.. _mariadb-backup-and-restore:

===================================
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``:

.. code-block:: console

   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:

.. code-block:: console

   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:

.. code-block:: console

   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:

.. code-block:: console

   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``.

.. code-block:: console

   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.