Masterless locks in a multi-node environment

• US 7,340,743 B1
• Filed: 04/25/2003
• Issued: 03/04/2008
• Est. Priority Date: 04/25/2003
• Status: Active Grant

• Current Assignee: Veritas Technologies, LLC (Whitehouse Group Ltd.)
• Original Assignee: Symantec Operating Corporation (NortonLifeLock Inc.)
• Inventors: Anural, Anurag, Balan, Ramesh, Nagaraj, Murali, Kumaresan, Balemurughan, Prince, Harold Bailey Jr.
• Primary Examiner(s): Thomson; William
• Assistant Examiner(s): WU, QING YUAN
• Application Number:
  US10/423,146
• Time in Patent Office: 1,775 Days
• Field of Search: 709217-219, 709/223, 709225-226, 726/2, 726/3, 718/104, 707/8, 710/200, 710/28, 710/36, 711/150, 711/152
• US Class Current: 718/104
• CPC Class Codes: G06F 2209/522 Manager
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database

Abstract

A method, system, application programming interface, computer system, and computer program product to provide locks for controlling access to data by nodes in a multi-node environment while minimizing messages sent between nodes. Based upon knowledge of lock usage in the multi-node environment, a multi-node knowledge agent can determine when no other node is accessing data protected by a given lock, as well as when an event has occurred that precedes a request by another node to access data protected by the given lock. When no other node is accessing data and no such event has occurred, the multi-node knowledge agent can designate that given lock as “masterless.” A lock agent on the node hosting the multi-node knowledge agent is authorized to subsequently grant access to the data protected by the masterless lock to clients on that node without communicating with a lock master, which may reside at another node.

Claims

1. A method comprising:

determining that none of a plurality of nodes is accessing data protected by a lock;

determining, for at least all but a first node of the plurality of nodes, that no event has occurred preceding a request to access the data protected by the lock;

requesting termination of a lock master for the lock, in response to determining that none of the plurality of nodes is accessing data protected by the lock and that, for at least all but the first node of the plurality of nodes, no event has occurred preceding the request to access data protected by the lock;

granting access to the data protected by the lock to clients of the first node; and

authorizing the first node to raise an access level for the lock.

2. The method of claim 1 wherein

the lock is a masterless lock.

3. The method of claim 1 wherein

raising the access level comprises at least one of:

changing the access level from shared access to exclusive access;

changing the access level from no access to shared access; and

changing the access level from no access to exclusive access.

4. The method of claim 1 further comprising:

if a type of the lock is not masterless, changing the type of the lock to masterless.

5. The method of claim 1 further comprising:

changing a type of the lock based upon a change to an access level of a second lock.

6. The method of claim 1 further comprising:

changing a type of the lock based upon a change to an access level of a block comprising a plurality of locks, wherein

the block comprises the lock.

7. The method of claim 1 further comprising:

determining that an event has occurred, wherein

the event precedes a request to raise the access level by a second node of the plurality of nodes.

8. The method of claim 1 further comprising:

subsequently changing a type of the lock such that communicating with a second node is required to raise the access level; and

requesting a new lock master for the lock.

9. The method of claim 8 wherein

the subsequently changing the type of the lock occurs when an event occurs that precedes a request by a third node of the plurality of nodes to raise the access level for the lock.

10. The method of claim 9 wherein

the third node and the second node are the same node.

11. The method of claim 9 wherein

the subsequently changing the type of the lock comprises:

changing the type of the lock to normal.

12. The method of claim 1 further comprising:

granting access to the data protected by the lock to clients of the first node without communicating with another node of the plurality of nodes.

13. A computer system comprising:

a processor for executing instructions;

a memory to store the instructions, wherein the instructions comprise instructions for;

determining that none of a plurality of nodes is accessing data protected by a lock;

determining, for at least all but a first node of the plurality of nodes, that no event has occurred preceding a request to access the data protected by the lock;

requesting termination of a lock master for the lock, in response to determining that none of the plurality of nodes is accessing data protected by the lock and that, for at least all but the first node of the plurality of nodes, no event has occurred preceding the request to access data protected by the lock;

granting access to the data protected by the lock to clients of the first node; and

authorizing the first node to raise an access level for the lock.

14. The computer system of claim 13 wherein the instructions further comprise instructions for:

changing a type of the lock to masterless.

15. The computer system of claim 13 wherein the instructions further comprise instructions for:

determining that an event has occurred, wherein

the event precedes a request to raise the access level by a second node of the plurality of nodes.

16. The computer system of claim 15 further comprising instructions for:

changing a type of the lock upon determining that the event has occurred such that communicating with the second node is required to raise the access level.

17. A computer-readable medium comprising instructions for:

determining that none of a plurality of nodes is accessing data protected by a lock;

determining, for at least all but a first node of the plurality of nodes, that no event has occurred preceding a request to access the data protected by the lock;

requesting termination of a lock master for the lock, in response to determining that none of the plurality of nodes is accessing data protected by the lock and that, for at least all but the first node of the plurality of nodes, no event has occurred preceding it the request to access data protected by the lock;

granting access to the data protected by the lock to clients of the first node; and

authorizing the first node to raise an access level for the lock.

18. The computer-readable medium of claim 17 further comprising instructions for:

changing a type of the lock to masterless.

19. The computer-readable medium of claim 17 further comprising instructions for:

determining that an event has occurred, wherein

the event precedes a request to raise the access level by a second node of the plurality of nodes.

20. The computer-readable medium of claim 19 further comprising instructions for:

changing a type of the lock upon determining that the event has occurred such that communicating with the second node is required to raise the access level.