CONSISTENCY DOMAINS FOR REPLICATION IN DISTRIBUTED COMPUTING

• US 20120179791A1
• Filed: 01/07/2011
• Published: 07/12/2012
• Est. Priority Date: 01/07/2011
• Status: Active Grant

• Current Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Original Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Inventors: Little, Mark Cameron
• Granted Patent: US 8,639,786 B2
• Time in Patent Office: Days
• US Class Current: 709/221
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores

Abstract

A computing device performs an operation by a first computing device and updates a shared system state on the first computing device based on the operation. The computing device causes the shared system state to be updated on a second computing device using a strongly consistent replication mechanism, wherein the first computing device and the second computing device are members of a first consistency domain. The computing device also causes the shared system state to be updated on a third computing device using a weakly consistent replication mechanism, wherein the third computing device is a member of a second consistency domain.

Claims

1. A method comprising:

performing an operation by a first computing device;

updating a shared system state on the first computing device based on the operation;

causing the shared system state to be updated on a second computing device using a strongly consistent replication mechanism, wherein the first computing device and the second computing device are members of a first consistency domain; and

causing the shared system state to be updated on a third computing device using a weakly consistent replication mechanism, wherein the third computing device is a member of a second consistency domain.

2. The method of claim 1, wherein:

causing the shared system state to be updated on the second computing device comprises sending a first message to the second computing device using the strongly consistent replication mechanism, wherein the first message causes the second computing device to update the shared system state on the second computing device; and

causing the shared system state to be updated on the third computing device comprises sending a second message to the third computing device using the weakly consistent replication mechanism, wherein the second message causes the third computing device to update the shared system state on the third computing device.

3. The method of claim 2, further comprising:

after receiving a response message from the second computing device indicating that the second computing device has updated the shared system state, performing another operation by the first computing device and updating the shared system state on the first computing device, regardless of whether the third computing device has updated the shared system state.

4. The method of claim 1, wherein the weakly consistent replication mechanism includes a gossip communication protocol.

5. The method of claim 1, wherein members of the first consistency domain are strongly consistent with other members of the first consistency domain, members of the second consistency domain are strongly consistent with other members of the second consistency domain, and the members of the second consistency domain are weakly consistent with the members of the first consistency domain.

6. The method of claim 1, wherein the second consistency domain is inconsistent from the first consistency domain by at most a predetermined skew value.

7. The method of claim 6, wherein the predetermined skew value is defined based on a time difference, wherein members of the second consistency domain will achieve a consistent state with members of the first consistency domain within the time difference.

8. A computer readable storage medium including instructions that, when executed by a first computing device, cause the first computing device to perform a method comprising:

performing an operation by the first computing device;

updating a shared system state on the first computing device based on the operation;

causing the shared system state to be updated on a second computing device using a strongly consistent replication mechanism, wherein the first computing device and the second computing device are members of a first consistency domain; and

causing the shared system state to be updated on a third computing device using a weakly consistent replication mechanism, wherein the third computing device is a member of a second consistency domain.

9. The computer readable storage medium of claim 8, wherein:

causing the shared system state to be updated on the second computing device comprises sending a first message to the second computing device using the strongly consistent replication mechanism, wherein the first message causes the second computing device to update the shared system state on the second computing device; and

causing the shared system state to be updated on the third computing device comprises sending a second message to the third computing device using the weakly consistent replication mechanism, wherein the second message causes the third computing device to update the shared system state on the third computing device.

10. The computer readable storage medium of claim 9, the method further comprising:

after receiving a response message from the second computing device indicating that the second computing device has updated the shared system state, performing another operation by the first computing device and updating the shared system state on the first computing device, regardless of whether the third computing device has updated the shared system state.

11. The computer readable storage medium of claim 8, wherein the weakly consistent replication mechanism includes a gossip communication protocol.

12. The computer readable storage medium of claim 8, wherein members of the first consistency domain are strongly consistent with other members of the first consistency domain, members of the second consistency domain are strongly consistent with other members of the second consistency domain, and the members of the second consistency domain are weakly consistent with the members of the first consistency domain.

13. The computer readable storage medium of claim 8, wherein the second consistency domain is inconsistent from the first consistency domain by at most a predetermined skew value.

14. The computer readable storage medium of claim 13, wherein the predetermined skew value is defined based on a time difference, wherein members of the second consistency domain will achieve a consistent state with members of the first consistency domain within the time difference.

15. A system comprising:

a first computing device having a processing device to execute instructions for a hybrid replicator, wherein the instructions cause the processing device to;

perform an operation;

update a shared system state on the first computing device based on the operation;

cause the shared system state to be updated on a second computing device using a strongly consistent replication mechanism, wherein the first computing device and the second computing device are members of a first consistency domain; and

cause the shared system state to be updated on a third computing device using a weakly consistent replication mechanism, wherein the third computing device is a member of a second consistency domain.

16. The system of claim 15, further comprising:

the second computing device, networked with the first computing device, to receive a first message from the first computing device via the strongly consistent replication mechanism, to process the first message to update the shared system state on the second computing device, and to send a response message to the first computing device indicating that the second computing device has updated the shared system state; and

the third computing device, networked with the first computing device, to receive a second message from the first computing device via the weakly consistent replication mechanism, and to process the second message to update the shared system state on the third computing device.

17. The system of claim 16, further comprising the instructions to cause the processing device to:

after receiving a response message from the second computing device indicating that the second computing device has updated the shared system state, perform another operation and update the shared system state on the first computing device, regardless of whether the third computing device has updated the shared system state.

18. The system of claim 15, wherein the weakly consistent replication mechanism includes a gossip communication protocol.

19. The system of claim 15, wherein members of the first consistency domain are strongly consistent with other members of the first consistency domain, members of the second consistency domain are strongly consistent with other members of the second consistency domain, and the members of the second consistency domain are weakly consistent with the members of the first consistency domain.

20. The system of claim 15, wherein the second consistency domain is inconsistent from the first consistency domain by at most a predetermined skew value.