16.16 Options for Special Backup Types

These options are for backing up database servers that play specific roles in replication, or contain certain kinds of data that require special care in backing up.

• --slave-info

  When backing up a replica server, this option captures information needed to set up an identical replica server. It creates a file meta/ibbackup_slave_info inside the backup directory, containing a CHANGE MASTER statement with the binary log position and name of the binary log file of the source server. This information is also printed in the mysqlbackup output. To set up a new replica for this source, restore the backup data on another server, start a replica server on the backup data, and issue a CHANGE MASTER command with the binary log position saved in the ibbackup_slave_info file. See Section 7.1, “Setting Up a New Replica” for instructions.

  Note

  Only use this option when backing up a replica server. Its behavior is undefined when used on a source or non-replication server.

  This option is not compatible with the --no-locking option; using both options together will make mysqlbackup throw an error.

  This option is not compatible with the --only-innodb or --only-innodb-with-frm options.

• --safe-slave-backup-timeout=SECONDS

  For a statement-based replication (SBR) or a mixed-based replication setup, the option specifies the time (in seconds) mysqlbackup will wait for Slave_open_temp_tables to become “0” (which is true when no temporary tables are open) to complete the backup for a replica server by asserting a global read lock and copies all the non-InnoDB tables. If the duration of the wait exceeds that specified with the option, mysqlbackup times out and throws an error. The wait is for preventing mysqlbackup from finishing a replica backup when there are temporary tables still open. See descriptions in Temporary tables on statement-based replication (SBR) replica for details on how mysqlbackup deals with temporary tables on a replica server.

  In addition, mysqlbackup also runs an initial check at the beginning of a replica backup to see if Slave_open_temp_tables=0 becomes true within the duration set by --safe-slave-backup-timeout. If it does not, mysqlbackup takes it as an early sign that before the backup is completed, some temporary tables are likely to remain open after the timeout limit is exceeded; mysqlbackup then throws an error, instead of continuing with the backup. When that happens, you can either restart the backup with a higher value for --safe-slave-backup-timeout, or retry at a time when fewer temporary tables are being used.

  Default: 300

  Warning

  Proper setting of this value depends on the use case, and it can vary a lot according to the situation. Setting the value for this option either too high or too low will affect adversely the performance of the backup operation:

  • Too high: If you need to wait for a long time for there to be no more temporary tables, the chance is that the change rate for your database is quite high, which means the amount of redo log data to be included in the backup will be large and the restore time for the backup will be long. In such a case, it would have been better to have let mysqlbackup timeout and then restart the backup operation, so the tables are copied in their final states. It is therefore not helpful to set a high timeout value for the option. As a very general rule of thumb: even for busy databases that use many contemporary tables, do not set the value to more than an a few hours.

  • Too low: Setting the wait time value too low would make the backup process time out very easily and when that happens, the process has to be restarted. With a repeating cycle of restarts, the backup might then take a long time to complete, and resources used on the failed backups will be wasted. As a very general rule of thumb, do not set the timeout to below the default value of 300s.

  For a row-based replication (RBR) setup, temporary tables are not replicated onto the replica. Users who are certain that SBR is not occurring for the replica can set --safe-slave-backup-timeout=0, with which mysqlbackup will not check for any open temporary tables before finishing the backup.

• --suspend-at-end

  This option pauses the mysqlbackup command when the backup procedure is close to ending. It creates a file called ibbackup_suspended in the backup log group home directory and waits until you delete that file before proceeding. This option is useful to customize locking behavior and backup of non-InnoDB files through custom scripting.

  All tables are locked before suspending, putting the database into a read-only state, unless you turn off locking with the --no-locking or --no-connection option. The --only-innodb and --only-innodb-with-frm options also prevent the locking step. Because locking all tables could be problematic on a busy server, you might use a combination of --only-innodb and --suspend-at-end to back up only certain InnoDB tables.

• --exec-when-locked="utility arg1 arg2 ..."

  Command-Line Format	--exec-when-locked="utility arg1 arg2 ..."
  Type	String

  You can use this option to run a script that backs up any information that is not included as part of the usual backup. For example, with --exec-when-locked, you can use mysqldump to back up tables from the MEMORY storage engine, which are not on disk.

  Set any variable you want to use within your script before you run mysqlbackup. In the following example, the BACKUP_DIR environment variable is set to point to the current backup directory (quotes are used for the argument of --exec-when-locked, to prevent premature expansion of the variable BACKUP_DIR):

  On Unix or Linux systems:

  export BACKUP_DIR=path_to_backupdir
  mysqlbackup --exec-when-locked="mysqldump mydb t1 > $BACKUP_DIR/t1.sql" other_options mysqlbackup_command

  Or on Windows systems:

  set BACKUP_DIR=path_to_backupdir
  mysqlbackup --exec-when-locked="mysqldump mydb t1 > %BACKUP_DIR%/t1.sql" other_options mysqlbackup_command

  If the utility cannot be executed or returns a non-zero exit status, the whole backup process is cancelled. If you also use the --suspend-at-end option, the utility specified by --exec-when-locked is executed after the suspension is lifted.