System and method for flushing bean cache

• US 20050177550A1
• Filed: 04/13/2005
• Published: 08/11/2005
• Est. Priority Date: 08/30/2001
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: BEA Systems Incorporated (Oracle Corporation)
• Inventors: Jacobs, Dean Bernard, Woollen, Rob, White, Seth
• Granted Patent: US 7,293,009 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/2315 Optimistic concurrency control
• 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 16/9574 of access to content, e.g. by caching
• CPC Class Codes: G06Q 20/04 Payment circuits
• CPC Class Codes: G06Q 20/389 Keeping log of transactions for guaranteeing non-repudiation of a transaction
• CPC Class Codes: G07F 19/201 Accessories of ATMs
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04L 67/1097 for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS]
• CPC Class Codes: H04L 67/56 Provisioning of proxy services store-and-forward switching systems in data switching networks H04L12/54
• CPC Class Codes: H04L 67/5682 Policies or rules for updating, deleting or replacing the stored data
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users

Abstract

Servers in a network cluster can each store a copy of a data item in local cache, providing read access to these copies through read-only entity beans. The original data item in the database can be updated through a read/write entity bean one of the cluster servers. That cluster server has access to an invalidation target, which contains identification information relating to copies of the data item stored on servers in the cluster. Once the read/write bean updates the data item in the database, an invalidate request can be sent or multicast to all cluster members, or to any read-only bean or server contained in the invalidation target. Each server or read-only bean receiving the request knows to drop any copy of the data item in local cache, and can request a current copy of the data item from the database.

Claims

1. A method for maintaining a cached copy of a data item in a database, comprising:

receiving a request to access the copy of a data item stored in the database of a first server;

providing read access to the copy of the data item responsive to the request; and

updating the copy from the data item stored in the database according to a refresh mechanism;

repeatedly performing the receiving, providing and updating steps until an invalidate request is received; and

dropping the copy of the data item if identification information included in the invalidate request matches identification information assigned to the copy of the data item.

2. The method of claim 1, further comprising:

causing at least one additional server to drop a locally kept copy of the data item in the database by sending at least one invalidate request to a peer associated with the at least one additional server.

3. The method of claim 1, wherein updating the copy from the data item stored in the database according to a refresh mechanism comprises:

detecting passage of a timeout value associated with the data item; and

refreshing the copy from the data item in the database.

4. The method of claim 2, further comprising:

tagging each one of the at least one invalidate requests with a version number that the at least one additional server can use to determine if all invalidate requests have been received.

5. The method of claim 1, wherein updating the copy from the data item stored in the database according to a refresh mechanism comprises:

receiving a heartbeat message including a latest value for the data item stored in the database and the version number;

determining that an invalidate request message has been missed by comparing the version number from the heartbeat message with a version number of a previously received invalidate message or heartbeat message; and

requesting a copy of an invalidate request message that was missed.

6. The method of claim 5, further comprising:

receiving a message indicating that the invalidate message that was missed is no longer available;

dropping the copy of the data item; and

obtaining a new copy of the data item from the database.

7. The method of claim 2, wherein causing at least one additional server to drop a locally kept copy of the data item in the database by sending at least one invalidate request to a peer associated with the at least one additional server comprises:

sending a multicast invalidate request message to a plurality of servers in a cluster of servers.

8. The method of claim 7, further comprising:

periodically multicasting the invalidate request message across the cluster.

9. The method of claim 1, wherein updating the copy from the data item stored in the database according to a refresh mechanism comprises:

receiving an indication that each of a plurality of data items in the database has been updated to the update values; and

dropping at least one of a plurality of copies of the data items in the database.

10. The method of claim 9, wherein receiving an indication that each of a plurality of data items in the database has been updated to the update values comprises:

receiving a message that includes information for updated primary keys associated with each of a plurality of data items in the database that has been updated to the update values.

11. A computer-readable medium carrying one or more sequences of instructions for maintaining a cached copy of a data item in a database, which instructions, when executed by one or more processors, cause the one or more processors to carry out the steps of:

receiving a request to access the copy of data item stored in the database of a first server;

providing read access to the copy of the data item responsive to the request; and

updating the copy from the data item stored in the database according to a refresh mechanism;

repeatedly performing the receiving, providing and updating steps until an invalidate request is received; and

dropping the copy of the data item if identification information included in the invalidate request matches identification information assigned to the copy of the data item.

12. The computer-readable medium of claim 11, further comprising instructions for carrying out the steps of:

causing at least one additional server to drop a locally kept copy of the data item in the database by sending at least one invalidate request to a peer associated with the at least one additional server.

13. The computer-readable medium of claim 11, wherein the instructions for carrying out the step of updating the copy from the data item stored in the database according to a refresh mechanism further comprise instructions for carrying out the steps of:

detecting passage of a timeout value associated with the data item; and

refreshing the copy from the data item in the database.

14. The computer-readable medium of claim 12, further comprising instructions for carrying out the steps of:

tagging each one of the at least one invalidate requests with a version number that the at least one additional server can use to determine if all invalidate requests have been received.

15. The computer-readable medium of claim 11, wherein the instructions for carrying out the step of updating the copy from the data item stored in the database according to a refresh mechanism further comprise instructions for carrying out the steps of:

receiving a heartbeat message including a latest value for the data item stored in the database and the version number;

determining that an invalidate request message has been missed by comparing the version number from the heartbeat message with a version number of a previously received invalidate message or heartbeat message; and

requesting a copy of an invalidate request message that was missed.

16. The computer-readable medium of claim 15, further comprising instructions for carrying out the steps of:

receiving a message indicating that the invalidate message that was missed is no longer available;

dropping the copy of the data item; and

obtaining a new copy of the data item from the database.

17. The computer-readable medium of claim 12, wherein the instructions for carrying out the step of causing at least one additional server to drop a locally kept copy of the data item in the database by sending at least one invalidate request to a peer associated with the at least one additional server further comprise instructions for carrying out the steps of:

sending a multicast invalidate request message to a plurality of servers in a cluster of servers.

18. The computer-readable medium of claim 17, further comprising instructions for carrying out the steps of:

periodically multicasting the invalidate request message across the cluster.

19. The computer-readable medium of claim 11, wherein the instructions for carrying out the step of updating the copy from the data item stored in the database according to a refresh mechanism further comprise instructions for carrying out the steps of:

receiving an indication that each of a plurality of data items in the database has been updated to the update values; and

dropping at least one of a plurality of copies of the data items in the database.

20. The computer-readable medium of claim 19, wherein the instructions for receiving an indication that each of a plurality of data items in the database has been updated to the update values further comprise instructions for carrying out the steps of:

receiving a message that includes information for updated primary keys associated with each of a plurality of data items in the database that has been updated to the update values.