Mirror resynchronization of bulk load and append-only tables during online transactions for better repair time to high availability in databases
In a mirrored database system, mirror resynchronization of bulk load and append-only tables during ongoing transactions is optimized for quick repair and high availability by catching up any changes to primary database tables that have not been made to mirror database tables during the transaction itself, and making changes due to ongoing transactions when the databases are synchronized to the resynchronization process.
1. A method of mirror resynchronization of bulk load tables in a mirrored pair of databases comprising a primary database and a mirror database, the method comprising:
creating a bulk load target file;
writing transaction data from an online transaction into the bulk load target file; and
entering a loop of one or more cycles, each cycle comprising:
locking the mirror database;
determining a mirroring state of the primary database and the mirror database;
upon determining that the mirroring state indicates that the primary database and the mirror database are synchronized or that the mirror database is offline, performing first actions comprising:
indicating, in a persistent file system table, that synchronization of the bulk load tables will be performed later;
unlocking the mirror database; and
exiting the loop;
upon determining that the mirroring state indicates otherwise, performing second actions comprising:
unlocking and then opening the mirror database;
sending the transaction data that was flushed to the primary database to the mirror database, the transaction data being flushed by bulk loading the target file to the primary database; and
flushing the mirror database; and
entering a next cycle of the loop.
2. The method of claim 1 , wherein locking the mirror database comprises storing the mirroring state and a sequence number in a mirror lock in an exclusive mode in which values of the mirroring state and the sequence number cannot change.
3. The method of claim 2 , wherein the sequence number is a number that is incremented each time the primary database and the mirror database enter a state indicating that the mirror database is offline.
4. The method of claim 3 , comprising determining the sequence number while the mirror database is in a locked state and prior to creating the bulk load target file.
5. The method of claim 1 , wherein sending the transaction data to the mirror database comprises bulk loading the transaction data to the mirror database.
6. The method of claim 1 , wherein the primary database and the mirror database are stored on different segment nodes of a computer network including a plurality of segment nodes and a master node.
7. A system comprising:
a master node including one or more processors;
a plurality of segment nodes each including one or more processors; and
a non-transitory computer-readable medium storing instructions operable to cause one or more nodes of the system to perform operations of mirror resynchronization of bulk load tables in a mirrored pair of databases comprising a primary database and a mirror database, the operations comprising:
creating a bulk load target file;
writing transaction data from an online transaction into the bulk load target file; and
entering a loop of one or more cycles, each cycle comprising:
locking the mirror database;
determining a mirroring state of the primary database and the mirror database;
upon determining that the mirroring state indicates that the primary database and the mirror database are synchronized or that the mirror database is offline, performing first actions comprising:
indicating, in a persistent file system table, that synchronization of the bulk load tables will be performed later;
unlocking the mirror database; and
exiting the loop;
upon determining that the mirroring state indicates otherwise, performing second actions comprising:
unlocking and then opening the mirror database;
sending the transaction data that was flushed to the primary database to the mirror database, the transaction data being flushed by bulk loading the target file to the primary database; and
flushing the mirror database; and
entering a next cycle of the loop.
8. The system of claim 7 , wherein locking the mirror database comprises storing the mirroring state and a sequence number in a mirror lock in an exclusive mode in which values of the mirroring state and the sequence number cannot change.
9. The system of claim 8 , wherein the sequence number is a number that is incremented each time the primary database and the mirror database enter a state indicating that the mirror database is offline.
10. The system of claim 9 , the operations comprising determining the sequence number while the mirror database is in a locked state and prior to creating the bulk load target file.
11. The system of claim 7 , wherein sending the transaction data to the mirror database comprises bulk loading the transaction data to the mirror database.
12. The system of claim 7 , wherein the primary database and the mirror database are stored on different segment nodes of the system.
13. A non-transitory computer-readable medium storing instructions operable to cause one or more processors to perform operations of mirror resynchronization of bulk load tables in a mirrored pair of databases comprising a primary database and a mirror database, the operations comprising:
creating a bulk load target file;
writing transaction data from an online transaction into the bulk load target file; and
entering a loop of one or more cycles, each cycle comprising:
locking the mirror database;
determining a mirroring state of the primary database and the mirror database;
upon determining that the mirroring state indicates that the primary database and the mirror database are synchronized or that the mirror database is offline, performing first actions comprising:
indicating, in a persistent file system table, that synchronization of the bulk load tables will be performed later;
unlocking the mirror database; and
exiting the loop;
upon determining that the mirroring state indicates otherwise, performing second actions comprising:
unlocking and then opening the mirror database;
sending the transaction data that was flushed to the primary database to the mirror database, the transaction data being flushed by bulk loading the target file to the primary database; and
flushing the mirror database; and
entering a next cycle of the loop.
14. The non-transitory computer-readable medium of claim 13 , wherein locking the mirror database comprises storing the mirroring state and a sequence number in a mirror lock in an exclusive mode in which values of the mirroring state and the sequence number cannot change.
15. The non-transitory computer-readable medium of claim 14 , wherein the sequence number is a number that is incremented each time the primary database and the mirror database enter a state indicating that the mirror database is offline.
16. The non-transitory computer-readable medium of claim 15 , the operations comprising determining the sequence number while the mirror database is in a locked state and prior to creating the bulk load target file.
17. The non-transitory computer-readable medium of claim 13 , wherein sending the transaction data to the mirror database comprises bulk loading the transaction data to the mirror database.
18. The non-transitory computer-readable medium of claim 13 , wherein the primary database and the mirror database are stored on different segment nodes of a computer network including a plurality of segment nodes and a master node.