DECENTRALIZED TRANSACTION COMMIT PROTOCOL

• US 20170177698A1
• Filed: 12/21/2015
• Published: 06/22/2017
• Est. Priority Date: 12/21/2015
• Status: Active Grant

• Current Assignee: SAP SE
• Original Assignee: SAP SE
• Inventors: Park, Chang Gyoo, Kim, Kyu Hwan, Lee, Juchang
• Granted Patent: US 10,235,440 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 16/2315 Optimistic concurrency control
• CPC Class Codes: G06F 16/2455 Query execution
• CPC Class Codes: G06F 16/275 Synchronous replication

Abstract

Technologies are described for facilitating transaction processing within a database environment having first, second, and third database system nodes. In the database system, the first database system node receives from the second database system node a request to precommit a first database transaction. The first database system node stores information for the first database transaction that includes an indication that the second database system node coordinates the committing of the first database transaction. The first database system node receives from the third database system node a request to precommit a second database transaction. The first database system node stores information for the second database transaction that includes an indication that the third database system node coordinates the committing of the second database transaction.

Claims

1. A method, implemented at least in part by a first database system node comprising a processing unit and memory, the first database system node being in communication with at least a second and a third database system nodes, for facilitating database transaction processing within a database environment, the method comprising, at the first database system node:

receiving a request to commit a first database transaction;

sending a request to the second database system node to precommit the first database transaction;

determining a synchronized transaction token;

assigning, based at least in part on the synchronized transaction token, a first transaction token to the first database transaction;

sending the first transaction token to the second database system node;

committing the first database transaction;

acknowledging the commit of the first database transaction to a database client;

receiving a request from the third database system node to precommit a second database transaction; and

adding, to a precommit log, a precommit log entry.

2. The method of claim 1, wherein the precommit log entry comprises an indication that the third database system node coordinates the commit of the second database transaction.

3. The method of claim 1, wherein each of the synchronized transaction token and the first transaction token comprise a commit ID.

4. The method of claim 1, further comprising, at the first database system node:

receiving, from the third database system node, a second transaction token associated with the second database transaction, wherein the second transaction token comprises a timestamp;

determining, based at least in part on the second transaction token, a third transaction token, wherein the third transaction token comprises a timestamp;

assigning the third transaction token to the second database transaction; and

marking the second database transaction as committed.

5. The method of claim 4, wherein determining a third transaction token comprises:

comparing the second transaction token to a local transaction token maintained by the first database system node; and

selecting as, the third transaction token, the more current value of the second transaction token and the local transaction token maintained by the first database system node.

6. The method of claim 4, further comprising receiving a request from the third database system node to commit the second database transaction.

7. The method of claim 4, wherein the third transaction token has the same value as the second transaction token.

8. The method of claim 4, wherein the commit of the second database transaction is acknowledged to a database client by the third database system node.

9. The method of claim 1, wherein the determining a synchronized transaction token comprises:

receiving a local commit timestamp from each of the at least a second and a third database system nodes;

determining a most current value among a local commit timestamp of the first database system node and the respective local commit timestamps from the at least a second and a third database system nodes; and

setting the synchronized transaction token to be the most current value.

10. The method of claim 1, further comprising:

incrementing the synchronized transaction token; and

setting the first transaction token to be the incremented synchronized transaction token.

11. The method of claim 1, wherein the first database system node maintains a first in-doubt transaction table for transactions coordinated by the first database system node, and wherein each of the at least a second and a third database system nodes maintains its own in-doubt transaction table for transactions coordinated by that database system node.

17. The server of claim 1, wherein the first database system node maintains an in-doubt transaction table for transactions coordinated by the first database system node.

12. A server comprising a processing unit and memory, wherein the server is configured to operate a first database system node of a database system, the first database system node being in communication with one or more other database system nodes, wherein the server is further configured to perform database transaction processing comprising:

coordinating, as the first database system node, a commit process for a first database transaction according to a transaction commit protocol, wherein the first database system node acts as coordinator node and each of the one or more other database system nodes involved in the commit act as worker node during the commit process for the first database transaction; and

participating, as the first database system node, in a commit process for a second database transaction according to the transaction commit protocol, wherein the first database system node acts as worker node and one of the one or more other database system nodes acts as coordinator node during the commit process for the second database transaction.

13. The server of claim 12, wherein the coordinating the commit process for the first database transaction includes:

receiving a request to commit the first database transaction;

to each of the one or more other database system nodes involved in the commit, sending a request to precommit the first database transaction;

determining a synchronized transaction token;

assigning, based at least in part of the synchronized transaction token, a first transaction token to the first database transaction;

to each of the one or more other database system nodes involved in the commit, sending the first transaction token;

committing the first database transaction; and

acknowledging the commit of the first database transaction to a database client.

14. The server of claim 13, wherein the first transaction token is the incremented value of the synchronized transaction token.

15. The server of claim 12, wherein the participating in the commit process for the second database transaction includes:

receiving a request to precommit a second database transaction from a given database system node of the one or more other database system node, the given database system node acting as coordinator node during the commit process for the second database transaction;

adding, to a precommit log, a precommit log entry that comprises an indication that the given database system node coordinates the commit of the second database transaction.

16. The server of claim 15, wherein the participating in the commit process for the second database transaction further includes:

receiving a second transaction token from the given database system node, the second transaction token being associated with the second database transaction;

determining, based at least in part on the second transaction token, a third transaction token;

assigning the third transaction token to the second database transaction;

sending an acknowledgment to the third database system node that the third transaction token was assigned to the second database transaction;

receiving a request from the third database system node to commit the second database transaction; and

setting the second database transaction as committed.

18. One or more tangible computer-readable media storing computer-executable instructions for causing a server programmed thereby to perform database transaction processing within a database environment using data manipulation language (DML) statements, the server implementing a first database system node of a database system, the first database system node being in communication with at least a second and a third database system nodes, the database transaction processing comprising:

receiving a request to precommit a first database transaction from the second database system node;

storing transaction information for the first database transaction that comprises an indication that the second database system node coordinates committing the first database transaction;

receiving a request to precommit a second database transaction from the third database system node; and

storing transaction information for the second database transaction that comprises an indication that the third database system node coordinates committing the second database transaction.

19. The one or more tangible computer-readable media of claim 18, wherein the database transaction processing further comprises:

receiving, from a database client, a request to commit a third database transaction; and

coordinating, among the first database system node and the at least a second and third database system nodes, the commit of the third database transaction.

20. The one or more tangible computer-readable media of claim 19, wherein the coordinating includes adding the third database transaction to a table of in-doubt transactions maintained by the first database system node.