SYSTEM FOR MAINTAINING A DISTRIBUTED DATABASE USING LEASES

• US 20110225120A1
• Filed: 03/11/2010
• Published: 09/15/2011
• Est. Priority Date: 03/11/2010
• Status: Abandoned Application

• Current Assignee: Oath Inc. (Verizon Communications Inc.)
• Original Assignee: Yahoo! Inc. (Apollo Global Management, Inc.)
• Inventors: Kadambi, Sudarshan V., Cooper, Brian F.
• Application Number:
  US12/722,093
• Publication Number:
  US 20110225120A1
• Time in Patent Office: Days
• US Class Current: 707/610
• CPC Class Codes: G06F 16/273 Asynchronous replication or reconciliation

Abstract

A system and method for maintaining a database with a plurality of replicas that are geographically distributed. A plurality of tables are stored in a first replica, each table including a plurality of records. The system identifying if the record is a stub and requesting a lease from a second replica designated as master for the record if the record is a stub. The system receiving a copy of the record from the second replica and storing data fields of the record in the first replica after receiving the lease.

Claims

1. A system for maintaining a database with a plurality of replicas that are geographically distributed, the system comprising:

a storage unit including a plurality of tables in a first replica of the plurality of replicas, each table of the plurality of tables comprising a plurality of records; and

wherein the storage unit identifies if the record is a stub and requests a lease from a second replica designated as master for the record, the storage unit receiving a copy of the record from the second replica and storing data fields in response to the lease request.

2. The system according to claim 1, wherein the second replica determines if any constraint rules will be violated by storing data fields in the first replica

3. The system according to claim 1, wherein the lease is a permission to store the record that has a limited time.

4. The system according to claim 3, wherein storage unit requests a renewal of the lease if a read request for the record is received and the limited time has expired.

5. The system according to claim 4, wherein the storage unit purges the record and replaces the record with a stub if the renewal is denied.

6. The system according to claim 1, wherein the storage unit sends a message to the second replica offering surrender of the lease if an update is received and the limited time has expired.

7. The system according to claim 1, wherein storage unit determines the average latency for delivering a record to a client and requests a lease based on the average latency.

8. The system according to claim 7, wherein storage unit requests a lease if the average latency is above a predetermined latency.

9. The system according to claim 1, wherein the storage unit requests a lease if the ratio of local reads to global updates is above a predetermined ratio.

10. A method for maintaining a database with a plurality of replicas that are geographically distributed, the method comprising the steps of:

storing a plurality of tables in a first replica of the plurality of replicas, each table of the plurality of tables comprising a plurality of records;

identifying if the record is a stub;

requesting a lease from a second replica designated as master for the record;

receiving a copy of the record from the second replica; and

storing data fields of the record in the first replica.

11. The method according to claim 10, wherein the second replica determines if any constraint rules will be violated by storing data fields in the first replica

12. The method according to claim 10, wherein the lease is a permission to store the record that has a limited time.

13. The method according to claim 12, further comprising requesting a renewal of the lease if a read request for the record is received and the limited time has expired.

14. The method according to claim 10, further comprising sending a message to the second replica offering surrender of the lease if an update is received and the limited time has expired.

15. The method according to claim 10, further comprising determining the average latency for delivering a record to a client and requests a lease based on the average latency.

16. A computer readable medium having stored therein instructions executable by a programmed processor for maintaining a database with a plurality of replicas that are geographically distributed, the computer readable medium comprising instructions for:

storing a plurality of tables in a first replica of the plurality of replicas, each table of the plurality of tables comprising a plurality of records;

identifying if the record is a stub;

requesting a lease from a second replica designated as master for the record

receiving a copy of the record from the second replica; and

storing data fields of the record in the first replica.

17. The computer readable medium according to claim 16, wherein the second replica determines if any constraint rules will be violated by storing data fields in the first replica

18. The computer readable medium according to claim 16, wherein the lease is a permission to store the record that has a limited time.

19. The computer readable medium according to claim 18, further comprising requesting a renewal of the lease if a read request for the record is received and the limited time has expired.

20. The computer readable medium according to claim 16, further comprising sending a message to the second replica offering surrender of the lease if an update is received and the limited time has expired.

21. The computer readable medium according to claim 16, further comprising determining the average latency for delivering a record to a client and requests a lease based on the average latency.