Data is, by far, the most valuable part of a system. Having a backup done systematically and available for a rapid recovery in case of failure is admittedly essential to a system. However, it is not common practice because of its costs, infrastructure needed or even the boredom associated to the task. Xtrabackup is designed to solve this problem.
You can have almost real-time backups in 6 simple steps by setting up a replication environment with XtraBackup.
Percona XtraBackup is a tool for backing up your data extremely easy and without interruption. It performs “hot backups” on unmodified versions of MySQL servers (5.0, 5.1 and 5.5), as well as MariaDB and Percona Servers. It is a totally free and open source software distributed only under the GPLv2 license.
Setting up a slave for replication with XtraBackup is really a very straightforward procedure. In order to keep it simple, here is a list of the things you need to follow the steps without hassles:
At TheMaster, issue the following to a shell:
TheMaster$ innobackupex --user=yourDBuser --password=MaGiCdB1 /path/to/backupdir
After this is finished you should get:
innobackupex: completed OK!
This will make a copy of your MySQL data dir to the /path/to/backupdir/$TIMESTAMP. You have told XtraBackup (through the innobackupex script) to connect to the database server using your database user and password, and do a hot backup of all your data in it (all MyISAM, InnoDB tables and indexes in them).
In order for snapshot to be consistent you need to prepare the data:
TheMaster$ innobackupex --user=yourDBuser --password=MaGiCdB1 / --apply-log /path/to/backupdir/$TIMESTAMP/
You need to select path where your snapshot has been taken, for example /home/backups/2012-01-16_11-14-43. If everything is ok you should get the same OK message. Now the transaction logs are applied to the data files, and new ones are created: your data files are ready to be used by the MySQL server.
XtraBackup knows where your data is by reading your my.cnf. If you have your configuration file in a non-standard place, you should use the flag --defaults-file =/location/of/my.cnf.
If you want to skip writing the username/password every time you want to access the MySQL, you can set it up in your $HOME folder. Just edit .my.cnf and add:
[client] user=root pass=MaGiCdB1
This is will give you root access to MySQL.
Use rsync or scp to copy the data from Master to Slave. If you’re syncing the data directly to slave’s data directory it’s advised to stop the mysqld there.
TheMaster$ rsync -avprP -e ssh /path/to/backupdir/$TIMESTAMP TheSlave:/path/to/mysql/
After data has been copied you can back up the original or previously installed MySQL datadir:
TheSlave$ mv /path/to/mysql/datadir /path/to/mysql/datadir_bak
and move the snapshot from TheMaster in its place:
TheSlave$ mv /path/to/mysql/$TIMESTAMP /path/to/mysql/datadir
After you copy data over, make sure MySQL has proper permissions to access them.
TheSlave$ chown mysql:mysql /path/to/mysql/datadir
In case the ibdata and iblog files are located in different directories outside of the datadir, you will have to put them in their proper place after the logs have been applied.
Add the appropriate grant in order for slave to be able to connect to master:
TheMaster|mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'$slaveip' IDENTIFIED BY '$slavepass';
Also make sure that firewall rules are correct and that TheSlave can connect to TheMaster.
First copy the my.cnf file from TheMaster to TheSlave:
TheSlave$ scp user@TheMaster:/etc/mysql/my.cnf /etc/mysql/my.cnf
then change the following options in /etc/mysql/my.cnf:
and start/restart mysqld on TheSlave.
In case you’re using init script to start mysqld, be sure that the password for that user has been updated and it’s the same as one on TheMaster. For example, Debian and Ubuntu use debian-sys-maint user to do that. Password can be seen and updated in /etc/mysql/debian.cnf.
Look at the content of the file xtrabackup_binlog_info, it will be something like:
TheSlave$ cat /var/lib/mysql/xtrabackup_binlog_info TheMaster-bin.000001 481
Execute the CHANGE MASTER statement on a MySQL console and use the username and password you’ve set up in STEP 3:
TheSlave|mysql> CHANGE MASTER TO MASTER_HOST='$masterip', MASTER_USER='repl', MASTER_PASSWORD='$slavepass', MASTER_LOG_FILE='TheMaster-bin.000001', MASTER_LOG_POS=481;
and start the slave:
TheSlave|mysql> START SLAVE;
You should check that everything went OK with:
TheSlave|mysql> SHOW SLAVE STATUS \G ... Slave_IO_Running: Yes Slave_SQL_Running: Yes ... Seconds_Behind_Master: 13 ...
Both IO and SQL threads need to be running. The Seconds_Behind_Master means the SQL currently being executed has a current_timestamp of 13 seconds ago. It is an estimation of the lag between TheMaster and TheSlave. Note that at the beginning, a high value could be shown because TheSlave has to “catch up” with TheMaster.
You can use this procedure with slight variation to add new slaves to a master. We will use XtraBackup to clone an already configured slave. We will continue using the previous scenario for convenience but we will add TheNewSlave to the plot.
At TheSlave, do a full backup:
TheSlave$ innobackupex --user=yourDBuser --password=MaGiCiGaM / --slave-info /path/to/backupdir
By using the --slave-info Xtrabackup creates additional file called xtrabackup_slave_info.
Apply the logs:
TheSlave$ innobackupex --apply-log --use-memory=2G /path/to/backupdir/$TIMESTAMP/
Copy the directory from the TheSlave to TheNewSlave:
rsync -avprP -e ssh /path/to/backupdir/$TIMESTAMP TheNewSlave:/path/to/mysql/datadir
Add additional grant on the master:
TheMaster|mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'$newslaveip' IDENTIFIED BY '$slavepass';
Copy the configuration file from TheSlave:
TheNEWSlave$ scp user@TheSlave:/etc/mysql/my.cnf /etc/mysql/my.cnf
Make sure you change the server-id variable in /etc/mysql/my.cnf to 3 and disable the replication on start:
After setting server_id, start mysqld.
Fetch the master_log_file and master_log_pos from the file xtrabackup_slave_info, execute the statement for setting up the master and the log file for The NEW Slave:
TheNEWSlave|mysql> CHANGE MASTER TO MASTER_HOST='$masterip' MASTER_USER='repl', MASTER_PASSWORD='$slavepass', MASTER_LOG_FILE='TheMaster-bin.000001', MASTER_LOG_POS=481;
and start the slave:
TheSlave|mysql> START SLAVE;
If both IO and SQL threads are running when you check the TheNewSlave, server is replicating TheMaster.
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