MariaDB database backup and restore

Kolla-Ansible can facilitate either full or incremental backups of data hosted in MariaDB. It achieves this using Percona’s Xtrabackup, a tool designed to allow for ‘hot backups’ - an approach which means that consistent backups can be taken without any downtime for your database or your cloud.

Note

By default, backups will be performed on the first node in your Galera cluster or on the MariaDB node itself if you just have the one. Backup files are saved to a dedicated Docker volume - mariadb_backup - and it’s the contents of this that you should target for transferring backups elsewhere.

Enabling Backup Functionality

For backups to work, some reconfiguration of MariaDB is required - this is to enable appropriate permissions for the backup client, and also to create an additional database in order to store backup information.

Firstly, enable backups via globals.yml:

enable_xtrabackup: "yes"

Then, kick off a reconfiguration of MariaDB:

kolla-ansible -i INVENTORY reconfigure -t mariadb

Once that has run successfully, you should then be able to take full and incremental backups as described below.

Backup Procedure

To perform a full backup, run the following command:

kolla-ansible -i INVENTORY mariadb_backup

Or to perform an incremental backup:

kolla-ansible -i INVENTORY mariadb_backup --incremental

Kolla doesn’t currently manage the scheduling of these backups, so you’ll need to configure an appropriate scheduler (i.e cron) to run these commands on your behalf should you require regular snapshots of your data. A suggested schedule would be:

  • Daily full, retained for two weeks

  • Hourly incremental, retained for one day

Backups are performed on your behalf on the designated database node using permissions defined during the configuration step; no password is required to invoke these commands.

Furthermore, backup actions can be triggered from a node with a minimal installation of Kolla-Ansible, specifically one which doesn’t require a copy of passwords.yml. This is of note if you’re looking to implement automated backups scheduled via a cron job.

Restoring backups

Owing to the way in which XtraBackup performs hot backups, there are some steps that must be performed in order to prepare your data before it can be copied into place for use by MariaDB. This process is currently manual, but the Kolla XtraBackup image includes the tooling necessary to successfully prepare backups. Two examples are given below.

Full

For a full backup, start a new container using the XtraBackup image with the following options on the master database node:

docker run -it --volumes-from mariadb --name dbrestore \
   -v mariadb_backup:/backup kolla/centos-binary-xtrabackup:rocky \
   /bin/bash
cd /backup
mkdir -p /restore/full
cat mysqlbackup-04-10-2018.xbc.xbs | xbstream -x -C /restore/full/
innobackupex --decompress /restore/full
find /restore -name *.qp -exec rm {} \;
innobackupex --apply-log /restore/full

Then stop the MariaDB instance, delete the old data files (or move them elsewhere), and copy the backup into place:

docker stop mariadb
rm -rf /var/lib/mysql/* /var/lib/mysql/.*
innobackupex --copy-back /restore/full

Then you can restart MariaDB with the restored data in place:

docker start mariadb
docker logs mariadb
81004 15:48:27 mysqld_safe WSREP: Running position recovery with --log_error='/var/lib/mysql//wsrep_recovery.BDTAm8' --pid-file='/var/lib/mysql//scratch-recover.pid'
181004 15:48:30 mysqld_safe WSREP: Recovered position 9388319e-c7bd-11e8-b2ce-6e9ec70d9926:58

Incremental

This starts off similar to the full backup restore procedure above, but we must apply the logs from the incremental backups first of all before doing the final preparation required prior to restore. In the example below, I have a full backup - mysqlbackup-06-11-2018-1541505206.qp.xbc.xbs, and an incremental backup, incremental-11-mysqlbackup-06-11-2018-1541505223.qp.xbc.xbs.

docker run -it --volumes-from mariadb --name dbrestore \
   -v mariadb_backup:/backup kolla/centos-binary-xtrabackup:rocky \
   /bin/bash
cd /backup
mkdir -p /restore/full
mkdir -p /restore/inc/11
cat mysqlbackup-06-11-2018-1541505206.qp.xbc.xbs | xbstream -x -C /restore/full/
cat incremental-11-mysqlbackup-06-11-2018-1541505223.qp.xbc.xbs | xbstream -x -C /restore/inc/11
innobackupex --decompress /restore/full
innobackupex --decompress /restore/inc/11
find /restore -name *.qp -exec rm {} \;
innobackupex --apply-log --redo-only /restore/full
innobackupex --apply-log --redo-only --incremental-dir=/restore/inc/11 /restore/full
innobackupex --apply-log /restore/full

At this point the backup is prepared and ready to be copied back into place, as per the previous example.