Point-in-time recovery¶
Recovering up to particular moment in database’s history can be done with xtrabackup and the binary logs of the server.
Note that the binary log contains the operations that modified the database from a point in the past. You need a full datadir as a base, and then you can apply a series of operations from the binary log to make the data match what it was at the point in time you want.
$ xtrabackup --backup --target-dir=/path/to/backup
$ xtrabackup --prepare --target-dir=/path/to/backup
For more details on these procedures, see Creating a backup and Preparing a backup.
Now, suppose that some time has passed, and you want to restore the database to a certain point in the past, having in mind that there is the constraint of the point where the snapshot was taken.
To find out what is the situation of binary logging in the server, execute the following queries:
mysql> SHOW BINARY LOGS;
Expected output
+------------------+-----------+
| Log_name | File_size |
+------------------+-----------+
| mysql-bin.000001 | 126 |
| mysql-bin.000002 | 1306 |
| mysql-bin.000003 | 126 |
| mysql-bin.000004 | 497 |
+------------------+-----------+
and
mysql> SHOW MASTER STATUS;
Expected output
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000004 | 497 | | |
+------------------+----------+--------------+------------------+
The first query will tell you which files contain the binary log and the second
one which file is currently being used to record changes, and the current
position within it. Those files are stored usually in the datadir
(unless other location is specified when the server is started with the
--log-bin= option).
To find out the position of the snapshot taken, see the
xtrabackup_binlog_info at the backup’s directory:
$ cat /path/to/backup/xtrabackup_binlog_info
Expected output
mysql-bin.000003 57
This will tell you which file was used at moment of the backup for the binary log and its position. That position will be the effective one when you restore the backup:
$ xtrabackup --copy-back --target-dir=/path/to/backup
As the restoration will not affect the binary log files (you may need to adjust file permissions, see Restoring a Backup), the next step is extracting the queries from the binary log with mysqlbinlog starting from the position of the snapshot and redirecting it to a file
$ mysqlbinlog /path/to/datadir/mysql-bin.000003 /path/to/datadir/mysql-bin.000004 \
--start-position=57 > mybinlog.sql
Note that if you have multiple files for the binary log, as in the example, you have to extract the queries with one process, as shown above.
Inspect the file with the queries to determine which position or date
corresponds to the point-in-time wanted. Once determined, pipe it to the
server. Assuming the point is 11-12-25 01:00:00:
$ mysqlbinlog /path/to/datadir/mysql-bin.000003 /path/to/datadir/mysql-bin.000004 \
--start-position=57 --stop-datetime="11-12-25 01:00:00" | mysql -u root -p
and the database will be rolled forward up to that Point-In-Time.
