Method and apparatus for synchronizing caches in a distributed computing system

• US 20040003177A1
• Filed: 07/01/2002
• Published: 01/01/2004
• Est. Priority Date: 07/01/2002
• Status: Active Grant

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Goff, Max K.
• Granted Patent: US 6,836,825 B2
• Time in Patent Office: Days
• US Class Current: 711/136
• CPC Class Codes: G06F 12/0815 Cache consistency protocols
• CPC Class Codes: G06F 16/9574 of access to content, e.g. by caching

Abstract

One embodiment of the present invention provides a system for synchronizing a cache in a computer system through a peer-to-peer refreshing operation. During operation, the system determines the age of an entry in the cache. If the age of the entry exceeds a life span for the entry, the system invalidates the entry in the cache. The system subsequently refreshes the entry by retrieving an updated version of the entry from a peer of the computer system, if possible, instead of from a centralized source for the entry.

Claims

1. A method for synchronizing an entry in a cache in a computer system through a peer-to-peer refreshing operation, comprising:

determining the age of the entry in the cache within the computer system; and

if the age of the entry exceeds a life span for the entry,

invalidating the entry in the cache, and

refreshing the entry by retrieving an updated version of the entry from a peer of the computer system, if possible, instead of from a centralized source for the entry.

2. The method of claim 1, wherein determining the age of the entry involves determining the age of the entry with reference to a time value extracted from a Global Positioning System (GPS) signal.

3. The method of claim 1, further comprising determining the life span for the entry based upon a taxonomy of data that associates different life spans with different types of data.

4. The method of claim 1, wherein refreshing the entry involves waiting until the entry is accessed again before retrieving the updated version of the entry.

5. The method of claim 1, wherein refreshing the entry involves automatically refreshing the entry without waiting until the entry is accessed again.

6. The method of claim 1, wherein refreshing the entry involves:

attempting to retrieve the updated version of the entry from a first-order peer, which is part of the same peer group as the computer system; and

if the updated version of the entry cannot be retrieved from a first-order peer, attempting to retrieve the updated version of the entry from a second-order peer, which is accessible through a first order peer.

7. The method of claim 1, wherein if the updated version of the entry cannot be retrieved from a peer of the computer system, the method further comprises retrieving the updated version of entry from the centralized source for the entry.

8. The method of claim 1, wherein if a given peer of the computer system subsequently requests the updated version of the entry, the method further comprises supplying the updated version of the entry to the given peer.

9. The method of claim 1, wherein retrieving the updated version of the entry involves using a Juxtapose (JXTA) framework to facilitate peer-to-peer communications to retrieve the entry.

10. A computer-readable storage medium storing instructions that when executed by a computer system cause the computer system to perform a method for synchronizing an entry in a cache in the computer system through a peer-to-peer refreshing operation, the method comprising:

determining the age of the entry in the cache within the computer system; and

if the age of the entry exceeds a life span for the entry,

invalidating the entry in the cache, and

refreshing the entry by retrieving an updated version of the entry from a peer of the computer system, if possible, instead of from a centralized source for the entry.

11. The computer-readable storage medium of claim 10, wherein determining the age of the entry involves determining the age of the entry with reference to a time value extracted from a Global Positioning System (GPS) signal.

12. The computer-readable storage medium of claim 10, wherein the method further comprises determining the life span for the entry based upon a taxonomy of data that associates different life spans with different types of data.

13. The computer-readable storage medium of claim 10, wherein refreshing the entry involves waiting until the entry is accessed again before retrieving the updated version of the entry.

14. The computer-readable storage medium of claim 10, wherein refreshing the entry involves automatically refreshing the entry without waiting until the entry is accessed again.

15. The computer-readable storage medium of claim 10, wherein refreshing the entry involves:

attempting to retrieve the updated version of the entry from a first-order peer, which is part of the same peer group as the computer system; and

if the updated version of the entry cannot be retrieved from a first-order peer, attempting to retrieve the updated version of the entry from a second-order peer, which is accessible through a first order peer.

16. The computer-readable storage medium of claim 10, wherein if the updated version of the entry cannot be retrieved from a peer of the computer system, the method further comprises retrieving the updated version of entry from the centralized source for the entry.

17. The computer-readable storage medium of claim 10, wherein if a given peer of the computer system subsequently requests the updated version of the entry, the method further comprises supplying the updated version of the entry to the given peer.

18. The computer-readable storage medium of claim 10, wherein retrieving the updated version of the entry involves using a Juxtapose (JXTA) framework to facilitate peer-to-peer communications to retrieve the entry.

19. An apparatus that synchronizes an entry in a cache in a computer system through a peer-to-peer refreshing operation, comprising:

an age determining mechanism that is configured to determine the age of the entry in the cache within the computer system; and

a refreshing mechanism, wherein if the age of the entry exceeds a life span for the entry, the refreshing mechanism is configured to,

invalidate the entry in the cache, and to

refresh the entry by retrieving an updated version of the entry from a peer of the computer system, if possible, instead of from a centralized source for the entry.

20. The apparatus of claim 19, wherein the age determining mechanism is configured to determine the age of the entry with reference to a time value extracted from a Global Positioning System (GPS) signal.

21. The apparatus of claim 19, further comprising a life span determining mechanism that is configured to determine the life span for the entry based upon a taxonomy of data that associates different life spans with different types of data.

22. The apparatus of claim 19, wherein the refreshing mechanism is configured to wait until the entry is accessed again before retrieving the updated version of the entry.

23. The apparatus of claim 19, wherein the refreshing mechanism is configured to automatically refreshing the entry without waiting until the entry is accessed again.

24. The apparatus of claim 19, wherein the refreshing mechanism is configured to:

attempt to retrieve the updated version of the entry from a first-order peer, which is part of the same peer group as the computer system; and

to

attempt to retrieve the updated version of the entry from a second-order peer, which is accessible through a first order peer, if the updated version of the entry cannot be retrieved from a first-order peer.

25. The apparatus of claim 19, wherein if the updated version of the entry cannot be retrieved from a peer of the computer system, the refreshing mechanism is configured to retrieve the updated version of entry from the centralized source for the entry.

26. The apparatus of claim 19, wherein if a given peer of the computer system subsequently requests the updated version of the entry, the refreshing mechanism is configured to supply the updated version of the entry to the given peer.

27. The apparatus of claim 19, wherein the refreshing mechanism is configured to use a Juxtapose (JXTA) framework to facilitate peer-to-peer communications to retrieve the entry.