Efficient locking of shared data that is accessed for reads in a cluster database

• US 7,447,786 B2
• Filed: 05/05/2006
• Issued: 11/04/2008
• Est. Priority Date: 05/09/2003
• Status: Expired due to Term

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Macnaughton, Neil, Chandrasekaran, Sashikanth, Loaiza, Juan
• Primary Examiner(s): Coulter; Kenneth R
• Application Number:
  US11/418,782
• Publication Number:
  US 20060212573A1
• Time in Patent Office: 914 Days
• Field of Search: 709/229, 710/200
• US Class Current: 709/229
• CPC Class Codes: G06F 15/16 Combinations of two or more digital computers each having at least an arithmetic unit, a program unit and a register, e.g. for a simultaneous processing of several programs coordinating program control therefor G06F9/52; in regulating and control system G05B
• CPC Class Codes: G06F 15/173 using an interconnection network, e.g. matrix, shuffle, pyramid, star, snowflake
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms

Abstract

Described herein are techniques for synchronizing access to resources in a multi node system by establishing a resource as a read-mostly resource based on one or more criteria, and allowing a node to acquire a shared lock, not granted by the master, on the read-mostly resource where no anti-lock exists for the resource.

Claims

1. A computer implemented method for managing access to a resource in a multi-node system comprising a plurality of nodes, wherein each of the plurality of nodes includes one or more processors, the method comprising the steps of:

establishing the resource as a read-mostly resource based on one or more criteria, wherein a first node of plurality of nodes is master of the resource;

the master receiving a request for an exclusive lock on the resource;

in response to the master receiving the request for an exclusive lock, the master issuing an anti-lock for the resource to all other nodes of the plurality of nodes; and

in response to a second node being issued a respective anti-lock for the resource, the second node preventing issuance of a read-mostly lock on the resource while the second node holds the anti-lock.

2. The method of claim 1, further comprising:

converting the read-mostly lock on the resource into a lock granted by the master; and

closing all anti-locks on the resource.

3. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 2.

4. The method of claim 1, wherein the criteria is based on access patterns.

5. The method of claim 4, wherein:

the criteria based on access patterns includes information related to accesses;

wherein the information related to accesses comprises a mapping of object numbers to the number of read locks and write locks that have been granted to each instance.

6. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 5.

7. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 4.

8. The method of claim 1, further comprising:

granting an object affinity lock on the resource, wherein the resource has affinity to the requesting instance.

9. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 8.

10. The method of claim 1, wherein the anti-lock is issued to a newly-joined node.

11. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 10.

12. The method of claim 1, wherein the anti-lock issued to the other nodes is remastered among all surviving nodes upon the death of the node.

13. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 12.

14. The method of claim 1, further comprising the second node relinquishing the anti-lock in response to a command from the master.

15. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 14.

16. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 1.

17. A computer implemented method for managing access to a resource in a multi-node system comprising a plurality of nodes, wherein each of the plurality of nodes includes one or more processors, the method comprising the steps of:

establishing the resource as a read-mostly resource based on one or more criteria, wherein a first node of plurality of nodes is master of the resource;

based on the resource being established as a read-mostly resource, a second node of the plurality of nodes acquiring a shared lock, not granted by the master, on the resource;

the master receiving a request for an exclusive lock on the resource;

in response to the master receiving the request for an exclusive lock, the master issuing an anti-lock for the resource to all other nodes of the plurality of nodes; and

in response to the second node being issued a respective anti-lock for the resource, the second node;

relinquishing the shared lock; and

refraining from issuing a read-mostly lock on the resource while the second node holds the anti-lock.

18. The method of claim 17, wherein the resource is a data block.

19. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 18.

20. The method of claim 17, further comprising:

partitioning the resource into a plurality of portions; and

for each portion of said resource, allocating an anti-lock in each node for each portion on which an exclusive lock is held by any node.

21. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 20.

22. A computer implemented method for managing access to a resource in a multi-node system comprising a plurality of nodes, wherein each of the plurality of nodes includes one or more processors, the method comprising the steps of:

establishing a first node of plurality of nodes as master of the resource;

wherein, as master of the resource, the first node is the only node of said multi-node system authorized to grant exclusive locks on the resource;

while said first node is the master of the resource, a second node of the plurality of nodes granting a read-mostly lock on the resource, wherein at the time the second node grants the read-mostly lock on the resource, the second node does not hold a lock, on the resource, granted by the master of the resource; and

wherein the first node is a different node than the second node.

23. The method of claim 22 wherein:

the method further comprises the step of, while the first node is master of the resource and the read-mostly lock granted by the second node on the resource is being held, a third node of the plurality of nodes granting another read-mostly lock on the resource;

at the time the third node grants the other read-mostly lock on the resource, the third node does not hold a lock, on the resource, granted by the master of the resource; and

the third node is a different node from both the second node and the first node.

24. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 22.

25. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 23.

26. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the steps of:

establishing the resource as a read-mostly resource based on one or more criteria, wherein a first node of plurality of nodes is master of the resource;

based on the resource being established as a read-mostly resource, a second node of the plurality of nodes acquiring a shared lock, not granted by the master, on the resource;

the master receiving a request for an exclusive lock on the resource;

in response to the master receiving the request for an exclusive lock, the master issuing an anti-lock for the resource to all other nodes of the plurality of nodes; and

in response to the second node being issued a respective anti-lock for the resource, the second node;

relinquishing the shared lock; and

refraining from issuing a read-mostly lock on the resource while the second node holds the anti-lock.