Consistent snapshots of dynamic heterogeneously managed data

• US 20060036676A1
• Filed: 08/13/2004
• Published: 02/16/2006
• Est. Priority Date: 08/13/2004
• Status: Active Grant

• Current Assignee: ServiceNow Incorporated
• Original Assignee: International Business Machines Corporation
• Inventors: Schade, Andreas, Cardone, Richard J., Hermann, Reto
• Granted Patent: US 7,392,324 B2
• Time in Patent Office: Days
• US Class Current: 709/203
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data
• CPC Class Codes: H04L 45/00 Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00
• CPC Class Codes: H04L 67/75 Indicating network or usage conditions on the user display
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A system and method for providing a consistent view of data stored therein, which can change dynamically in an uncoordinated way, includes a client program and a snapshot server program. The snapshot server program permits one or more client programs to request snapshots of data from the snapshot server program such that the data included in or referenced by a snapshot originates from one or more host server programs and the data is accessible to the snapshot server program, but is managed independently of the snapshot server program.

Claims

1. A system for providing a consistent view of data stored therein, which can change dynamically in an uncoordinated way, comprising:

at least one client program; and

a snapshot server program that permits one or more client programs to request snapshots of data from the snapshot server program such that the data included in or referenced by a snapshot originates from one or more host server programs and the data is accessible to the snapshot server program, but is managed independently of the snapshot server program.

2. The system as recited in claim 1, wherein the snapshot server program creates a snapshot by calculating a current version of data, which is up-to-date to within a propagation delay time.

3. The system as recited in claim 1, wherein the data included in or referenced by the snapshot is in a consistent state.

4. The system as recited in claim 1, wherein the data included in or referenced by the snapshot remains unchanged after the snapshot is created.

5. The system as recited in claim 1, further comprising a snapshot digest associated with each snapshot such that the snapshot digest includes information that describes the version of each datum included in or referenced by the snapshot associated with the digest.

6. The system as recited in claim 5, wherein the snapshot server program associates a digest with each snapshot created by the snapshot server program.

7. The system as recited in claim 5, wherein the snapshot server program creates a snapshot inventory delta using the snapshot digest, the snapshot inventory delta describing what data has changed since the snapshot associated with said digest was created, and classifying each such change as either an insertion, a deletion or an update, and associating the snapshot inventory delta with the digest and with the digest'"'"'s associated snapshot.

8. The system as recited in claim 5, wherein the snapshot includes some of the data provided in the digest associated with the snapshot.

9. The system as recited in claim 5, wherein the snapshot includes references to some of the data described in the digest associated with the snapshot and that the referenced data resides on the snapshot server program or on an accessible host server.

10. The system as recited in claim 5, wherein the snapshot digests are saved to persistent storage and read from persistent storage.

11. The system as recited in claim 5, wherein the snapshot digests are exchanged between programs.

12. The system as recited in claim 1, wherein the host server program permits the snapshot server program to read the host server program'"'"'s data, but the host server program does not coordinate changes to the host server program'"'"'s data with the snapshot server program.

13. The system as recited in claim 1, wherein the host server program permits the snapshot server program to read the host server program'"'"'s data and that the host server program notifies the snapshot server program of changes to the host server program'"'"'s data.

14. The system as recited in claim 1, wherein the at least one client program sends a snapshot digest to the snapshot server program and the snapshot server program responds by sending to the client program a triple that includes a snapshot of a current version of the snapshot server program'"'"'s data, a digest associated with the snapshot and an inventory delta associated with the snapshot.

15. The system as recited in claim 14, wherein the snapshot digest sent by the at least one client program is associated with a snapshot being used by the at least one client program.

16. The system as recited in claim 14, wherein the snapshot digest sent by the at least one client program is null (or empty) and the inventory delta returned by the snapshot server program describes as new all data in the inventory delta'"'"'s associated snapshot.

17. The system as recited in claim 14, further comprising a change threshold parameter, the parameter being sent with the digest to the snapshot server program such that the snapshot server program responds with the triple only if an amount of change in the snapshot server program'"'"'s data since the snapshot associated with the digest was created exceeds a threshold set by the parameter.

18. The system as recited in claim 17, wherein the change threshold includes a number of insertions, deletions and updates.

19. The system as recited in claim 1, wherein the at least one client program sends a pair that includes a snapshot digest and a removed watch list to the snapshot server program and the snapshot server program responds by sending to the client program a triple that includes a snapshot of the current version of the snapshot server program'"'"'s data, a digest associated with the snapshot and an inventory delta associated with the snapshot such that only data that appears in the removed watch list is described as removed in the inventory delta.

20. The system as recited in claim 1, wherein the snapshot server program supports a publish/subscribe interface that permits client programs to be notified when a current version of the snapshot server program'"'"'s data has changed.

21. A system for providing a consistent view of data stored therein, which can change dynamically in an uncoordinated way comprising:

a snapshot server program that permits one or more client programs to request snapshots of data from the snapshot server program, the snapshot server program responding to a request by providing;

a digest with each snapshot created by the snapshot server program, the digest including information that describes a version of each datum included in or referenced by the snapshot associated with the digest; and

a snapshot inventory delta created by the snapshot server program using the snapshot digest, the snapshot inventory delta describing what data has changed since the snapshot associated with the digest was created, and classifying each such change as either an insertion, a deletion or an update, and associating the snapshot inventory delta with the digest and with the digest'"'"'s associated snapshot.

22. The system as recited in claim 21, wherein the data included in or referenced by a snapshot originates from one or more host server programs and the data is accessible to the snapshot server program, but is managed independently of the snapshot server program.

23. The system as recited in claim 21, wherein the snapshot server program creates a snapshot by calculating a current version of data, which is up-to-date to within a propagation delay time.

24. The system as recited in claim 21, wherein the data included in or referenced by the snapshot is in a consistent state.

25. The system as recited in claim 21, wherein the data included in or referenced by the snapshot remains unchanged after the snapshot is created.

26. The system as recited in claim 21, wherein the snapshot includes some of the data provided in the digest associated with the snapshot.

27. The system as recited in claim 21, wherein the snapshot includes references to some of the data described in the digest associated with the snapshot and that the referenced data resides on the snapshot server program or an accessible host server.

28. The system as recited in claim 21, wherein the snapshot digests are saved to persistent storage and read from persistent storage.

29. The system as recited in claim 21, wherein the snapshot digests are exchanged between programs.

30. The system as recited in claim 21, wherein the host server program permits the snapshot server program to read the host server program'"'"'s data, but the host server program does not coordinate changes to the host server program'"'"'s data with the snapshot server program.

31. The system as recited in claim 21, wherein the host server program permits the snapshot server program to read the host server program'"'"'s data and that the host server program notifies the snapshot server program of changes to the host server program'"'"'s data.

32. The system as recited in claim 21, wherein the client program sends a previous snapshot digest to the snapshot server program and the snapshot server program responds by sending to the client program a triple that includes a snapshot of a current version of the snapshot server program'"'"'s data, a digest associated with the snapshot and an inventory delta associated with the snapshot.

33. The system as recited in claim 32, further comprising a change threshold parameter, the parameter being sent with the digest to the snapshot server program such that the snapshot server program responds with the triple only if an amount of change in the snapshot server program'"'"'s data since the snapshot associated with the digest was created exceeds a threshold set by the parameter.

34. The system as recited in claim 33, wherein the change threshold includes a number of insertions, deletions and updates.

35. The system as recited in claim 21, wherein the snapshot digest sent by the client program is null (or empty) and the inventory delta returned by the snapshot server program describes as new all data in the inventory delta'"'"'s associated snapshot.

36. The system as recited in claim 21, wherein the client program sends a pair that includes a snapshot digest and a removed watch list to the snapshot server program and the snapshot server program responds by sending to the client program a triple that includes a snapshot of the current version of the snapshot server program'"'"'s data, a digest associated with the snapshot and an inventory delta associated with the snapshot such that only data that appears in the removed watch list is described as removed in the inventory delta.

37. The system as recited in claim 21, wherein the snapshot server program supports a publish/subscribe interface that permits client programs to be notified when a current version of the snapshot server program'"'"'s data has changed.

38. A method for requesting snapshots of data from a snapshot server program, comprising the steps of:

creating a snapshot by calculating a current version of data, which is up-to-date to within a well-defined propagation delay, the data in or referenced by the snapshot being in a consistent state and unchanged after the snapshot is created;

associating a snapshot digest with each snapshot created such that the snapshot digest includes information that describes the version of each datum included in or referenced by the snapshot associated therewith; and

using the snapshot digest, creating a snapshot inventory delta, which describes what data has changed since the snapshot associated with the digest was created, classifies each such change as either an insertion, a deletion or an update, and associates said inventory delta with said digest and with said digest'"'"'s associated snapshot.

39. The method as recited in claim 38, wherein the data included in or referenced by a snapshot originates from one or more host server programs such that the data is accessible to the snapshot server program, but that the data is managed independently of the snapshot server program.

40. The method as recited in claim 38, wherein the snapshot includes some of the data described in the digest associated with the snapshot.

41. The method as recited in claim 38, wherein the snapshot includes references to some of the data described in the digest associated with said snapshot and the referenced data resides on the snapshot server program or a host server.

42. The method as recited in claim 38, further comprising the step of a host server program permitting the snapshot server program to read the host server program'"'"'s data, but that the host server program does not coordinate changes to the host server program'"'"'s data with the snapshot server program.

43. The method as recited in claim 38, further comprising the step of a host server program permitting the snapshot server program to read the host server program'"'"'s data and that the host server program notifies the snapshot server program of changes to the host server program'"'"'s data.

44. The method as recited in claim 38, further comprising the step of saving and reading the snapshot digests to and from persistent storage.

45. The method as recited in claim 38, further comprising the step of exchanging snapshot digests between programs.

46. The method as recited in claim 38, further comprising the step of sending, from the client program, a snapshot digest to the snapshot server program and the snapshot server program responding by sending to the client program a triple that includes a snapshot of the current version of the server program'"'"'s data, the snapshot'"'"'s associated digest and the snapshot'"'"'s associated inventory delta.

47. The method as recited in claim 46, further comprising the step of providing a change threshold parameter, which is sent with the digest to the snapshot server program such that the snapshot server program responds with the triple only if an amount of change in the snapshot server program'"'"'s data since the snapshot associated with the digest was created exceeds a threshold.

48. The method as recited in claim 38, wherein the amount of change of the threshold includes a number of insertions, deletions and updates.

49. The method as recited in claim 38, further comprising the step of associating the snapshot digest sent by the client program with a snapshot being used by the client program.

50. The method as recited in claim 38, further comprising the step of describing all data in the inventory delta'"'"'s associated snapshot as being new when the snapshot digest sent by the client program is null (or empty).

51. The method as recited in claim 38, further comprising the step of sending a pair from the client program that includes the snapshot digest and a removed watch list to the snapshot server program and the snapshot server program responds by sending to the client program a triple that includes a snapshot of the current version of said server program'"'"'s data, the snapshot'"'"'s associated digest and the snapshot'"'"'s associated inventory delta such that only data that appears in the removed watch list is described as removed in the inventory delta.

52. The method as recited in claim 38, further comprising the step of the snapshot server program supporting a publish/subscribe interface that permits client programs to be notified when the current version of said snapshot server program'"'"'s data has changed.

53. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for requesting snapshots of data from a snapshot server program, as recited in claim 38.