Background cache synchronization

• US 6,553,409 B1
• Filed: 07/09/1999
• Issued: 04/22/2003
• Est. Priority Date: 07/09/1999
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Ellerman, E. Castedo, Zhang, Danpo, Cohen, Josh, Dujari, Rajeev
• Primary Examiner(s): Wiley, David
• Assistant Examiner(s): NEURAUTER, GEORGE C
• Application Number:
  US09/350,331
• Time in Patent Office: 1,383 Days
• Field of Search: 709/213, 709/214, 709/231, 709/235, 709/246, 709/310, 345/512, 345/541, 711/147, 711/118, 711/141, 711/144, 711/154, 725/115-117, 725/131
• US Class Current: 709/213
• CPC Class Codes: G06F 12/0815 Cache consistency protocols
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache

Abstract

Two new cache control headers in the cache control header, “post-check” and “pre-check”, enable the display of content from the cache, with a later synchronization of the content performed in the background via a conditional request such as an IMS request. These headers enable the server to define a non-validate time period relative to the cached content'"'"'s age in which the user will receive content from the cache, a background synchronization period in which the user will receive content from the cache and automatically queue a request for background synchronization thereof, and a validate period in which the cached content may or may not be used, depending on a response to a validation request sent to the server. The content is quickly rendered for the user in the non-validate and background synchronization periods, and the hit count is correct in the background synchronization and validate periods. In the background synchronization time period, the user has a fast experience with rapidly rendered content, while via the background synchronization, the server receives the proper number of hits.

Claims

1. A computer-readable medium including computer-executable instructions for performing steps comprising,

maintaining information with cached content indicative of a state for using and synchronizing the cached content;

receiving a request for content corresponding to the cached content;

comparing current state information to the state for using and synchronizing the cached content, and if the state for using and synchronizing is achieved relative to the current state information, using the cached content without waiting for a synchronization result and outputting a request to synchronize the content.

2. The computer-readable medium of claim 1 wherein the state for using and synchronizing the cached content corresponds to a time period, and wherein comparing current state information includes evaluating the age of the cached content with respect to the time period.

3. The computer-readable medium of claim 2, wherein the information indicative of a state for using and synchronizing the cached content comprises, a post-check variable that specifies a first time parameter, and a pre-check variable that specifies a second time parameter.

4. The computer-readable medium of claim 3, wherein comparing current time information to the time for using and synchronizing the cached content and determining if the time is achieved comprises determining whether the current state information corresponds to a time between the first time parameter and the second time parameter.

5. The computer-readable medium of claim 1 wherein outputting a request includes queuing a task corresponding to the request to synchronize the content.

6. The computer-readable medium of claim 5, wherein the task is queued in a FIFO queue.

7. The computer-readable medium of claim 5 including further computer-executable instructions for, dequeuing the request to synchronize the content.

8. The computer-readable medium of claim 7, wherein the request to synchronize the content is dequeued according to a set of criteria.

9. The computer-readable medium of claim 8, wherein the criteria includes a time duration during which there is no request for content.

10. The computer-readable medium of claim 1 including further computer-executable instructions for synchronizing the content.

11. The computer-readable medium of claim 1 including further computer executable instructions for, associating information with the cached content indicative of a second state for using and not synchronizing the cached content.

12. The computer-readable medium of claim 11 including further computer executable instructions for, comparing current state information to the second state for using and not synchronizing the cached content, and if the second state is achieved, using the cached content.

13. The computer-readable medium of claim 12, wherein the information indicative of a second state for using and not synchronizing the cached content comprises, a variable associated with the cached content that specifies a time parameter.

14. The computer-readable medium of claim 1, wherein associating information with cached content comprises, including in a cache control header associated with the cached content a post-check header extension that specifies a first time parameter and a pre-check header extension that specifies a second time parameter.

15. The computer-readable medium of claim 14, wherein the cache control header further includes an expires header.

16. The computer-readable medium of claim 15 having further computer-executable instructions for determining whether the post-check header extension or the pre-check header extension is present, and if neither are present, utilizing the expires header.

17. The computer-readable medium of claim 1 wherein using the content includes rendering an image therefrom.

18. A method for selectively using cached content, comprising,

maintaining information associated with cached content, the information indicative of a state for using and synchronizing the cached content;

receiving a request for content corresponding to the cached content; and

determining from current state information whether the state for using and synchronizing the cached content is achieved relative to the current state information, and if the state is achieved, using the cached content without waiting for a synchronization result and synchronizing the content in a background operation.

19. The method of claim 18 wherein synchronizing the content in a background operation includes queuing a task.

20. The method of claim 19 wherein synchronizing the content in a background operation includes dequeuing the task and providing a conditional request to a server to synchronize the content.

21. The method of claim 20 wherein synchronizing the content in a background operation includes receiving a response from the server indicating that the content is valid.

22. The method of claim 20 wherein synchronizing the content in a background operation includes receiving updated content from the server.

23. The method of claim 18 wherein using the content includes rendering an image therefrom.

24. The method of claim 18 wherein maintaining information associated with cached content includes maintaining data in association with the content that specifies a time period as the state for using and synchronizing the cached content.

25. The method of claim 24 wherein the data comprises a post-check extension and a pre-check extension of an HTTP header.

26. The method of claim 24 wherein the data further comprises expiry information.

44. A computer-readable medium including computer-executable instructions for performing the method of claim 18.

27. In a computer system, a system for synchronizing content and returning requested content, comprising:

a cache with content stored therein; and

a cache manager mechanism for receiving a request for content corresponding to the cached content and for evaluating information associated with the cached content indicative of a state for using and synchronizing the cached content, the cache manager mechanism comparing current state information to the state for using and synchronizing the cached content, and if the state is achieved relative to the current state information, returning the cached content without waiting for a synchronization result and outputting a request to synchronize the content.

28. The system of claim 27 wherein the content is network content of a server.

29. The system of claim 27 wherein the request for content is made by an operating system or application.

30. The system of claim 27 wherein the information indicative of a state specifies a time period.

31. The system of claim 30, wherein the information associated with the cached content comprises a post-check header that defines a first time parameter and a pre-check header that defines a second time parameter which together specify the time period, and wherein the mechanism for comparing current state information to the state for using and synchronizing the cached content determines whether a time corresponding to the current state is within the time period.

32. The system of claim 27 further comprising a data structure, and wherein the cache manager outputs the request to synchronize the content into the data structure.

33. The system of claim 32 wherein the data structure comprises a queue.

34. The system of claim 33 wherein the queue comprises a FIFO queue.

35. The system of claim 32 further comprising a mechanism for removing the request from the data structure and for sending the request to a content server.

36. The system of claim 35 wherein the mechanism is a dequeuing mechanism that dequeues the request for content based on criteria being met.

37. The system of claim 35 wherein the criteria includes a time duration.

38. The system of claim 36 wherein the criteria includes an operating state of the system.

39. In a computer system, a method of specifying how cached content may be synchronized, comprising,

providing information indicative of a state wherein cached content may be used

without waiting for a synchronization result and a request for synchronization thereof output;

and

associating the information with the content such that if the state is achieved relative to current state information, the cached content will be used without waiting for a synchronization result and a request for synchronization of the content will be output.

40. The method of claim 39, wherein the information is associated with the content via an HTTP header.

41. The method of claim 39, wherein the information comprises a post-check header and a pre-check header to specify a time period in which cached content may be used and a request for synchronization thereof output.

42. The method of claim 39 further comprising, downloading the content and information associated therewith to a client.

43. The method of claim 42 further comprising, receiving the content and information at a client, evaluating a current state at the client, and if the current state corresponds to the state wherein cached content may be used and a request for synchronization thereof output, using the cached content and requesting synchronization thereof at the client.

45. A computer-readable medium including computer-executable instructions for performing the method of claim 39.