from the client process, a registration request for receiving an

indication when a state associated with the object changes, the registration request

including a strong reference to the object,

create a remote weak reference to the object, identify the server system based on the remote weak reference, send a status request to the server system to determine whether the state

associated with the object changes, and

provide, to the client process, a notification indicating a change in the state

associated with the object based on the determination.

4. The system of claim 3, wherein the notification is provided to the client process only when it is determined the state associated with the object has changed.

5. The system of claim 3, wherein the remote weak reference process accesses an address space associated with the object to determine whether the state associated with the object changed.

6. The system of claim 5, wherein the remote weak reference process determines that the state associated with the object has changed when a network partition separates an address space associated with the computational entity and the address space associated with the object.

7. The system of claim 3, wherein objects have corresponding references indicating their address space within the distributed system, and wherein the remote weak reference process is configured to determine whether the state associated with the object changes by locating an address space associated with the object based on a reference corresponding to the object and accessing the address space associated with the object.

8. The system of claim 3, wherein the remote weak reference process is configured to receive a liveness notification when the state associated with the object has changed.