Point-In-Time recovery

Recovering up to particular moment in database’s history can be done with innobackupex 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: it’s acts as a “redo log”. You need a snapshot of the past from which “redo” the operations up to the Point-In-Time you want.

For taking the snapshot, we will use innobackupex for a full backup:

$ innobackupex /path/to/backup --no-timestamp

(the --no-timestamp option is for convenience in this example) and we will prepare it to be ready for restoration:

$ innobackupex --apply-log /path/to/backup

For more details on these procedures, see Creating a Backup with innobackupex and Preparing a Full Backup with innobackupex.

Now, suppose that 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;
+------------------+-----------+
| 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;
+------------------+----------+--------------+------------------+
| 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 been used and its actual position. 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
mysql-bin.000003      57

This will tell you which file was used at moment of the backup for the binary log and it position. That position will be the effective one when you restore the backup:

$ innobackupex --copy-back /path/to/backup

As the restoration will not affect the binary log files (you may need to adjust file permissions, see Restoring a Full Backup with innobackupex), 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 process all of them 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.

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