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Percona TokuBackup

Starting with Percona Server for MySQL 8.0.28-19 (2022-05-12), the TokuDB storage engine is no longer supported. For more information, see the TokuDB Introduction and TokuDB version changes.

Percona TokuBackup is an open-source hot backup utility for MySQL servers running the TokuDB storage engine (including Percona Server for MySQL and MariaDB). It does not lock your database during backup. The TokuBackup library intercepts system calls that write files and duplicates the writes to the backup directory.

Note

This feature is currently considered tech preview and should not be used in a production environment.

Installing From Binaries

The installation of TokuBackup can be performed with the ps-admin script.

To install Percona TokuBackup complete the following steps. Run the following commands as root or by using the sudo command.

  1. Run ps-admin.enable-tokubackup to add the preload-hotbackup option into [mysqld_safe] section of my.cnf.

    The output could be:

    Checking SELinux status... INFO: SELinux is disabled.

Checking if preload-hotbackup option is already set in config file... INFO: Option preload-hotbackup is not set in the config file.

Checking TokuBackup plugin status... INFO: TokuBackup plugin is not installed.

Adding preload-hotbackup option into /etc/my.cnf INFO: Successfully added preload-hotbackup option into /etc/my.cnf PLEASE RESTART MYSQL SERVICE AND RUN THIS SCRIPT AGAIN TO FINISH INSTALLATION!
    2. Restart mysql service: :bash:

        $ service mysql restart

  2. Run ps-admin –enable-tokubackup again to finish the installation of the TokuBackup plugin.

    ```text Checking SELinux status… INFO: SELinux is disabled.

    Checking if preload-hotbackup option is already set in config file… INFO: Option preload-hotbackup is set in the config file.

    Checking TokuBackup plugin status… INFO: TokuBackup plugin is not installed.

    Checking if Percona Server is running with libHotBackup.so preloaded… INFO: Percona Server is running with libHotBackup.so preloaded.

    Installing TokuBackup plugin… INFO: Successfully installed TokuBackup plugin.

Making a Backup

To run Percona TokuBackup, the backup destination directory must exist, be writable and owned by the same user under which MySQL server is running (usually mysql) and empty.

Once this directory is created, the backup can be run using the following command:

mysql> set tokudb_backup_dir='/path_to_empty_directory';

Note

Setting the tokudb_backup_dir variable automatically starts the backup process to the specified directory. Percona TokuBackup will take full backup each time, currently there is no incremental backup option

If you get any error on this step (e.g. caused by some misconfiguration), the Reporting Errors section explains how to find out the reason.

Restoring From Backup

Percona TokuBackup does not have any functionality for restoring a backup. You can use rsync or cp to restore the files. You should check that the restored files have the correct ownership and permissions.

NOTE: Make sure that the datadir is empty and that MySQL server is shut down before restoring from backup. You can’t restore to a datadir of a running mysqld instance (except when importing a partial backup).

The following example shows how you might use the rsync command to restore the backup:

$ rsync -avrP /data/backup/ /var/lib/mysql/

Since attributes of files are preserved, in most cases you will need to change their ownership to mysql before starting the database server. Otherwise, the files will be owned by the user who created the backup.

$ chown -R mysql:mysql /var/lib/mysql

If you have changed default TokuDB data directory (tokudb_data_dir) or TokuDB log directory (tokudb_log_dir) or both of them, you will see separate folders for each setting in backup directory after taking backup. You’ll need to restore each folder separately:

$ rsync -avrP /data/backup/mysql_data_dir/ /var/lib/mysql/
$ rsync -avrP /data/backup/tokudb_data_dir/ /path/to/original/tokudb_data_dir/
$ rsync -avrP /data/backup/tokudb_log_dir/ /path/to/original/tokudb_log_dir/
$ chown -R mysql:mysql /var/lib/mysql
$ chown -R mysql:mysql /path/to/original/tokudb_data_dir
$ chown -R mysql:mysql /path/to/original/tokudb_log_dir

Advanced Configuration

Monitoring Progress

TokuBackup updates the PROCESSLIST state while the backup is in progress. You can see the output by running SHOW PROCESSLIST or SHOW FULL PROCESSLIST.

Excluding Source Files

You can exclude certain files and directories based on a regular expression set in the tokudb_backup_exclude session variable. If the source file name matches the excluded regular expression, then the source file is excluded from backup.

For example, to exclude all lost+found directories from backup, use the following command:

mysql> SET tokudb_backup_exclude='/lost\\+found($|/)';

Note

The server pid file is excluded by default. If you’re providing your own additions to the exclusions and have the pid file in the default location, you will need to add the mysqld_safe.pid entry.

Throttling Backup Rate

You can throttle the backup rate using the tokudb_backup_throttle session-level variable. This variable throttles the write rate in bytes per second of the backup to prevent TokuBackup from crowding out other jobs in the system. The default and max value is 18446744073709551615.

mysql> SET tokudb_backup_throttle=1000000;

Restricting Backup Target

You can restrict the location of the destination directory where the backups can be located using the tokudb_backup_allowed_prefix system-level variable. Attempts to backup to a location outside of the specified directory or its children will result in an error.

The default is null, backups have no restricted locations. This read-only variable can be set in the my.cnf configuration file and displayed with the SHOW VARIABLES command:

mysql> SHOW VARIABLES LIKE 'tokudb_backup_allowed_prefix';

The output could be:

+------------------------------+-----------+
| Variable_name                | Value     |
+------------------------------+-----------+
| tokudb_backup_allowed_prefix | /dumpdir  |
+------------------------------+-----------+

Reporting Errors

Percona TokuBackup uses two variables to capture errors. They are tokudb_backup_last_error and tokudb_backup_last_error_string. When TokuBackup encounters an error, these will report on the error number and the error string respectively. For example, the following output shows these parameters following an attempted backup to a directory that was not empty:

mysql> SET tokudb_backup_dir='/tmp/backupdir';

The output could be:

ERROR 1231 (42000): Variable 'tokudb_backup_dir' can't be set to the value of '/tmp/backupdir'

mysql> SELECT @@tokudb_backup_last_error;
+----------------------------+
| @@tokudb_backup_last_error |
+----------------------------+
|                         17 |
+----------------------------+

mysql> SELECT @@tokudb_backup_last_error_string;

The output could be:

+---------------------------------------------------+
| @@tokudb_backup_last_error_string                 |
+---------------------------------------------------+
| tokudb backup couldn't create needed directories. |
+---------------------------------------------------+

Using TokuDB Hot Backup for Replication

TokuDB Hot Backup makes a transactionally consistent copy of the TokuDB files while applications read and write to these files. The TokuDB hot backup library intercepts certain system calls that writes files and duplicates the writes on backup files while copying files to the backup directory. The copied files contain the same content as the original files.

TokuDB Hot Backup also has an API. This API includes the start capturing and stop capturing commands. The “capturing” command starts the process, when a portion of a file is copied to the backup location, and this portion is changed, these changes are also applied to the backup location.

Replication often uses backup replication to create replicas. You must know the last executed global transaction identifier (GTID) or binary log position both for the replica and source configuration.

To lock tables, use FLUSH TABLE WITH READ LOCK or use the smart locks like LOCK TABLES FOR BACKUP or LOCK BINLOG FOR BACKUP.

During the copy process, the binlog is flushed, and the changes are copied to backup by the “capturing” mechanism. After everything has been copied, and the “capturing” mechanism is still running, use the LOCK BINLOG FOR BACKUP. After this statement is executed, the binlog is flushed, the changes are captured, and any queries that could change the binlog position or executed GTID are blocked.

After this command, we can stop capturing and retrieve the last executed GTID or binlog log position and unlock the binlog.

After a backup is taken, there are the following files in the backup directory:

  • tokubackup_slave_info

  • tokubackup_binlog_info

These files contain information for replica and source. You can use this information to start a new replica from the source or replica.

The SHOW MASTER STATUS and SHOW SLAVE STATUS commands provide the information.

Important

As of MySQL 8.0.22, the SHOW SLAVE STATUS statement is deprecated. Use SHOW REPLICA STATUS instead.

In specific binlog formats, a binary log event can contain statements that produce temporary tables on the replica side, and the result of further statements may depend on the temporary table content. Typically, temporary tables are not selected for backup because they are created in a separate directory. A backup created with temporary tables created by binlog events can cause issues when restored because the temporary tables are not restored. The data may be inconsistent.

The following system variables –tokudb-backup-safe-slave, which enables or disables the safe-slave mode, and –tokudb-backup-safe-slave-timeout, which defines the maximum amount of time in seconds to wait until temporary tables disappear. The safe-slave mode, when used with LOCK BINLOG FOR BACKUP, the replica SQL thread is stopped and checked to see if temporary tables produced by the replica exist or do not exist. If temporary tables exist, the replica SQL thread is restarted until there are no temporary tables or a defined timeout is reached.

You should not use this option for group-replication.

Create a Backup with a Timestamp

If you plan to store more than one backup in a location, you should add a timestamp to the backup directory name.

A sample Bash script has this information:

#!/bin/bash

tm=$(date "+%Y-%m-%d-%H-%M-%S");
backup_dir=$PWD/backup/$tm;
mkdir -p $backup_dir;
bin/mysql -uroot -e "set tokudb_backup_dir='$backup_dir'"

Limitations and known issues

  • You must disable InnoDB asynchronous IO if backing up InnoDB tables with TokuBackup. Otherwise you will have inconsistent, unrecoverable backups. The appropriate setting is innodb_use_native_aio=0.

  • To be able to run Point-In-Time-Recovery you’ll need to manually get the binary log position.

  • Transactional storage engines (TokuDB and InnoDB) will perform recovery on the backup copy of the database when it is first started.

  • Tables using non-transactional storage engines (MyISAM) are not locked during the copy and may report issues when starting up the backup. It is best to avoid operations that modify these tables at the end of a hot backup operation (adding/changing users, stored procedures, etc.).

  • The database is copied locally to the path specified in /path/to/backup. This folder must exist, be writable, be empty, and contain enough space for a full copy of the database.

  • TokuBackup always makes a backup of the MySQL datadir and optionally the tokudb_data_dir, tokudb_log_dir, and the binary log folder. The latter three are only backed up separately if they are not the same as or contained in the MySQL datadir. None of these three folders can be a parent of the MySQL datadir.

  • No other directory structures are supported. All InnoDB, MyISAM, and other storage engine files must be within the MySQL datadir.

  • TokuBackup does not follow symbolic links.

  • TokuBackup does not backup MySQL configuration file(s).

  • TokuBackup does not backup tablespaces if they are out of datadir.

  • Due to upstream bug #80183, TokuBackup can’t recover backed-up table data if backup was taken while running OPTIMIZE TABLE or ALTER TABLE ... TABLESPACE.

  • TokuBackup doesn’t support incremental backups.

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Last update: 2024-03-22