GENERATING DATABASE SEQUENCES IN A REPLICATED DATABASE ENVIRONMENT

• US 20140025634A1
• Filed: 07/11/2013
• Published: 01/23/2014
• Est. Priority Date: 07/18/2012
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Dennehy, Mark, Mooney, Robert
• Granted Patent: US 9,846,733 B2
• Time in Patent Office: Days
• US Class Current: 707/623
• CPC Class Codes: G06F 16/23 Updating
• CPC Class Codes: G06F 16/27 Replication, distribution or synchronisation of data between databases or within a distributed database system; Distributed database system architectures therefor
• CPC Class Codes: G06F 8/658 Incremental updates; Differential updates

Abstract

Embodiments relate to generating database sequences in a replicated database environment. An aspect includes providing a group of nodes each hosting an instance of a replicated database, with one node in the group elected as a master node responsible for generating and distributing values for auto-generated values in a column or row of the replicated database. Another aspect includes dividing, by the master node, a sequence space of possible auto-generated values for the column or row into sub-ranges and assigning a sub-range to a particular node in the group of nodes. Another aspect includes distributing, by the master node, values of the assigned sub-range to a particular node of the group of nodes.

Claims

1. A method for generating database sequences in a replicated database environment, comprising:

providing a group of nodes each hosting an instance of a replicated database, with one node in the group elected as a master node responsible for generating and distributing values for auto-generated values in a column or row of the replicated database;

dividing, by the master node, a sequence space of possible auto-generated values for the column or row into sub-ranges and assigning a sub-range to a particular node in the group of nodes; and

distributing, by the master node, values of the assigned sub-range to a particular node of the group of nodes.

2. The method of claim 1, comprising:

detecting a partition or node failure in the group of nodes;

determining new groups of nodes and electing a new master node in a group of nodes which cannot see an original master node;

dividing, by the original and new master node or nodes, the sequence space of possible auto-generated values into sub-spaces for each group of nodes according to the size of each group of nodes; and

the new master node or nodes assigning a sub-range for a particular node in the group of nodes.

3. The method of claim 2, wherein the original master node and a new master node monitor a network for one another periodically to detect a rectification of a network partition fault.

4. The method of claim 2, wherein based on rectification of a network partition fault occurring, recombining the sequence sub-spaces and reasserting the original master node in the master node role.

5. The method of claim 3, wherein based on a new master node re-joining a group of nodes, the new master node indicates to any other nodes in the new master node'"'"'s group that it is no longer its master node.

6. The method of claim 3, wherein a new group of nodes re-joins a previous group of nodes using the new group'"'"'s master node as a gateway to the original master node.

7. The method of claim 1, wherein the sub-ranges are of variable size, and wherein a size of a sub-range that is assigned to a node is determined based on a speed of allocation of values by the nodes, such that a node which is allocating values faster than other nodes is assigned a larger sub-range than the other nodes.

8. The method of claim 1, wherein a node exhausts a sub-range of values before requesting a further sub-range of values.

9. The method of claim 1, wherein the master node assigns and distributes a sub-range of values for itself.

10. The method of claim 1, wherein the group of nodes have bi-directional replication for databases where more than one node can create records in a replicated table.

11. A system for generating database sequences in a replicated database environment, comprising:

a group of nodes each hosting an instance of a replicated database, with one node in the group elected as a master node responsible for generating and distributing values for auto-generated values in a column or row of the replicated database;

the master node comprising a sub-range allocating component that divides a sequence space of possible auto-generated values for the column or row into sub-ranges and assigning a sub-range to a particular node in the group of nodes; and

the master node further comprising a demand receiving and value generating component that distributes values of the assigned sub-range to a particular node.

12. The system of claim 11, wherein the master node includes:

a monitoring component that detects a partition or node failure in the group of nodes;

an election component that determines new groups of nodes and elects a new master node in a group of nodes which cannot see an original master node; and

a sequence sub-space generating component that divides the sequence space of possible auto-generated values into sub-spaces for each group of nodes according to the size of each group of nodes.

13. The system of claim 12, wherein the monitoring component of a master node monitors a network periodically to detect a rectification of a network partition fault.

14. The system of claim 12, wherein the master node comprises a sequence sub-space recombining component that recombines the sequence sub-spaces and reasserts the original master node in the master node role should rectification of a network partition fault occur.

15. The system of claim 11, wherein the sub-range allocating component allocates sub-ranges of variable size and nodes which are allocating values faster than other nodes are assigned larger sub-ranges for greater performance.

16. The system of claim 11, wherein the master node assigns and distributes a sub-range of values for itself.

17. The system of claim 11, wherein the nodes of the group of nodes have bi-directional replication for databases where more than one node creates records in a replicated table.

18. A computer program product for generating database sequences, the computer program product comprising a computer readable storage medium having computer-readable program code embodied therewith, the computer-readable program code configured to:

divide, in a replicated database environment having a group of nodes each hosting an instance of a replicated database, with one node in the group elected as a master node responsible for generating and distributing values for auto-generated values in a column or row of the replicated database, a sequence space of possible auto-generated values for the column or row into sub-ranges and assigning a sub-range to a particular node in the group of nodes; and

distribute values of the assigned sub-range to a particular node of the group of nodes.