Point-In-Time recovery

ゝ一纸荒年。 2022-09-21 01:27 78阅读 0赞

本文转载自：http://www.percona.com/doc/percona-xtrabackup/2.1/innobackupex/pit\_recovery\_ibk.html

# 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. 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.

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

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
    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:

$ 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 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.

注：近期参加MySQL运维学习，老师推荐该文章作为学习和技术提高的扩展阅读，先记录到自己的博客中，随后慢慢消化、学习、提高。本文章与“日志系统”主题相关。

[datadir]: http://www.percona.com/doc/percona-xtrabackup/2.1/glossary.html#term-datadir
[Creating a Backup with innobackupex]: http://www.percona.com/doc/percona-xtrabackup/2.1/innobackupex/creating_a_backup_ibk.html
[Preparing a Full Backup with innobackupex]: http://www.percona.com/doc/percona-xtrabackup/2.1/innobackupex/preparing_a_backup_ibk.html
[Restoring a Full Backup with innobackupex]: http://www.percona.com/doc/percona-xtrabackup/2.1/innobackupex/restoring_a_backup_ibk.html